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User Manual
p
gigaBERT1400
1400 Mb/s Bit Error Rate Tester
Generator and Analyzer
071-0590-00
This document supports firmware version 2.2 and above.
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WARRANTY
Tektronix warrants that this product will be free from defects in materials and workmanship for a
period of one (1) year from the date of shipment. If any such product proves defective during this
warranty period, Tektronix, at its option, either will repair the defective product without charge
for parts and labor, or will provide a replacement in exchange for the defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect
before the expiration of the warranty period and make suitable arrangements for the performance
of service. Customer shall be responsible for packaging and shipping the defective product to the
service center designated by Tektronix, with shipping charges prepaid. Tektronix shall pay for
the return of the product to Customer if the shipment is to a location within the country in which
Tektronix service center is located. Customer shall be responsible for paying all shipping charges,
duties, taxes, and any other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or
improper or inadequate maintenance and care. Tektronix shall not be obligated to furnish service
under warranty a) to repair damage resulting from attempts by personnel other than Tektronix
representatives to install, repair or service the product; b) to repair damage resulting from
improper user or connection to incompatible equipment; or c) to service a product that has been
modified or integrated with other products when the effect of such modification or integration
increases the time or difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX WITH RESPECT TO THIS PRODUCT
IN LIEU OF ANY OTHER WARRANTIES, EXPRESSED OR IMPLIED. TEKTRONIX
AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TEKTRONIX’
RESPONSIBILITY TO REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE
SOLE AND EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR BREACH
OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS WILL NOT BE LIABLE
FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
IRRESPECTIVE OF WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE
NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.
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How to Reach Customer Service
If you have any questions regarding the operation, maintenance, repair,
or application of your Tektronix equipment, contact your local sales
and service office. For a complete list of the Worldwide Sales and
Service Offices contact (800) 426-2200.
Tektronix provides high quality Technical Support on applications,
operation, measurement specifications, hardware, and software by
expert application engineers. For Applications Support, call the
Customer Support Center listed below.
Mailing
Tektronix, Inc.
Attn. Customer Service
Address
Measurement Business Division
P.O. Box 500
Beaverton, Oregon 97077-0001
USA
Customer
and Sales
Support
Center
Hours are 6:00 AM to 5:00 PM,
Pacific Time.
800-TEK-WIDE
or
800-835-9433 Ext 2400
After hours Voice Mail is available.
Direct
Fax
503-627-2400
503-627-5695
E-Mail
Web Site
http://www.tek.com
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Table of Contents
Safety..................................................................................................
xii
Getting Started
Features...............................................................................................
Ordering Information............................................................................
gigaBERT comparison chart..................................................................
Initial Self-Check Procedure .................................................................
1-1
1-4
1-5
1-7
Operating Basics
Functional Overview.......................................................................................
BERT Basics - GB1400 ........................................................................
Controls, Indicators, and Connectors......................................................
Display Formats ...................................................................................
Outputs & Inputs..................................................................................
Generator OUTPUT .......................................................................
Generator CLOCK .........................................................................
Generator OUTPUT (Set-up)...........................................................
Generator Rear Panel......................................................................
Changing the Line Fuse ..................................................................
Analyzer INPUT............................................................................
Analyzer MONITOR......................................................................
Analyzer Rear Panel.......................................................................
Changing the Line Fuse ..................................................................
Connectors, Terminations and Levels ..............................................
Controls & Indicators............................................................................
Power Switches..............................................................................
Unit Mounting ...............................................................................
Unit Cooling ..................................................................................
View Angle and Panel Lock Keys ...................................................
Reset to Factory Default..................................................................
GPIB Controls................................................................................
Pattern Controls and Function Keys .................................................
Function (Soft) Keys (F1, F2, F3, F4)...............................................
2-1
2-2
2-4
2-6
2-9
2-9
2-10
2-11
2-12
2-12
2-13
2-14
2-15
2-15
2-16
2-18
2-18
2-18
2-18
2-18
2-18
2-19
2-20
2-21
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Table of Contents
Generator ERROR INJECT ............................................................
2-22
2-23
2-24
2-25
2-25
2-26
2-27
2-27
2-29
2-30
2-38
Analyzer INPUT............................................................................
Analyzer Error History....................................................................
Analyzer ERROR DETECTION .....................................................
Analyzer SYNC Controls ................................................................
Burst Mode Option ...............................................................................
Burst Mode Usage..........................................................................
Specifications for Burst Mode .........................................................
PECL Option for GB1400 Tx ................................................................
Tutorial...........................................................................................................
Applications ....................................................................................................
Method for Very Fast Automatic RX Synchronization
and Eye Width Measurement.........................................................
2-38
2-46
2-47
2-48
2-49
GB700/ GB1400 Optical Component Test........................................
Fibre Channel Link Testing Parallel and High-Speed Serial...............
Testing QPSK Modems, I & Q........................................................
QPSK BER Testing using PRBS Data for 2-Channel I & Q...............
Reference
Menu Overview....................................................................................
Functions common to TX and RX..........................................................
AC Power......................................................................................
Selecting 115 VAC or 230 VAC operation .......................................
Turning Instrument Power ON/OFF.................................................
LCD Viewing Angle .......................................................................
Recalling Default Setup...................................................................
Locking the Front Panel..................................................................
Selecting a Pattern................................................................................
Pattern Definitions..........................................................................
PRBS Patterns ...............................................................................
Word Patterns ................................................................................
Selecting an Active Pattern...................................................................
Selecting PRBS Patterns .................................................................
Selecting the Current Word Pattern..................................................
Selecting (Recalling) a Saved Word Pattern.....................................
3-1
3-1
3-1
3-1
3-1
3-1
3-2
3-2
3-2
3-2
3-2
3-3
3-3
3-3
3-3
3-4
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Table of Contents
Word Patterns ......................................................................................
Basics............................................................................................
Creating Word Patterns using front panel controls.............................
Creating Word Patterns using menus................................................
Creating Word Patterns using remote control....................................
Saving Word Patterns .....................................................................
Recalling Word Patterns .................................................................
Generator Functions .......................................................................................
Clock Source and Frequency.................................................................
External Clock Input.............................................................................
Clock Source........................................................................................
Step Size and Frequency.......................................................................
Saving a Frequency..............................................................................
Recalling a Frequency...........................................................................
Data and Clock Outputs ........................................................................
Amplitude and Baseline Offset..............................................................
Logically Inverting Output Data (D-INV) ..............................................
Single-Ended or Differential Operation .................................................
Pattern SYNC (PYNC) and CLOCK/4 Outputs ......................................
Error Injection......................................................................................
Selection an Error Inject Mode ..............................................................
Error INJECT Input..............................................................................
Analyzer Functions .........................................................................................
Automatic Setup Functions (SYNC)......................................................
AUTO SEARCH with PRBS Patterns....................................................
AUTO SEARCH with "Non-PRBS" Patterns .........................................
How to DISABLE Automatic Pattern Resynchonization..........................
Relationship between AUTO SEARCH and DISABLE...........................
Synchronization (LOCK) Threshold.......................................................
Clock, Data, and Reference Data Inputs.................................................
Input Data Delay..................................................................................
Input Termination.................................................................................
Input Decision Threshold ......................................................................
Logically Inverting Input Data...............................................................
3-5
3-5
3-5
3-7
3-8
3-9
3-9
3-10
3-10
3-10
3-10
3-10
3-11
3-11
3-12
3-14
3-15
3-16
3-16
3-17
3-17
3-18
3-19
3-19
3-20
3-21
3-21
3-21
3-22
3-23
3-24
3-25
3-26
3-26
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Table of Contents
Single-Ended or Differential Operation ..................................................
3-27
3-27
3-28
3-29
3-33
3-33
3-33
3-34
3-35
3-36
3-37
3-42
3-44
3-45
3-45
3-45
3-46
Selecting the Reference Data Mode .......................................................
Monitor Outputs...................................................................................
Error Detection Set-up ..........................................................................
Display Mode: Totalize, Window or Test...............................................
Clearing Results and Starting Tests........................................................
Totalize Process Setup..........................................................................
Window Process Setup..........................................................................
Test Process Setup................................................................................
Viewing Results ...................................................................................
Printing Results (Reports) .....................................................................
Result Definitions .................................................................................
Error History Indicators ........................................................................
CLEAR Control....................................................................................
Audio (Beeper) Function.......................................................................
Analyzer Error Messages......................................................................
Starting & Stopping Measurements........................................................
Menus .............................................................................................................
Functions Performed using the Menu System.........................................
Menu and Function "Pages"..................................................................
General Rules for using the Menu System..............................................
Menu Summaries..................................................................................
Menu Function Definitions....................................................................
Word Edit (EDIT) ..........................................................................
Word Length (LENGTH)................................................................
Word Fill (FILL) ............................................................................
Word Order (ORDER)....................................................................
Word Synchronization Threshold (SYNC) .......................................
Buffer............................................................................................
Auto ..............................................................................................
Test Length (LENGTH)..................................................................
Test Mode (MODE) .......................................................................
Test Reports (REPORT) .................................................................
Test Threshold (THRES).................................................................
Test Squelch (SQUEL)...................................................................
3-48
3-48
3-48
3-51
3-52
3-55
3-56
3-57
3-58
3-59
3-60
3-61
3-62
3-63
3-64
3-65
3-66
3-67
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Table of Contents
Test Print (PRINT).........................................................................
Test View Previous (VIEW-PRE)....................................................
Test View Current (VIEW-CUR) ....................................................
Window Mode (MODE).................................................................
Window Interval in Bits (BITS).......................................................
Window Interval in Hrs:Min:Sec (SECOND)...................................
Window Reports (REPORT)...........................................................
RS-232 Baud Rate (BAUD)............................................................
RS-232 Parity (PARITY)................................................................
RS-232 Data Bits (SIZE) ................................................................
RS-232 End-of-Line Char.(EOL).....................................................
RS-232 Xon/Xoff (XON/XOFF)......................................................
RS-232 Echo (ECHO) ....................................................................
GPIB.............................................................................................
Utility Option (OPTION)................................................................
Utility Version (VER).....................................................................
Time Option (DATE)......................................................................
Time Option (TIME).......................................................................
3-68
3-69
3-70
3-71
3-72
3-73
3-74
3-75
3-76
3-77
3-78
3-79
3-80
3-81
3-82
3-83
3-84
3-85
Appendices
Specifications ..................................................................................................
BERT Primer/ Technical Articles...................................................................
Remote Commands .........................................................................................
Using GPIB, RS-232 .......................................................................................
Customer Acceptance Test .............................................................................
Default Settings ..............................................................................................
Cleaning Instructions .....................................................................................
Pattern Editing Software ................................................................................
Theory of Operation.......................................................................................
Glossary..........................................................................................................
Index ..............................................................................................................
A-1
B-1
C-1
D-1
E-1
F-1
G-1
H-1
I-1
Glossary-1
Index-1
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Table of Contents
List of Figures
2-1 Example of BERT Application........................................................
2-2
2-3
2-4
2-5
2-6
2-7
2-28
2-28
2-2 Nominal Generator NRZ Data and Clock Output Waveforms ...........
2-3 & 2-4 Generator (TX) Front & Rear Panels .....................................
2-5 & 2-6 Analyzer (RX) Front & Rear Panels .......................................
2-7 Generator Display..........................................................................
2-8 Analyzer Display...........................................................................
2-9 Transmitter Burst Mode Operation..................................................
2-10 Receiver Burst Mode Operation ....................................................
3-1 Nominal Generator Clock, Data Waveforms showing Amplitude,
Baseline Offset and Vtop................................................................
3-13
3-17
3-22
3-30
3-31
3-32
3-2 Generator Clock and Data Output Equivalent Circuits......................
3-3 Analyzer Clock and Data Input Equivalent Circuits..........................
3-4 TOTALIZE Measurement Process..................................................
3-5 WINDOW Measurements Process..................................................
3-6 TEST Measurement Process...........................................................
B-1 Three-stage PRBS generator ..........................................................
B-2 Four-stage PRBS generator............................................................
B-3 Seven-stage PRBS generator..........................................................
B-5
B-5
B-6
I-1 Block Diagram - GB1400 TX..........................................................
I-2 Block Diagram - GB1400 RX..........................................................
I-5
I-6
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Table of Contents
List of Tables
2-1 Generator Inputs & Outputs............................................................
2-16
2-2 Analyzer Inputs & Outputs.............................................................
2-17
3-1 PRBS (2N-1) Test Patterns.............................................................
3-2 Output Setup Rules vs. Termination Impedance...............................
3-3 Data Inhibit Logic ..........................................................................
3-4 Actions taken by Analyzer when Synchronization is Lost.................
3-5 Synchronization Threshold .............................................................
3-6 How F2, F3 determine Input Set-up ................................................
3-7 Input Terminations for CLOCK, DATA, and REF DATA................
3-8 Input Threshold Range as a Function of Termination........................
3-9 How to Tell which Display Mode is Active......................................
3-10 Menu Descriptions .......................................................................
3-11 Analyzer Menu System Overview.................................................
3-12 Generator Menu System Overview................................................
3-3
3-14
3-18
3-20
3-22
3-24
3-25
3-26
3-37
3-52
3-53
3-54
B-1 PRBS Polynomials and Shift Register feedback taps for PB200........
B-2 PRBS Polynomials, Shift Register feedback taps, GB700/ GB1400 ..
B-4
B-4
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Safety
Safety Terms Used in This User's Guide
C A U T I O N !
Indicates an operation or practice that could harm the
instrument.
W A R N I N G !
Indicates an operation or practice that could result in
personal injury or loss of life.
Safety Labels Found on the Instrument
ATTENTION
Refer to Manual
Protective Ground
(Earth) Terminal
DANGER
High Voltage
AC Power
The instrument is designed to operate from a power source that provides no more
than 250 volts RMS between the two supply conductors or between either supply
conductor and ground.
Ground the Instrument
The GB1400 is grounded through its AC power cord. Plug this power cord only
into a properly grounded, three-conductor outlet. If you operate the instrument
without a proper ground then all metal surfaces on the instrument become
potential shock hazards.
To avoid potential hazards, use this product only as specified.
Use the Proper Fuse
Operating the instrument with an improper fuse creates a fire hazard. The correct
fuses to install in the GB1400 are shown below:
Power Voltage
115 VAC
Fuse Type
5A, Slo-Blo
5A, Slo-Blo
230 VAC
Do Not Operate in Explosive Atmospheres
This instrument does not provide protection from static discharges or arcing
components and therefore must not be operated in an explosive atmosphere.
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Table of Contents
Do Not Remove Instrument Covers
To avoid a shock hazard and to maintain proper air flow, never operate the
GB1400 with any of its outside covers removed.
Static Sensitive Device Notice
GB1400 outputs use a GaAs FET design and therefore are susceptible to damage
from externally applied over-voltage or electrostatic discharge. Never apply
reverse voltage to DATA or CLOCK outputs or voltages that are outside the
range specified in Appendix A of this manual. Operate the instrument only in a
static-controlled environment.
SMA Connectors
Be careful when attaching test cables to SMA connectors. Always tighten the nut
on the SMA connector rather than the cable itself. Never tighten an SMA
connector nut using more than 10 lb.-in. of torque.
Behavior of Outputs - Turning Power On or Off
When the GB1400 Generator is powered or de-powered its DATA and CLOCK
outputs may saturate to their specified positive or negative rail, that is +2 V or - 2
V, for up to 400 milliseconds. If this condition could be harmful to your
equipment, then remove all connections to your GB1400 Generator CLOCK and
DATA outputs before powering or de-powering the instrument.
Unit Mounting
The GB1400 is designed to be placed: (1) flat on a level surface, capable of
supporting its weight, or (2) angled from the surface with the rotating carrying
handle. To change the handle's orientation, press both handle-locking buttons
(located at the hubs of the handle), rotate the handle to the desired angle, and
release the buttons. The handle will click into a locked position. Assure that the
handle is locked before placing the unit on a work surface. A Rack mounting
option is available for installation of the unit into a 19" rackmount. The rack
height for the GB1400 is 7 inches (four RMU).
Unit Cooling
The rear panel fan openings and top-mounted ventilation slots must be kept clear
for proper cooling of the unit. Allow a minimum of two (2) inches of rear panel
clearance, and one (1) inch of top clearance, while operating the unit.
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Preface
This manual describes how to use the Tektronix GB1400 Test Set. The product is
also known by the name, gigaBERT1400. This manual is your primary source of
information on how to use the GB1400 functions.
How This Manual is Organized
This manual is divided into four sections: Getting Started, Operating Basics,
Reference, and Appendices.
Getting Started provides an overview of the GB1400 and describes first time
operation.
Operating Basics describes the hardware controls, indicators, connectors, and
display elements for Tx, Rx and the cabling required. There is also a tutorial and
an application note in this section.
Reference describes the LCD Menus and Screens.
The Appendices provide a listing of specifications, a BERT technology primer,
Theory of Operation, Remote Commands, default factory settings, an extensive
Customer Acceptance Test and other useful information.
Conventions
This manual uses the following conventions:
·
·
·
The names of front-panel controls and menus appear in all upper case letters,
for example, TRANSMIT and HELP.
Names appear in the same case in this manual as they appear on the display
screens of the GB1400.
Within a procedure, a specific button to be pressed or a parameter to be
selected appears in boldface print.
Some procedures require several iterations of highlighting parameters and
selecting choices. Some procedures may require more than one menu button or
menu page selection as well.
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Preface
Related Manuals
The following document is also complementary to the GB1400:
·
The GB700 BER Tester User Manual (Tektronix part number
070-9393-02) describes how to operate the GB700 test set.
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Preface
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Getting Started
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Getting Started
GB1400 Pattern Generator and Error Detector
Features
·
·
·
Test digital data transmission up to 1400 Mb/s
Set Data Rate with 1 kHz resolution
Vary Clock and Data timing with 5 pS
resolution
·
Phase-Synchronous Clock and Data Edge
Tracking
·
·
1-Mbit data pattern memory
Measure Eye-Width at Specific BER
Automatically
·
·
Auto-Synchronization Rx/Tx Lock-up
Front panel or computer control operation
The GB1400 is a general-purpose 1400 Mb/s bit error rate tester (BERT) built to
meet the exacting standards of design engineers who need to verify and
characterize high-speed serial data transmission circuits, interfaces and systems.
While primarily a lab instrument, the GB1400’s compact design, full computer
programmability and relatively light weight also enable it to serve in
manufacturing ATE and field test applications.
The quality of a digital link depends on many factors, but everything comes
down to the issue of whether the circuit exhibits a satisfactory BER (bit error
rate) and has sufficient margin to function under stress conditions.
The GB1400 has all of the features you expect in a general-purpose BERT, and
some you expect only in more expensive instruments, such as automated eye-
width measurements at a specified BER, and the ability to accept an external
real-time data stream for bit error testing. Also, the GB1400 has options to add
advanced features, such as Burst Mode (which also extends external clock range
down to 150 kb/s), and a 1-Mbit programmable pattern memory option.
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Getting Started
Symmetrical, Low-Jitter Output Waveforms
The GB1400 generates low-jitter, symmetrical waveforms over its entire
operating frequency range. The clock and data ports provide both true and
inverted output signals. The instrument can drive single-ended or differential
ECL inputs.
Applications
The GB1400 is focused on the research, design, and manufacturing of
telecommunication components, modules, or links operating at data rates to
1400 Mb/s. It is frequently employed in testing and development well under this
top speed rating, where sharp clock and data waveforms are especially desired, or
where additional frequency range is thought to be needed in the future.
Sample Applications
·
·
·
·
·
·
·
·
·
·
·
Development of Gigabit LAN/Data Comm Devices:
High-Speed Fibre Channel, Ethernet
Digital Video (MPEG, SDV, HDDV)
Wideband Satellite Data Links
SONET/SDH Network Devices up to OC-12e/STM4e
High-speed GaAs/ECL/E/O device testing
Test Clock Recovery Circuits
Parallel-to-Serial Analysis with Tektronix MB100
Testing of High Speed Fibre Channel links up to 1,063 Mb/s
Gigabit Ethernet at 1,250 Mb/s.
Testing of high-speed Optical Busses (Opto Bus, Opto Bahn) at 800 Mb/s per
channel.
·
·
Satellite system testing and TDMA (Burst Mode) at 400, 800 Mb/s
GaAs, ECL and optical component testing
PRBS Or User-Defined Test Patterns
The GB1400 can generate pseudo-random bit sequences (PRBS) up to 223-1 bits
and others up to 1-Mbit in length, via user-programmable patterns. Patterns can
be created locally using setup menus or externally by using a workstation or PC.
A PC Windows-based MLPE Pattern Editor software package comes with the
1-Mbit Memory Option. Externally created patterns can be downloaded via the
GPIB or RS-232 port. All user patterns are saved in battery-backed RAM.
1-2
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Getting Started
Adjustable Inputs For Maximum Flexibility
The clock and data ports on the GB1400 Error Detector accept both true and
inverted inputs. Single-ended or differential signals can be internally terminated.
Input data delay is adjustable over a 4 ns range to accommodate different clock
and data signal path delays.
Auto Search For Easy Setup
Auto search greatly simplifies the Error Detector setup. The GB1400 Error
Detector automatically synchronizes to the incoming signal by 1) Setting the
input data decision voltage to its optimum value; 2) Adjusting input data delay
for an optimum clock/data phase relationship; 3) Selecting the correct PRBS test
pattern; and 4) selecting the correct pattern polarity (normal or inverted).
It synchronizes with any pattern sourced by a gigaBERT Pattern Generator. It
can perform a bit-by-bit comparison of an external data stream via the Reference
Data input. Thus the GB1400 can perform bit error analysis on any data pattern
with a known good reference pattern.
Powerful Analysis And Reporting Functions
The GB1400 performs a full-rate, bit-by-bit analysis of the received signal. Bit
error results are then used to calculate three bit error rate (BER) measures. Total
BER is calculated from the last power-on or reset. Window BER is calculated
over a sliding window specified in terms of time (1 second to 24 hours) or bits
(18- to 116-bits). Test BER is calculated from the start of the current test. A hard
copy of all test results can be generated locally by connecting a printer to the
parallel printer port or GPIB or RS-232 port. Reports may be printed when an
error is detected, at the end of test intervals, or both.
Front Panel Or Automated Operation
The GB1400 provides easy operation augmented by set-up store and recall.
Clear, concise LCD displays of setup and results make it easy to use. The 1
Megabit memory option for both the Pattern Generator and the Error Detector is
sufficient for storing and outputting complex data such as SONET frames, ATM
cells, MPEG digital video, etc, allowing designers to simulate “live” traffic. The
GB1400 Pattern Generator and Error Detector can be controlled via the GPIB or
RS-232 interface ports. The gigaBERT remote command set includes commands
for all setup menus and front panel selections. The status of front panel indicators
and test results can be remotely accessed.
Burst Mode
BURST mode, allows for operation with non-continuous external clocks. Use of
BURST mode requires ECL-level signals with a minimum rate during the burst
of 150 kHz. This is an option to the GB1400. See a write-up on Burst Mode at
the end of the Functional Overview section of Chapter 2.
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Getting Started
Ordering Information
gigaBERT GB1400
1400 Mb/s BERT Generator and Detector. Not available in Europe.
Includes: Power Cord, Manual.
Opt. 02 - 75 Ohm Both Sets.
Opt. 05 - BURST Mode Both Sets.
Opt. 07 - Positive ECL (Pattern Generator Only).
Opt. 08 - 1-Mbit RAM WORD Both Sets & PC Pattern Editor Software.
Opt. 2M - Rack Mounts - 2 rackmount kits
Opt. A3 - Australian 240 V, 50 Hz.
gB1400T
1400 Mb/s BERT Pattern Generator.
Opt. 02 - 75 Ohm Pattern Generator Only.
Opt. 05 - BURST Mode Pattern Generator Only.
Opt. 07 - Positive ECL Pattern Generator Only
Opt. 08 - 1-Mbit RAM WORD, Generator Only, w/ PC Pattern Edit software
Opt. 1M - Rack Mount.
Opt. A3 - Australian 240 V, 50 Hz.
gB1400R
1400 Mb/s BERT Error Detector.
Opt. 02 - 75 Ohm Error Detector Only.
Opt. 05 - BURST Mode Error Detector Only.
Opt. 08 - 1-Mbit RAM WORD, Detector Only w/ PC Pattern Edit Software
Opt. 1M - Rack Mount.
Opt. A3 - Australian 240 V, 50 Hz
1-4
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Getting Started
GB Comparison
Feature
GB660/CSA907A GB700
GB1400
Tx and Rx
Tx and Rx
Tx and Rx
Transmitter
Frequency range
Internal Clock Source
External Clock
150 kHz to 700 MHz 150 kHz to 705 MHz
150 kHz to 700 MHz 150 kHz to 705 MHz
1 MHz to 1405 MHz
1 MHz to 1405 MHz
150 kHz to 1405 MHz
1 kHz (was 10 kHz)
External Clock w/Burst Mode1 150 kHz to 700 MHz 150 kHz to 705 MHz
Freq Resolution CR/LF
(Internal Clock)
Clock /Data
Output Amplitude
Clock/Data
1 kHz
1 kHz
500mV to 2.0 V
-2.0V to +1.8 V
500mV to 2.0 V
-2.0V to +1.8 V
500mV to 2.0 V
-2.0V to +1.0 V
-2.0V to +1.8 V with
PECL opt.
Output Offset
Clock/Data Threshold
Resolution
50 mV steps
50 mV steps
50 mV steps
Std. Programmable Memory
16 bits
128 Kbits
16 bits
Optional Memory
128 Kbits
7,15,17,20,23
Standard Feature
none
7,15,17,20,23
Standard Feature
1 Mbit
7,15,17,20,23
Optional Feature
PRBS Patterns (2n-1)
Burst Mode New Line
(External Clk Only)
Receiver
Frequency range
150 kHz to 705 MHz 150 kHz to 705 MHz
150 kHz to 705 MHz 150 kHz to 705 MHz
1 MHz to 1405 MHz
150 kHz to 1405 MHz
Optional Feature
w/Burst Mode1
Burst Mode (Ext Clk Only)
Standard Feature
Standard Feature
Clock/Data Input levels (max)
Clock Input Threshold
Data Input Threshold
Clock/Data Threshold
Resolution
500 mV to 6.0 V p-p 500 mV to 6.0 V p-p
500 mV to 2.0 V p-p
Fixed threshold levels
-1.5V to 1.0 V
-3.00 to +4.5 V
-3.00 to +4.5 V
50 mV steps
-3.00 to +4.5 V
-3.00 to +4.5 V
50 mV steps
50 mV steps
Clock/Data Input Terminations
Single-Ended operation
GND, AC, -2V, +3V
Automatic selection
GND, AC, -2V, +3V
Automatic selection
GND, AC, -2V
Requires external
cable2
Clk/Data Delay Range /
Resolution
±4 ns in 100 pS
steps
±4 ns in 20 pS steps
±4 ns in 5 pS steps
Note 1 Burst mode operation requires ECL levels and is DC coupled
Note 2 Single-ended operation requires ext. cable connection from rear panel DATA THRESHOLD SMA
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Getting Started
GB1400 Instrument Configurations - Standard and Burst Option
GB1400 instruments are sold with and without the BURST option. To determine if the burst option is
installed in a GB1400, press the F1 key several times until you get to the UTIL menu. Then select the
OPTION menu. The OPTIONS menu will tell you if the Burst option is installed in the unit. External
indications of the BURST option are unique labels for both transmitter and receiver. See a write-up on
Burst Mode at the end of the Functional Overview section of Chapter 2.
GB1400 with no Burst Option Standard instrument configuration
All standard configuration GB1400 Generators (no burst option) have an AC coupled external clock
input. All standard configuration GB1400 Analyzers (no burst option) have AC coupled paths in the
receiver clock input circuitry.
GB1400 with Burst Option
When the BURST option is installed in the GB1400, the AC coupled paths in both transmitter and
receiver are eliminated. This will also change several specifications listed in the table below. External
clock inputs to the GB1400 transmitter must be ECL levels when the BURST option is installed. Clock
inputs into the GB1400 receiver must be ECL levels and are terminated into 50 Ohms to -2V.
GB1400 Clock Signals for Standard and Burst and Instruments
Standard Coupling
Burst (Option) Coupling
GB1400 TX
External Clock Input
50 Ohm, AC coupled,
2V max
50 Ohm to -2V, DC coupled,
ECL levels
GB1400 RX
Clock Input
50 Ohm, AC coupled,
2.0V max
50 Ohm to -2V, DC coupled,
ECL levels
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Getting Started
Initial Self-Check Procedure
You may perform the following procedure as an initial self-check of your
GB1400 Generator and Analyzer. It is also a useful introduction to the basic
features and operation of the GB1400.
The fan openings of the GB1400 needs 2-inches of clearance for proper
ventilation.
Procedure
1.
2.
Make sure both the Generator and Analyzer are equipped with the proper
fuse.
Make sure that the Generator and Analyzer rear-panel power switches
are ON, and that their front-panel power switches are in the STBY
position.
3.
4.
Plug both instruments into grounded (three-conductor) AC power outlets.
Connect a 50-Ohm SMA cable from the Generator CLOCK output to the
Analyzer CLOCK input. If using 75-Ohm option, use &5 OHM
SMA/BNC cable.
5.
6.
Connect a 50-Ohm SMA cable from the Generator DATA output to the
Analyzer DATA input.
Connect a 50-Ohm SMA cable from the Analyzer rear panel DATA
THRESHOLD output to the Analyzer DATA BAR input (required for
single-ended data inputs).
7.
8.
Power the Generator while pressing and holding its VIEW ANGLE,
MSB 1 and (PATTERN) CLEAR keys simultaneously. Release the key
after the message Default Settings appears in the display. Repeat this
procedure with the Analyzer. This will force both the Generator and
Analyzer to power up using factory default settings.
Set up the Generator clock and data outputs using controls in the
OUTPUT box as follows:
Set this parameter…
to this value
… using this procedure.
DATA amplitude.
2 volts
Press the DATA key.
Press AMPLITUDE up/down keys until
data amplitude is set to 2.00V.
Press BASELINE OFFSET up/down keys
until data baseline offset is set to -1.00V.
DATA baseline offset
CLOCK amplitude
-1 volt
2 volts
Press CLOCK.
Press AMPLITUDE up/down keys until
clock amplitude is set to 2.00V.
CLOCK baseline offset
-1 volt
Press BASELINE OFFSET up/down keys
until clock baseline OFFSET is set to
-1.00V.
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Getting Started
23
9.
Set Generator pattern to a 2 -1 bit PRBS using controls in the
PATTERN box as follows:
a.
b.
Press PRBS.
Press the pattern up/down keys until PATTERN is set to PN 23.
10.
11.
Verify that the Generator error injection rate is off. If the LED in the
error inject RATE key is on, then press RATE one or more times until it
turns off.
Verify that the Analyzer auto-search function is enabled. If the LED in
the AUTO SEARCH key is off, then press AUTO SEARCH one time to
turn it on. At this point, verify that the green LOCK LED in the
Analyzer SYNC box is on.
12.
13.
14.
Zero all Analyzer error counts by pressing CLEAR in the ERROR
DETECTION group.
Reset all Analyzer history LEDs by pressing CLEAR in the ERROR
HISTORY group.
Verify GB1400 Analyzer can detect errors by pressing the Generator
error inject SINGLE key several times. Verify that the Number of Errors
count displayed by the Analyzer increments each time the Generator
SINGLE key is pressed.
In effect you are now performing a bit error rate test on the test cables connecting
the GB1400 Generator and Analyzer. In an actual BER test, GB1400 Generator
clock and data outputs would be connected to inputs on a "device under test"
(DUT) while GB1400 Analyzer inputs would be connected to outputs on the
DUT.
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Operating Basics
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Functional Overview
This section describes how to use and navigate through the basic functions of the
GB1400, including:
·
·
·
·
BERT Basics
Controls, indicators and connectors
Display Formats
Outputs and Inputs
Also in this section is:
·
Tutorial - "Understand GB1400 instrument setup for BER testing using
PRBS patterns";
·
·
Application Note - Auto Search Synchronization with GB1400; and,
Application Example - GB700/ GB1400 Optical component test.
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Functional Overview
BERT Basics - GB1400
The GB1400 Generator and Analyzer together comprise a 1400 Mb/s, serial, bit
error rate test system or BERT.
A BERT is an instrument designed to measure the bit error rate (BER)—or more
generally, the error performance—of a digital communications device, module, or
system.
A typical BERT application, for example, would be to measure the error
performance of the electrical-to-optical (E/O) and optical-to-electrical (O/E)
output modules of a high-speed fiber optic transmission system (FOTS), as
shown in the figure below.
GB1400 Generator
GB1400 Analyzer
CLOCK DATA
CLOCK DATA
IN
IN
OUT
OUT
O/E
E/O
Figure 2-1. Example, BERT Application
The GB1400 is described as a serial BERT because it is designed to test one
digital path at a time. The term serial also distinguishes the GB1400 from
parallel BERTs, such as the Tektronix MB100, which is designed to test multiple
digital signal paths simultaneously.
The GB1400 Generator, also known as the transmitter or "Tx", can generate
various test patterns, including pseudo-random bit sequences (PRBS) and user-
defined word patterns. The Generator output consists of a two level, non-return to
zero (NRZ) data signal and its associated clock signal, as illustrated in Figure
2-2. In the NRZ format, the data signal remains at either a logic "1" or logic "0"
level for the entire duration of each bit time slot, except for a small transition
period between time slots containing different data. The corresponding clock
signal is a nominal "square wave" whose frequency defines the bit rate of the test
signal.
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Functional Overview
Falling edge of CLOCK
in middle of DATA "eye"
Rising edge of CLOCK Coin-
cident with DATA transitions
CLOCK
DATA
Figure 2-2. Nominal Generator NRZ Data and Clock Output
Waveforms
The nominal Generator clock/data phase relationship is fixed so that the falling
edges of the clock signal occur in the middle of bit time slots of the data signal.
The amplitude and baseline offset of the Generator's clock and data outputs are
adjustable to insure compatibility with a wide range of input circuit designs and
logic families including ECL, positive ECL, and GaAs.
The GB1400 Analyzer, also known as the receiver or "Rx", can terminate and
analyze the NRZ output of a digital device, module, or system being tested by the
GB1400 Generator or an equivalent signal source. The decision voltage or
threshold of the Analyzer DATA and CLOCK inputs can be adjusted to
accommodate different logic families. The Analyzer can also add a variable
amount of delay to the input data signal to accommodate different clock/data
phase relationships at the output of the device under test.
The primary measurements made by the GB1400 Analyzer are bit errors and bit
error rate.
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Functional Overview
Controls, Indicators and Connectors
The first four figures in this section identify the controls, indicators and
connectors located on the front and rear panels of the GB1400 Generator (Tx)
and GB1400 Analyzer (RX).
gigaBERT1400 GENERATOR
FREQUENCY (kHz)
PATTERN
OUTPUT
ERROR INJECT
RATE SINGLE
AMPL
VIEW
OFFSET
ANGLE
MEMORY
PANEL
LOCK
PATTERN
OUTPUT
CLOCK DATA
CLOCK
WORD
PRBS
FREQUENCY
F1
F2
F3
F4
CLEAR SET
LENGTH
GPIB
OFFSET
AMPLITUDE
ADDR
STEP
WORD
BIT
3
INVERT
DATA
(D-INV)
LOCAL
MSB
1
RECALL SAVE
RECALL SAVE
2
4
5
6
7
8
REMOTE
EXT
OUTPUT
CLOCK
ON
OFF
INPUT
CLOCK
DATA
PATTERN SYNC
CLOCK/4
DATA
(2)
(1)
50 Ohm 2 V Max
50 Ohm SOURCE
50 Ohm SOURCE
POWER
(1) With Option 2, these outputs are 75 Ohm.
(2) With Option 5, the input is ECL levels only.
Figure 2-3. Front Panel, GB1400 Generator (Tx)
RS-232C
GPIB
PHASE A
PHASE B CLOCK/2 ERROR INJECT DATA INHIBIT
WARNING
ELECTRICAL SHOCK HAZARD
THIS INSTRUMENT MUST BE GROUNDED
DO NOT OPEN INSTRUMENT REFER SERVICING TO
QUALIFIED PERSONNEL
AC-LINE
DISCONNECT POWER CORD BEFORE REPLACING
FUSE
FOR CONTINUED FIRE PRODUCTION REPLACE ONLY
WITH SPECIFIED FUSES
INPUT
MAX
LINE
VOLTAGE
RANGE
90-132V
180-250V
POWER FUSE
115
230
175W
175W
5A SLOBLO
5A SLOBLO
AUTO SELECT
FREQUENCY 47-63 Hz
Figure 2-4. Rear Panel, GB1400 Generator (Tx)
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Functional Overview
gigaBERT 1400 ANALYZER
FREQUENCY (kHz)
ERROR RATE
TOTALIZE
ERROR HISTORY
SYNC LOSS
CLEAR
BIT
PHASE
POWER
VIEW
ANGLE
DELAY/
MEMORY
PANEL
LOCK
PATTERN
ERROR DETECTION
DISPLAY
INPUT
DELAY
WORD
LENGTH
F1
F2
F3
F4
5
CLEAR SET
PRBS
WORD
SYNC
CLEAR
GPIB
CLK REF
LOCK
ADDR
AUDIO
VOL
RATE
AUTO
SEARCH
BIT
MSB
1
2
3
4
6
7
8
LOCAL
V-TERM V-THRESH
RECALL SAVE
DISABLE
REMOTE
D-INV
EXT
MONITOR
CLOCK
ON
OFF
DATA
DATA
REFERENCE DATA
CLOCK
PATTERN
SYNC
DATA
CLOCK
(1)
(1)(2)
50 Ohm, 2V MAX
50 Ohm, 1.5V MAX
50 Ohm SOURCE
POWER
(1) With Option 2, this input is 75 Ohm.
(2) With Option 5, the input is ECL levels only.
Figure 2-5. Front Panel, GB1400 Analyzer (RX)
DATA
THRESHOLD
ERROR INHIBIT RZ ERROR
OUTPUT
RS-232C
GPIB
PRINTER
WARNING
ELECTRICAL SHOCK HAZARD
THIS INSTRUMENT MUST BE GROUNDED
DO NOT OPEN INSTRUMENT REFER SERVICING TO
QUALIFIED PERSONNEL
AC-LINE
DISCONNECT POWER CORD BEFORE REPLACING
FUSE
FOR CONTINUED FIRE PRODUCTION REPLACE ONLY
WITH SPECIFIED FUSES
INPUT
MAX
LINE
VOLTAGE
RANGE
90-132V
180-250V
POWER FUSE
115
230
175W
175W
5A SLOBLO
5A SLOBLO
AUTO SELECT
FREQUENCY 47-63 Hz
Figure 2-6. Rear Panel, GB1400 Analyzer (RX)
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Functional Overview
Display Formats
The normal display format for the Generator and Analyzer are explained below.
Note that the "normal" format is simply the format of the display when not in the
menu mode.
Generator (Tx) Display
The Generator has a two-line by 24-character high-contrast liquid crystal display
(LCD). The Generator display in its normal (non-menu) mode is illustrated in the
figure below.
Frequency (kHz)
Pattern
Output
AMPL
OFFS
1405000
PN23
2.00 V
-1.00 V
FREQ 0
ERR OFF
Memory
Figure 2-7. Generator Display in Its Normal (Non-menu) Mode
The function of each field in the normal Generator display format—that is the
format used when the Generator is not in the menu mode - is described below:
·
The top left section of the Generator display is used to show the current
frequency of the internal clock in MHz. For example a display of
6 2 2 . 0 5 0 indicates a frequency of 622.050 MHz.
·
·
The top middle section normally shows the current test pattern. For example
23
PN23 INVindicates that the current pattern is an inverted 2 -1 PRBS.
The top right section of the display shows the amplitude of the CLOCK or
DATA output, depending on which output control (CLOCK or DATA) is
selected.
·
The bottom leftsection of the Generator display may show either the
presently selected word memory (WORD 0 ... WORD 7) or the selected
frequency memory (FREQ 0 ... FREQ 9).
·
·
The bottom middle section of the display shows the currently selected
Generator error inject mode.
The bottom right section of the Generator display will normally show the
baseline offset of the CLOCK or DATA output, depending on which output
control (CLOCK or DATA) is selected.
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Functional Overview
Analyzer (RX) Display
Like the Generator, the Analyzer has a two-line by 24-character high-contrast
liquid crystal display (LCD).The Analyzer display in its normal (non-menu)
mode is illustrated in the figure below.
Frequency (kHz)
Error Rate
5.0E-06
PN23
Totalize
1405000
2410538
-0.05 V
1.2 ns
Delay/ Memory
Figure 2-8. Analyzer Display in Its Normal (Non-menu) Mode
Like the Generator, the Analyzer has a two-line by 24-character high-contrast
liquid crystal display (LCD). The function of each field in the normal Analyzer
display format -that is the format used when the Analyzer is not in the menu
mode -is described below:
·
The top left section of the Analyzer display is used to show the measured
frequency of the input clock signal in MHz. For example a display of
6 2 2 . 0 5 indicates a measured frequency of 622.05 MHz. Note that the
Analyzer frequency display contains five significant digits while the
Generator frequency display contains six. This is because the frequency
shown in the Analyzer display is a measurementresult while the frequency
shown in the Generator display is an instrumentsetup which is known with
more precision.
·
The top middle and top right sections of the display normally show measured
bit error rate and bit errors respectively. BER is expressed in exponential or
"E" notation. For example, a display of 1.5E-09 indicates a measured BER
-9
of 1.5 x 10 . The Analyzer calculates BER and counts bit errors in three
modes simultaneously: Window, Test, and Totalize. The symbol in front of
the BER field indicates which mode has been selected for display. Window
results are preceded by a blank space, that is no symbol. Totalize results will
be preceded by an ¥ (infinity) symbol. Test results will be preceded by a T,
U, or R depending on the selected test mode: timed, untimed, or repeat.
Refer to Chapter 4 for more information on displaying Analyzer results and
starting and stopping tests.
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Functional Overview
·
The bottom leftsection of the Analyzer display can show the following setup
parameters: delay in nanoseconds for the DATA or REF DATA input; the
selected input termination (GND, -2V, or AC) for the CLOCK, DATA, or
REFERENCE DATA input, or the selected word memory (WORD 0 ...
WORD 7), Note that DATA input delay may be set manually by the user, or
automatically by the AUTO SEARCH feature.
To control the delay, termination or threshold settings for the DATA input,
make sure F2 and F3 LEDs are turned OFF.
Pressing F2 places the unit into CLOCK control (F2 LED illuminated). The
V-TERM key is redefined to allow control of the Input CLOCK Termination
voltage. The status of each key LED and LCD displayed value now reflects
the CLOCK Input signal.
Pressing F3 places the unit into REF Data control mode (F3 LED
illuminated). The Delay, V-TERM and V-THRS keys are redefined to allow
control of the Input REF DATA Delay, Termination Volga and Threshold.
The status of each key LED and LCD displayed value now reflects the REF
DATA Input signal.
·
·
The bottom middle section of the display shows the currently selected
23
Analyzer pattern, for example PN23 indicates a 2 -1 PRBS. This section
will also indicate when input pattern inversion is enabled by displaying INV
after the pattern name.
The bottom right section of the Analyzer display shows the current value of
the input threshold in volts for the CLOCK, DATA, or REF DATA inputs.
Note that the CLOCK and DATA input thresholds may be set manually by
the user, or automatically by the AUTO SEARCH feature.
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Functional Overview
Outputs and Inputs
This section introduces all inputs and outputs of the GB1400 Generator and
Analyzer. Unless otherwise indicated, all signal inputs and outputs are equipped
with SMA female connectors and have a nominal input or output impedance of
50 ohms. However, a 75 Ohm Option is available for both the Generator and
Analyzer which changes nominal impedance of key inputs and outputs to 75
ohms.
Note: The same term can be expressed three different ways.
= clock bar
= NOT clock
clock
DATA
= DATA BAR = NOT DATA
The front panel of the GB1400 Tx is divided into nine sections:
LCD Display
Clock
Error Inject
Pattern
Output Controls
Power Switch
GPIB
Output Connectors
Generator OUTPUT Connectors Section
The OUTPUT connectors section of the Generator front panel contains the
outputs listed below.
OUTPUT
CLOCK
DATA
PATTERN SYNC
CLOCK/4
CLOCK
DATA
50 Ohm SOURCE
50 Ohm SOURCE
·
·
CLOCK and DATA [outputs]: These two connectors comprise the main
test signal output of the Generator. DATA is the NRZ output of the pattern
generator and CLOCK is its corresponding clock signal. The amplitude and
baseline offset of CLOCK and DATA are variable. CLOCK and DATA may
be used to drive single-ended clock and data inputs, respectively.
CLOCK-BAR and DATA-BAR [outputs]: These are complimentary
outputs to CLOCK and DATA. That is, CLOCK and CLOCK-BAR together
can drive a differential clock input, while DATA and DATA-BAR together
can drive a differential data input. These complementary outputs should be
terminated with a 50 Ohm load (or a 75 Ohm load if the 75 Ohm Option is
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Functional Overview
installed) when not in use—that is, when the Generator is driving single-
ended inputs.
·
·
CLOCK/4 [output]: This is a clock signal at one quarter the frequency of
CLOCK. This output may be useful when observing generator outputs using
an oscilloscope that does not have the bandwidth to trigger on the CLOCK
output.
PATTERN SYNC [output]: This is a pulse that occurs once per pattern
frame. This output may be useful as a trigger signal when observing the
Generator data output using an oscilloscope. The location of PATTERN
SYNC is fixed. A pulse is generated at the start of the pattern frame.
Generator CLOCK Section
Controls in the CLOCK section of the Generator are used to select clock mode
(internal or external) and to set up the instrument's internal clock. The CLOCK
section also contains the input connector for an external clock source. These
controls and input are introduced below.
FREQUENCY
STEP
RECALL
SAVE
EXT
INPUT
(2)
50 Ohm 2 V Max
·
FREQUENCY: When this key is selected (LED on), the clock up/down
keys may be used to adjust the frequency of the internal Generator clock up
or down. Each press of the frequency up or down key will increment or
decrement frequency by the current step size.
·
·
STEP: Select this key to adjust the frequency adjustment step size from
1 kHz to 100 MHz.
SAVE: Use this key to save the present frequency into one of 10 frequency
memory locations.
·
·
RECALL: Use this key to recall a previously saved frequency.
EXT: Press this key to toggle between internal clock mode (LED off) and
external clock mode (LED on).
·
INPUT: This is an input for an external clock source. A signal must be
provided to this input when clock mode is set to external. However, when
clock mode is internal, any signal appearing at this input will be ignored.
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Functional Overview
Generator OUTPUT Section
The controls shown below are used to set up the Generator's clock and data
outputs.
OUTPUT
CLOCK DATA
OFFSET
AMPLITUDE
INVERT
DATA
(D-INV)
·
·
·
CLOCK: Use this key to select clock amplitude and offset set up mode.
DATA: Use this key to select data amplitude and offset set up mode.
AMPLITUDE (• ,¯ ): Use these up/down keys to adjust clock or data
output amplitude.
·
·
BASELINE OFFSET (• ,¯ ): Use these up/down keys to adjust clock or
data baseline offset.
INVERT DATA: Use this key to toggle between output data inverted (LED
on) and non-inverted (LED off) mode.
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Functional Overview
Generator Rear Panel
The rear-panel of the Generator contains the auxiliary signals, remote control,
and AC-power inputs shown below. See the appendix for instruction on how to
set up the RS-232 and GPIB ports, and general information on using external
controllers with the Generator.
PHASE A
PHASE B CLOCK/2 ERROR INJECT DATA INHIBIT
·
·
PHASE A: An SMA connector provides signal output for DATA Phase A.
This phase-shifted data pattern provides signals suitable for MUX/DEMUX
testing. Phase A/B outputs are half rate data patterns (alternating bits).
PHASE B: : An SMA connector provides signal outputs for DATA Phase
B. This phase-shifted data pattern provides signals suitable for
MUX/DEMUX testing.
·
·
CLOCK/2: : An SMA connector provides signal outputs for CLOCK/2.
ERROR INJECT: An ECL signal applied to this input may be used to
control error injection when the Generator is in the external (EXT ERR)
injection mode. One error will occur for each rising edge of this signal.
·
·
·
DATA INHIBIT: An ECL signal applied to this input may be used to
asynchronously gate off the data outputs of the Generator.
RS-232C [input/output]: A two-way serial port that may be connected to
an external controller or serial printer.
GPIB [input/output]: An IEEE-488 standard I/O port that may be
connected to a GPIB compatible controller. This port is not compatible with
stand-alone GPIB printers.
·
AC LINE [power input]: This is the AC power input connector for the
Generator.
Changing the Line Fuse
1. Disconnect the AC line cord.
2. Slide the fuse cover upwards and remove the fuse.
3. Install the correct line fuse into the holder.
115 VAC
230 VAC
5A, Slo-Blo
5A, Slo-Blo
4. Close the fuse cover.
5. Plug in the line cord.
Allow at least two inches of clearance for the rear panel fan opening and at least
one inch of clearance for the top of the unit. This assures proper cooling of the
unit. Do not operate the Generator on its rear side.
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Functional Overview
Analyzer INPUT Section
The INPUT section of the Analyzer front panel contains the test signal NRZ data
and clock inputs shown below.
REFERENCE DATA
CLOCK
DATA
CLOCK
DATA
·
CLOCK and DATA [inputs]: These inputs comprise the main test signal
input to the Analyzer. DATA is the main NRZ data input to the Analyzer
pattern detector and CLOCK is its corresponding clock signal. Both inputs
have selectable input terminations. In addition, a variable amount of delay
may be added to the DATA input to properly phase-align the clock and data
signals. CLOCK and DATA may be used to terminate singled-ended clock
and data outputs, respectively.
For single-endedapplications, the DATA input threshold is programmable.
This requires an external cable connection from the rear panel DATA
THRESHOLD output to the unused DATA input. Only the unused
"DATA-BAR" input needs the threshold signal. The CLOCK input is self-
biasing for single-ended applications.
·
·
CLOCK-BAR and DATA-BAR [inputs]: These are complimentary inputs
to CLOCK and DATA. That is, CLOCK and CLOCK-BAR together
comprise a differential clock input, while DATA and DATA-BAR together
comprise a differential data input. When the Analyzer is connected to
singled-ended clock and data signals, these inputs are not used.
Note: In DIFFERENTIAL applications, the programmed threshold voltage is
not used.
REFERENCE DATA [input]: This is an input for a reference data signal.
When the external reference mode is selected (LED in EXT key is on), the
signal appearing at the REF DATA input will be used as the reference signal
to perform bit error analysis instead of a (reference) pattern generated by the
Analyzer's error detection circuit. Note that REF DATA uses the same clock
signal as DATA, however different amounts of delay can be added to the
DATA and REF DATA inputs to account for phase differences between the
two signals.
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Functional Overview
Analyzer MONITOR Section
The MONITOR section of the Analyzer front panel contains the auxiliary outputs
shown below. These outputs may be used to monitor the test signal as seen by
the Analyzer.
MONITOR
PATTERN
SYNC
DATA
CLOCK
50 Ohm SOURCE
·
·
·
CLOCK [output]: A buffered copy of the clock signal received by the
Analyzer.
DATA [output]: A regenerated (re-clocked) version of the data signal
received by the Analyzer.
PATTERN SYNC [output]: A train of pulses that occur once per pattern
frame. This output may be used to trigger an oscilloscope to view the
beginning (first bit/byte) of the data pattern.
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Functional Overview
Analyzer Rear Panel
The rear-panel of the Analyzer contains the auxiliary signal, remote control,
printer, and AC-power inputs shown below. See the appendix for instruction on
how to set up the RS-232 and GPIB ports, and general information on using
printers and external controllers with the Analyzer.
DATA
THRESHOLD
ERROR INHIBIT RZ ERROR
OUTPUT
RS-232C
GPIB
PRINTER
·
·
DATA THRESHOLD OUTPUT: The programmed DATA threshold
voltage is set via the front panel. Connect to DATA BAR input for single-
ended applications. Requires external cable connection.
ERROR INHIBIT INPUT: An ECL signal applied to this input may be
used to asynchronously gate on/off the error detection function of the
Analyzer. That is, while the signal at this input is low, errors are counted.
While it is high, error counting is inhibited.
·
·
RZ ERROR OUTPUT: This is an ECL output signal. One pulse will be
generated at this output for each bit error detected. May be connected to an
external recording device, for example, to log the exact times that errors
occur.
PRINTER [output]: A one-way port that may be connected to a "parallel
printer"—that is, any printer compatible with the parallel port (LPT1 etc.) of
an IBM-compatible PC.
·
·
RS-232-C [input/output]: A two-way serial port that may be connected to
an external controller (e.g. a PC or workstation) or to a serial printer.
GPIB [input/output]: A two-way, IEEE-488 compatible I/O port that may
be connected to an external controller via a GPIB cable.
Changing the Line Fuse
1. Disconnect the AC line cord.
2. Slide the fuse cover upwards and remove the fuse.
3. Install the correct line fuse into the holder.
115 VAC
230 VAC
5A, Slo-Blo
5A, Slo-Blo
4. Close the fuse cover.
5. Plug in the line cord.
Allow at least two inches of clearance for the rear panel fan opening and at least
one inch of clearance for the top of the unit. This assures proper cooling of the
unit. Do not operate the Analyzer on its rear side.
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Functional Overview
Connectors, Terminations, and Levels
Tables 2-1 and 2-2 below summarize the physical interface characteristics of all
GB1400 Generator and Analyzer inputs and outputs.
Table 2-1. Generator (Tx) Inputs and Outputs
Connector Label
Signal Type Location
Connector
Type
Impedance, amplitude,
and offset
DATA
output
output
output
output
OUTPUT section
SMA,
female
50 Ohm, see NOTE 1,
variable amplitude and
offset
CLOCK
OUTPUT section
OUTPUT section
OUTPUT section
SMA,
female
50 Ohm, see NOTE 1,
variable amplitude and
offset
DATA-BAR
CLOCK-BAR
SMA,
female
50 Ohm, see NOTE 1,
variable amplitude and
offset
SMA,
female
50 Ohm, see NOTE 1,
variable amplitude and
offset
CLOCK/4
output
output
input
input
input
I/O
OUTPUT section
OUTPUT section
CLOCK section
rear panel
SMA,
female
50 Ohm, 200mV into 50W
PATTERN SYNC
CLOCK INPUT
DATA INHIBIT
ERROR INJECT
RS-232
SMA,
female
50 Ohm, 200mV into 50W
SMA,
female
50 Ohm, 2V max, see
NOTE 2
BNC,
female
50 Ohm to -2V, ECL
50 Ohm to -2V, ECL
rear panel
BNC,
female
rear panel
25 pin, D
type
RS-232C standard levels
and impedance
GPIB
I/O
rear panel
GPIB
IEEE-488 standard levels
and impedance
Note 1: A 75-Ohm version of the GB1400 is an option.
Note2: BURST Mode units require ECL-level inputs and are terminated with 50-Ohms to -2V.
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Functional Overview
Table 2-2. Analyzer (RX) Inputs and Outputs
Connector Label
Signal
Type
Section
Connector
Type
Impedance, threshold, and delay
DATA/DATA BAR
Input
Input
Input
INPUT
SMA, female
SMA, female
SMA, female
50 Ohm, see NOTE 1, variable
threshold and delay. Selectable
termination: GND, -2 V, AC
CLOCK/CLOCK
BAR
INPUT
INPUT
50 Ohm, see NOTE 1, fixed
threshold. Selectable termination:
GND, -2 V, AC
REF DATA
50 Ohm, ECL, variable delay,
selectable termination GND, -2V,
AC
PATTERN SYNC
CLOCK
output
output
output
input
MONITOR
MONITOR
MONITOR
rear panel
SMA, female
SMA, female
SMA, female
BNC, female
50 Ohm, 200mV into 50W
50 Ohm, 200mV into 50W
50 Ohm, 200mV into 50W
50 Ohm, ECL
DATA
ERROR INHIBIT
INPUT
RZ ERROR
OUTPUT
output
rear panel
BNC, female
50 Ohm, 200mV into 50W
PRINTER
RS-232C
GPIB
output
I/O
rear panel
rear panel
rear panel
25-pin, D male
25-pin, D male
GPIB
Compatible with PC parallel printers
RS-232 levels and impedance
I/O
IEEE-488 standard levels and
impedance
Note 1: A 75-Ohm version of the GB1400 is an option.
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Functional Overview
Controls and Indicators
All of the controls, indicators, inputs, and outputs found on the Generator or
Analyzer front or rear panels are discussed in the following section.
Power Switches
The ON/OFF power switch is located on the left side of the test instrument below
the LCD screen. The power switch switches the 120/240 VAC to the system
power supply. When off, a Battery backup circuit powers the non-volatile RAM.
Unit Mounting
The GB1400 is designed to be placed: (1) flat on a level surface, capable of
supporting its weight, or (2) angled from the surface with the rotating carrying
handle. To change the handle's orientation, press both handle-locking buttons
(located at the hubs of the handle), rotate the handle to the desired angle, and
release the buttons. The handle will click into a locked position. Assure that the
handle is locked before placing the unit on a work surface. A Rack mounting
option is available for installation of the unit into a 19" rackmount. The rack
height for the GB1400 is 7 inches (four RMU).
Unit Cooling
The rear panel fan openings must be kept clear for proper cooling of the unit.
Allow a minimum of two (2) inches of rear panel clearance, and one (1) inch of
top clearance, while operating the unit.
View Angle and Panel Lock Keys
The PANEL LOCK and VIEW ANGLE keys are located near the top, left side of
the front panel.
·
·
VIEW ANGLE: Use this key to select the optimum LCD viewing angle.
PANEL LOCK: Use this key to "lock" and "unlock" the front panel. While
the front panel is locked, all keys that can cause setup changes are disabled.
This feature can help prevent accidental loss of data when performing long-
term or critical tests.
RESET to Factory Default
To return the Generator or Analyzer to factory default settings, turn the
instrument OFF and then re-power it while pressing and holding the VIEW
ANGLE, MSB 1, and (PATTERN) CLEAR keys at the same time. Release these
keys after the message Default Setup appears in the display.
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Functional Overview
GPIB Section Controls
There are two keys in the GPIB section:
·
·
ADDR: Key used to set GPIB address in the range 0 to 30.
LOCAL: The LED in this key indicates whether the instrument is in the
local mode (LED off) or remote mode (LED on). If the LED is on, you can
return the instrument to local mode by pressing the LOCAL key.
Note that these two keys are used only when operating the instrument via its
GPIB port. For more information on the GPIB port and remote control in general,
see the appendix. For detailed descriptions of all remote commands, see the
appendix.
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Functional Overview
Pattern Controls and Function Keys
The PATTERN section of both the Analyzer and Generator front panels contains
two basic types or groups of controls: "pattern" and "function". The four
function or "soft" keys—F1, F2, F3, and F4—have different functions depending
on the current mode of the instrument. A primary function of these controls is to
access and navigate the menu system. Pattern controls, which includes all other
controls in the PATTERN section, are used to select edit, save, and recall test
patterns.
WORD
F1
2
F2
F3
F4
5
CLEAR
SET
PRBS
LENGTH
CLK REF
WORD
RECALL
MSB
1
3
4
6
7
8
SAVE
·
·
·
PRBS: Press this key, and then the pattern up/down keys to select a PRBS
pattern.
WORD: Press this key either to select a word or ROM pattern or to edit the
current word pattern.
SAVE and RECALL: Use these keys to save and recall user-created word
patterns to and from non-volatile memory. The standard GB1400 can store
up to ten 16-bit or short word patterns. When equipped with the 1-Mbit
option, the GB1400 Generator and Analyzer can store up to ten (10) 65-kbit
patterns, depending upon the buffer size set for word memory.
·
·
·
WORD LENGTH: Press this key and then the up/down keys, to adjust the
length of the current word pattern.
(• ,¯ ): These are the pattern up/down keys. Their effect depends on which of
the above pattern keys has been selected.
MSB 1 to 8: Use these keys to edit the displayed byte in the current word
pattern. Each key will toggle one bit in the displayed byte.
·
·
CLEAR: Pressing this key forces all bits in the displayed byte to 0.
SET: Pressing this key forces all bits in the displayed byte to 1.
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Functional Overview
Function (Soft) Keys (F1, F2, F3, and F4)
Menu Functions: The primary use of the function keys in the Generator and
Analyzer is to access and navigate each instrument's menu system. F1 may be
thought of as the main menu key. Pressing F1 will display the instrument's first
level menu. Once inside the menu system, you may use the F1, F2, F3, and F4
keys to select different menus, or to make choices within a selected menu. Note
that pressing the F1 key enough times will always get you out of the system. See
Chapter 3 - Reference for an explanation of each Generator and Analyzer menu.
Analyzer Inputs
These function keys provide signal inputs and control of parameters (Input
Termination, Threshold, Logic Polarity and Data/Clock Phase Delay) for DATA,
Ref DATA, and CLOCK.
Selecting DELAY, V-TERM or V-THRS permits the INPUT Up/Down keys to
vary the Input parameters for DATA, as described below. Holding the Up/Down
key repeats the function five times a second.
Function key F2 (CLOCK) permits the V-TERM key to vary only the Input
termination parameters for CLOCK.
Function key F3 (Ref DATA) permits the DELAY, V-THRS, and V-TERM keys
to vary the Input parameters for Reference DATA.
DELAY - Pressing DELAY selects Input Data Delay adjust mode. The Input
Data signal can be delayed over the range 0.0 nS to 3.9 nS in sub-nanosecond
steps. The delay is modified with the INPUT Up/Down keys. The current Delay
is displayed on the lower left side of the LCD.
An illuminated Delay LED light indicates that the unit's DELAY can be modified
by the Up/Down arrow keys.
V-TERM - Pressing V-TERM selects V-termination mode. The input
termination voltage for Input Data is selectable between GND, -2.0V, and AC.
-2.0V mode provides active termination for ECL and GaAs signals. AC mode
allows RF termination.
An illuminated V-TERM LED light indicates that the input termination can be
modified by the Up/Down arrow keys.
V-THRS - Pressing V-THRS selects V-Threshold mode. The Input Data
threshold is variable over the range of -1.5V to +1V in 50 mV steps. The
currently selected threshold voltage is displayed in the lower right side of the
LCD display.
An illuminated V-THRS LED light indicates that the threshold voltage can be
modified by the Up/Down arrow keys.
The Data threshold voltage is available at the Analyzer rear panel SMA jack
labeled DATA THRESHOLD.
Print Setup Function (Analyzer only): You can print a report showing the
current setup of the Analyzer by pressing the F4 key. This function, however, is
not active in the menu mode.
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Functional Overview
Generator ERROR INJECT Section
Controls in the ERROR INJECT section are used to set up the Generator's error
injection function.
ERROR INJECT
RATE SINGLE
·
·
RATE: Press this control one or more times to select an internal error inject
rate, or the external error inject mode.
SINGLE: When the error inject function is set to single (ERR OFF), press
this key to inject single errors. Or, when the error inject function is set to an
internal rate, or to external, use this key to turn error injection off. Note that
you could then press the RATE key to turn error injection back on at the
same rate as before.
·
Error Inject (LED): The LED in the ERROR INJECT section will flash
once for each injected error.
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Functional Overview
Analyzer INPUT Section
The controls shown below are used to set up the Analyzer clock and data inputs.
INPUT
DELAY
V-TERM V-THRESH
D-INV
EXT
REFERENCE DATA
CLOCK
CLOCK
DATA
DATA
(1)
(1)(2)
50 Ohm, 2V MAX
50 Ohm, 1.5V MAX
·
·
·
DELAY: Press this key to add delay to the DATA or REF DATA inputs to
adjust the clock/data phase relationship. Note that the Auto_Search function
will automatically set data delay to a value which provides the maximum
noise immunity, that is so that the active (falling) edge of the clock falls in
the middle of data bit time slots.
V-THRESH: Press this key to set the input decision threshold for the
DATA and REF DATA inputs. Note that threshold does not apply when
differential operation is selected. Function keys F2 and F3 are OFF when
programming DATA. Function key F3 is ON when programming REF
DATA.
V-TERM: Press this key to select the input terminations for the DATA,
CLOCK, or REF DATA inputs. Available selections are: (GND, -2 V, or
AC). See table below.
·
·
D-INV: Press this key to select either the data non-inverted (LED off) or
data inverted (LED on) mode.
EXT: This is an input for an external data reference signal.
NOTE: Use the F2 and F3 function keys to determine which input will be
affected by the DELAY, V-THRESH, and V-TERM controls as follows:
F2
off
on
off
on
F3
off
off
on
on
Affected Input
DATA
Allowable Control
V-TERM, V-THRESH, DELAY
V-TERM only
CLOCK
REF DATA
not allowed
V-TERM, V-THRESH, DELAY
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Functional Overview
Analyzer Error History Section
SYNC LOSS
BIT
CLEAR
PHASE
POWER
SYNC LOSS
The SYNC LOSS LED is lit when the unit is not synchronized, it will remain lit
until cleared by the user.
The BIT LED is lit when bit errors occurs, and remains lit until it is cleared by the
user.
BIT
PHASE
The PHASE LED is lit when the guaranteed setup or hold time of the GB1400
input decision circuit is violated. This indicates to the user that the errors that are
occurring may be due to input clock/data timing or signal level.
The POWER LED is lit when the unit powers up. It remains lit until it is cleared
by the user. It is used to indicate that the unit lost power during a long term
(overnight) test.
POWER
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Functional Overview
Analyzer ERROR DETECTION Section
The ERROR DETECTION section contains test setup and display controls.
ERROR DETECTION
DISPLAY
SYNC
CLEAR
LOCK
AUTO
AUDIO
VOL
RATE
SEARCH
DISABLE
DISPLAY SELECT: Use this control to select which results are displayed in
the Bit Error Rate (BER) fields. The options are Window, Totalize, or Test.
·
·
CLEAR: Press this key to clear previous results and to start/stop timed tests.
AUDIO VOL (• ,¯ ): Use these keys to increase or decrease the volume of
the Analyzer's error beeper function.
·
AUDIO RATE (• ,¯ ): Use these keys to increase or decrease the error rate
threshold of the beeper function. Selections are 1E-x, where x = 2, 3, ... 16.
Analyzer SYNC Controls
The ERROR DETECTION section contains the following SYNC controls which
are used to set up the Analyzer's automatic synchronization functions:
·
AUTO SEARCH: Press this key to enable (LED on) or disable (LED off)
AUTO SEARCH. With AUTO SEARCH enabled, each time BER goes above
the synchronization threshold (LOCK LED turns off) the Analyzer will
automatically attempt to:
1. set the decision level for the DATA inputs,
2. set input DATA delay,
3. determine which PRBS or short word pattern is being received, and
4. determine if the pattern is inverted or not.
·
·
DISABLE: Use this key to enable or disable automatic pattern re-
synchronization. If DISABLE is off, then the Analyzer will automatically
try to resynchronize its pattern detector (by looking for a new pattern
alignment) when BER goes above the current synchronization threshold. If
DISABLE is on, the Analyzer will not attempt to resynchronize regardless of
the BER. This allows for very high BER measurements.
This key controls the "clock slip" operation of the BERT. An illuminated
DISABLE LED indicates the synchronization (clock slip) circuit is disabled.
LOCK (indicator): This indicator turns ON when BER is less than the
current synchronization threshold, and OFF when BER is greater than or
equal to this threshold.
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Functional Overview
Burst Mode Option
The standard GB1400 operates over a clock frequency range of 1 Mbit/s to 1400
Mbit/s. The GB1400 Tx has an internal clock source that has a range of 1 MHz to
1400 MHz. It also has a provision for using an external clock source of the same
frequency range. When using the external clock source, it must be applied
continuously without interruption. The GB1400 RX also requires that, at all
times during the test, a clock signal within the 1 Mbit/s to 1400 Mbit/s frequency
range be continuously applied. If the external clock signal should be removed , or
go below 1 MHz for any reason during the test, the RX will register OUT OF
SYNC as soon as the clock signal is reapplied. This condition will initiate a
resynchronization of the receiver and restart any tests.
For the Burst Mode option, the GB1400 RX has been modified to work normally
or in Burst Mode from 150 kHz to the normal 1400 MHz upper limit. The RX
CLOCK and CLOCK BAR inputs have been modified for DC operation. This
modification requires the removal of any blocking capacitors in the input path.
The removal of the capacitors limits the allowable input signal to ECL levels
only. Levels other than ECL may damage the input circuitry. The three standard
clock input termination selections of GND, AC, and -2V are still present.
Note: The Clock may be used either differentially or single-ended. To use a
single-ended clock input, connect the ECL clock input to the CLOCK input
connector. Select the -2V input termination, and connect DC bias voltage of -1.3
VDC to the CLOCK BAR input connector.
These and other changes will now allow the receiver to maintain synchronization
whenever CLOCK and DATA are synchronously stopped and started during a
test pattern, providing there has not been a bit slip between CLOCK and DATA.
In both the Tx and RX, there can be any length of time that both CLOCK and
DATA are off, and the minimum CLOCK/DATA applied can be as low as a
single cycle, providing the minimum of 714 pS and maximum of 667 ms clock
period restrictions are observed.
Similar Tx circuit changes allow the Tx DATA and CLOCK outputs to follow,
cycle by cycle, the input from a bursted External Clock Input. This means that
the Tx can be used in a start-stop, or "Burst Mode".
For every clock cycle into the External Clock Input, there will be the same
number of clock cycles and data bits output through the clock and data outputs.
The time between clock cycle inputs is unrestricted and can be any length of
time. The number of clock cycles can be any number from continuous to a single
cycle. During the time there is no clock input to the External Clock Input, the
internal code generator is idle (not running). Each clock cycle steps the code
generator by one bit. Clock cycle period must not be more than 667 ms (150
kHz) nor less than 714 pS (1400 MHz).
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Functional Overview
Burst Mode Usage
The Burst Mode option of the GB1400 will find usage in applications where
traditional BERTs cannot operate. Traditional BERTs require a continuous
CLOCK and DATA signal with no interruption. Should interruptions occur, the
RX will resynchronize or indicate errors that actually did not occur due to the
asynchronous re-start. The BURST MODE allows operation with a non-
continuous clock.
There are communications and telemetry systems that do not necessarily send
data continuously. These systems send data in "bursts" with variable times of
inactivity between bursts. Traditional BERTs cannot accurately check these
systems, especially if the bursts are of short duration. A traditional BERT may
require more bits than are available in the burst to (re)synchronize. Even if the
bursts are large, many bits in the burst would not be checked during the
(re)synchronization procedure.
In Burst Mode, the GB1400 RX will follow the input CLOCK and DATA
without regard for inactive time between bursts. The only requirement is that
there be no bit slips between the CLOCK and DATA at the Tx or UUT and there
be a clock cycle for every DATA bit received.
See figures on the next page for Transmit and Receive Operation with Burst
Mode.
Specifications for Burst Mode
·
·
·
Maximum time between bursts - no restriction
Minimum time between bursts - one clock period
RX Clock Input - ECL level only; User-selectable termination 50 Ohms to
-2V should be used. Minimum rate during burst - 150 kbit/s; Maximum rate
during burst - 1400 Mbit/s
·
·
RX Auto Search restriction - Below 500 kbit/s, the Auto Search function can
take a very long time due to code word search. Finding both Threshold and
Delay is rapid, but Data Pattern search is lengthy. Because of this, the user
should use Manual Search Mode to keep synchronization time as low as
possible.
Restriction on other options - None
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Functional Overview
Undefined Time
………………..
Undefined Time
………………..
Ext Clk In
Clk Out
………………..
………………..
………………..
………………..
Data Out
Data Value
1
0
1
1
0
0
Figure 2-9. Transmitter Burst Mode Option
[ Sync Time
] [
Measurement
A
DATA
Sync
Attained
Undefined Time
|------|
Sync Attained
|
B
DATA
[Msmt
]
[ Sync
] [Measurement
]
Start Resync
C
DATA
[Msmt
]
[Measurement
]
[Msmt
]
Figure 2-10. Receiver Burst Mode Operation
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Functional Overview
PECL Option for GB1400 Tx
The PECL option is available for the GB1400 Tx only. The PECL option for the
GB1400 Tx is a modification that allows for an increased OFFSET RANGE for
the clock and data outputs, so that the user will be able to generate PECL levels
for testing in a PECL environment. PECL is defined as ECL operating +5.0 V
above ground.
Example:
ECL Levels
VOH » -.9V
VOL » -1.8V
VBB » -1.35V
VTT » -2.0V
PECL Levels
VOH » +4.1V
VOL » +3.2V
VBB » +3.65V
VTT » +3.0V
The GB1400 front panel displays, the clock and data amplitude and offset based
on a load of 50 Ohms to ground.
The inverted output circuit is identical to the true output circuit.
In the PECL system, Vtt = +3.0V, therefore, the resulting GB1400 Tx signal will
be shifted by +1.5V. To get PECL levels at the GB1400 Tx output, set the unit
levels as follows:
Display Setting
Resulting PECL Levels
(50 Ohms to +3.0V)
AMP = .90V
VOH » +4.10V
OFFSET = +1.7V
VOL » +3.20V
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Tutorial
Basic BERT testing with the GB1400
A critical element in digital transmission systems is how error-free its
transmissions are. This measurement is made by a bit-error-rate tester (BERT).
The GB1400 Generator (Tx) and Analyzer (Rx) are designed to operate at bit
rates up to 1400 Mb/s. These portable instruments provide PRBS or User
Defined Patterns (up to 1Mbit deep) for high speed BERT testing.
Objective of Tutorial
Understand GB1400 instrument setup for BER testing using PRBS patterns.
Procedure
This tutorial programs the GB1400 Generator to provide PRBS clock and data
signals for the Analyzer. Using AUTO-SEARCH features, the Analyzer will
synchronize to the incoming PRBS test pattern. Bit Error Rate (BER)
measurements will be performed on both good (error-free) and bad (user injected
faults) data streams.
Key Feature of Tutorial
This lab demonstrates the use of AUTO-SEARCH Synchronization.
Equipment Required
Description
Qty Part Number
Source
Tek
GB1400 Generator
GB1400 Analyzer
1
1
3
GB1400 Tx
GB1400 Rx
174-1341-00
Tek
Tek
50W Coax SMA cables, 1 meter
length, male to male
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Instrument Connections and Controls
Data Threshold connection (required
for single-ended signals)
GB1400 Analyzer (Receiver)
DATA
CLOCK
GB1400 Generator (Transmitter)
CLOCK
CLOCK
DATA
DATA
1.
Setup units with default settings
Note: Resetting the unit to factory defaults is used infrequently. It helps simplify
instructions on this beginners lab. A customer would not normally do this as
they would lose their stored setups.
To reset the units to their factory default setting, you must hold down three
separate keys while turning on the front panel power switch. Power the
Generator while pressing and holding its VIEW ANGLE, MSB 1 and (PATTERN) CLEAR
keys simultaneously. Release the key after the message Default Settings appears in
the display. Repeat this procedure with the Analyzer. This will force both the
Generator and Analyzer to power up using factory default settings.
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2.
Connect the Generator to the Analyzer.
Connect the generator and analyzer as shown below. The generator CLOCK output
connects to the analyzer CLOCK input. The generator DATA output connects to the
analyzer DATA input. The rear panel THRESHOLD output on the Rx connects to the
Receiver NOT-DATA input on the front panel. Terminate the generator NOT_CLOCK
and NOT_DATA signals with the 50W terminators located on the front panel of the
generator.
rear panel
threshold output
GB1400 TX
clk clk data data
data
GB1400 RX
clk clk
data data
clock
Note: Do not mix up the clock, not_clock, data, and not_data signals or tutorial
results will be different.
3.
Setup Generator for PRBS-23 Mode.
Locate the controls in the OUTPUT box of the Generator. Setup the Generator
clock and data outputs as follows:
Set this parameter
…to this value
…using this procedure.
DATA amplitude.
1 volts
Press the DATA key. The LED within the switch
should be lit.
Press AMPLITUDE up/down keys until data
amplitude is set to 2.00V.
DATA baseline offset
CLOCK amplitude
-0.5 volt
1 volts
Press BASELINE OFFSET up/down keys until
data baseline offset is set to -0.50V.
Press CLOCK. (the LED within switch should be
lit).
Press AMPLITUDE up/down keys until clock
amplitude is set to 2.00V.
CLOCK baseline
offset
-0.5 volt
Press BASELINE OFFSET up/down keys until
clock baseline OFFSET is set to -0.50V.
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B.
Locate the controls in the PATTERN box of the Generator. Make sure the
PRBS button is enabled (the LED inside this switch should be ON). Set the
23
Generator pattern to a 2 -1 bitPRBS as follows:
Set this parameter
PRBS type
…to this value
…using this procedure.
PN 23
Press pattern up/down arrow keys until
PATTERN is set to PN 23
C.
Locate the controls in the ERROR INJECT box of the Generator. Verify
that the Generator ERROR RATE GENERATOR is OFF (the LED within the switch should
be OFF). If the LED in the error inject RATE key is ON, then press RATE one or
more times until it turns off.
4.
Setup Analyzer for “AUTO-SEARCH” Operation.
A.
Locate the controls in the SYNC box of the Analyzer. Verify that the
Analyzer AUTO SEARCH function is ENABLED. The LED in the AUTO SEARCH key
should be ON. If the LED is OFF, press the AUTO SEARCH function one time until
the LED is ON. At this point, verify that the green LOCK LED is ON.
B.
Locate the controls in the ERROR DETECTION box of the Analyzer. Zero
all Analyzer error counts by pressing the CLEAR key. Confirm that the number of
errors and the error rate were reset to 0 (note: error rate will start changing as
more and more bits are received. After several minutes of operation, the error
rate should reach 0.0E-9 Þ 0.0E-10 Þ 0.0E-11 and on).
C.
Locate the controls in the ERROR HISTORY box of the Analyzer. Reset all
Analyzer history LEDs by pressing this CLEAR key. Confirm that all ERROR
HISTORY LED’s are turned OFF.
D.
Locate the controls in the ERROR INJECT box of the Generator. Verify the
GB1400 Analyzer can detect errors by pressing the Generator ERROR INJECT
SINGLE key several times. Verify that the number of errors count displayed by
the Analyzer increments each time the Generator SINGLE key is pressed.
In effect you are now performing a bit error rate test on the test cables connecting
the gigaBERT1400 Generator and Analyzer. In an actual BER test,
gigaBERT1400 Generator clock and data outputs would be connected to inputs
on a "device under test" (DUT) while gigaBERT1400 Analyzer inputs would be
connected to outputs on the DUT.
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5.
Change the PRBS pattern type
These steps demonstrate one of the many benefits of our Full-Featured Auto-
Search algorithm - automatic synchronization to the incoming signal by selecting
the correct PRBS test pattern.
A.
Locate the controls in the PATTERN box of the Generator. Make sure the
PRBS button is enabled (the LED inside this switch should be ON). Set the
Generator pattern to a 27 PRBS as follows:
Set this parameter
…to this value
…using this procedure.
PRBS type
PN 7
Press pattern up/down arrow keys until
PATTERN is set to PN 7
As the PRBS pattern type is changed, the Analyzer will start searching for a
match. You should see the BIT, PHASE, and SYNC LOSS LED’s turn ON in the Error
History section of the Analyzer. While the Analyzer is searching for the correct
PRBS type, the LOCK LED in the Error Detection Section should turn OFF. When
synchronization is achieved, the LOCK LED should turn ON.
B.
Locate the controls in the ERROR DETECTION box of the Analyzer. Zero
all Analyzer error counts by pressing the CLEAR key.
C. Locate the controls in the ERROR HISTORY box of the Analyzer. Reset all
Analyzer history LEDs by pressing this CLEAR key. Confirm that all ERROR
HISTORY LED’s are turned OFF.
D.
Locate the controls in the ERROR INJECT box of the Generator. Press the
ERROR INJECT SINGLE key several times. Verify that the error count
displayed by the Analyzer increments each time the Generator SINGLE
key is pressed. Verify the BIT LED light located in the Error History
Section of the Analyzer turns on.
6.
Turn off AUTO - SEARCH and change Generator Outputs
These steps demonstrate one of the many benefits of our Full-Featured Auto-
Search algorithm - setting the input data decision voltage to its optimum value.
While the Auto-Search feature is disabled, the Generator output voltage will be
adjusted to cause loss of sync. Auto-Search will then be enabled to correct this
synchronization problem.
A.
Locate the controls in the SYNC box of the Analyzer. Disable the AUTO
SEARCH function by pressing the AUTO SEARCH key. The amber LED within this
switch will be OFF when the Analyzer AUTO SEARCH function is DISABLED. If the
LED is ON, press the AUTO SEARCH function one time to turn the LED OFF.
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B.
Locate the controls in the OUTPUT box of the Generator. Adjust the Data
amplitude and offset as follows:
Caution: Adjust only the DATA signal. Do not change the CLOCK signal.
Set this parameter
…to this value
…using this procedure.
DATA amplitude.
0.50 volts
Press the DATA key. The LED within the switch
should be lit.
Press AMPLITUDE up/down keys until data
amplitude is set to 0.50V.
DATA baseline offset
-0.25 volts
Press BASELINE OFFSET up/down keys until
data baseline offset is set to -0.25V.
If you examined this output data signal (voltage vs. time) on a scope, it would
look similar to:
+0.25
¬¬ Maximum Level
•
0.5 V
amplitude
¯
¬¬ Optimum Threshold
+0.00
-0.25
-0.50
•
½
½
¬¬ Minimum Level
Voltage
•
-0.25 V
best value to use for THIS data
time ®
data offset
threshold is ~0.00Vdc + 0.05Vdc
You will now be manually adjusting the data input threshold for the GB1400
Analyzer. Locate the controls in the PATTERN box of the Analyzer. Make sure
F2 and F3 are turned OFF. These switches are used when adjusting
CLOCK or REF DATA input parameters.
C.
Locate the controls in the INPUT box of the Analyzer. Verify that the
Analyzer THRESH LED is turnedON. This allows manual adjustment of the DATA
Input threshold. The threshold for the selected signal (clock or data) is shown on
the bottom line of the Analyzer’s alpha-numeric status display. Using the INPUT
UP/DOWN keys, adjust this threshold and confirm the following actions:
Note: The BER display on the Analyzer can be set to totalize, window, or test
modes. When in the totalize mode, a small¥ (infinity) symbol will be displayed
before the BER error rate. Use totalize mode for this tutorial exercise. Press the
ERROR DETECTION DISPLAY key several times to setup the analyzer for totalize
mode..
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Set DATA
THRESHOLD
to this value
Verify these results on the Analyzer
Comments
Press the ERROR DETECTION and ERROR
HISTORY “CLEAR KEYS”, then confirm:
Data signal not detected. Selected
threshold is below the minimum level of
your data signal.
-0.50 volts
SYNC LOSS and BIT LED’s are ON
SYNC LOCK LED is OFF
ERROR RATE display shows “NO
DATA” or a 50% Error Rate.
Press the ERROR DETECTION and ERROR
HISTORY “CLEAR KEYS”, then confirm:
You are starting to detect the data signal.
Selected threshold is near the minimum
level of your data signal. Data threshold
is NOT CORRECT and you should expect
BER errors.
Approximately
-0.30 volts
to
SYNC LOSS should turn OFF
BIT and PHASE LED’s should turn ON
SYNC LOCK LED should turn ON
-0.25 volts
Press the ERROR DETECTION and ERROR
HISTORY “CLEAR KEYS”, then confirm:
Data signal fully detected. Selected
threshold is at an optimum value for the
input data signal. This is typically =
1/2*[max level - min level].
+0.00 volts
SYNC LOSS should turn OFF
Signal levels detected above this
threshold are considered a logical “1”
and signal levels below this threshold are
considered a logical “0”.
BIT and PHASE LED’s should turn OFF
SYNC LOCK LED should turn ON
ERROR RATE display shows NO BER
ERRORS equivalent to a rate of
0.0E-9 or better.
Press the ERROR DETECTION and ERROR
HISTORY “CLEAR KEYS”, then confirm:
Data signal not detected. Selected
threshold is above the maximum level of
your data signal.
+1.00 volts
SYNC LOSS and BIT LED’s are ON
SYNC LOCK LED is OFF
ERROR RATE display shows “NO
DATA” or a 50% Error Rate
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D.
Locate the controls in the SYNC box of the Analyzer. Verify that the
AUTO SEARCH function is ENABLED. The LED in the AUTO SEARCH key should be ON.
If the LED is OFF, press the AUTO SEARCH function one time to turn the ON. At
this point, verify that the green LOCK LED is ON.
The Analyzer will now search and calculate a new data threshold. What is the
value of the threshold selected by Auto-Search? You should expect to see this
threshold value within a few hundred millivolts of the “data signal mid-point (or
optimum threshold).
Note - Common Setup Problems
·
·
·
·
Connecting the Generator’s clock output to the Analyzer’s not-clock (clock-
bar) input
Connecting the Generator’s data output to the Analyzer’s not-data (data-bar)
input
Changing Generator’s CLOCK amplitude/offset when lab calls for
adjustments to DATA signals
Failure to connect the external DATA THRESHOLD cable from rear of unit
to NOT_DATA input.
This Concludes the Tutorial.
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Applications
Application Note
Method For Very Fast Automatic Receiver Synchronization
And Eye Width Measurement
Two Auto Search Synchronization Methods
This application note describes two Auto Search synchronization methods used
in the GB1400 Bit Error Rate test set - a FAST method and a BER method. The
criteria and sequence of events for the two methods are compared and the
differences are described.
Auto Search is the feature that the GB1400 uses to describe its method of
automatic setup and synchronization. Both methods of Auto Search
synchronization perform the following functions, but in different ways and with
differing results depending on the type of data and its quality.
·
Analysis of the input data signal amplitude to select the correct threshold
voltage.
·
Determine the timing skew between the clock and data signals and
automatically optimize it.
·
·
Determine the correct data sequence and whether it is inverted.
Measure the data eye width.
So that the following explanations are clear, let us first define some terms.
V–THRESHOLD
This is the absolute DC level above which GB1400 Receiver will declare a data
bit value of “1” (HIGH). Below this value, it is considered to be a “0” (LOW).
DELAY
This is the timing difference (skew) between ideal timing and actual timing
between the incoming clock and data. Ideal timing will place the falling edge of
the clock signal in the center of the data bit. Any deviation from the ideal should,
when possible, be corrected by delaying either the clock or the data (as in the
GB1400 Receiver) in relation to each other.
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Application Note - Auto Search Synchronization
PHASE
This is a unique and very fast method of determining where the edge of a data bit
is in relation with the clock. The determination of phase errors is done by
monitoring the logic value of a data bit at the selected threshold voltage and
delay at two slightly different times. If the logic value is the same at the two
different times, then a phase error has not occurred. This method will work well
with any data that is relatively noise, jitter and glitch free.
SYNCHRONIZATION
When we state that “the receiver is synchronized”, we mean that the GB1400
Receiver’s internal reference data pattern generator is bit for bit properly aligned
with the incoming data from the device under test. When in synchronization, the
receiver can perform a bit for bit check of the incoming data against its internal
reference to determine bit errors.
DATA POLARITY
This refers to whether the device under test has inverted the data logic in relation
to what was input to it.
DATA EYE
This is a method of showing the data in a visual form. It is displayed on an
oscilloscope using the clock as a trigger, and the data into the vertical amplifier.
Case 1 of Diagram 1 of this application note is an example of data eye.
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Application Note - Auto Search Synchronization
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Application Note - Auto Search Synchronization
I. Auto Search Algorithm – “Fast” Method
Auto Search will determine the Data V- Threshold, Data Delay, Data Pattern and
Polarity automatically. The so called “FAST” method has been given its name
because of the speed with which it determines the threshold voltage setting,
delay, data pattern and polarity. This is the default method used by the GB1400
Receiver.
The speed is derived mainly from the use of the GB1400’s PHASE edge
detection circuitry which enables the receiver to quickly determine the transition
points of the eye without regard to the actual pattern, or even if the receiver is
properly linked up to the incoming data pattern.
If the data is not clean (glitches, excessive jitter or noise) this method will
possibly not work well. For these cases, use the “BER” method described later in
this document.
The “FAST” method of determining the proper settings for the V-Threshold,
Delay, Pattern and Polarity is as follows:
Auto Search will find the DATA V-THRESHOLD voltage.
1. The receiver examines DATA ACTIVITY at each of the V-THRESHOLD
settings.
2. The receiver then locates and uses the middle of the largest voltage range
which has data activity. If no activity is detected, or if the range of activity is
less than 250 mV, then the receiver indicates “NO DATA” has been
detected.
Auto Search will find the DATA DELAY.
1. For each delay setting, the receiver keeps track of the PHASE indication.
2. It then locates the largest contiguous block of delay settings without any
PHASE indication.
If BOTH ends of the clear block are within the 4 nS, delay range of the
receiver, it then sets the delay to the middle of the block. A measured eye
width is available.
If BOTH ends of the clear block are the edges of the receiver delay range (no
crossing found), it then sets the delay to the middle of its delay range (1.995
nS). No eye width is available.
If NO clear block is found (no crossing found); it then sets the delay to the
middle of its delay range (1.995nS). No eye width is available.
If ONE end of the clear block is on the edge and the width of the clear block
is less than half the data period, it then sets the delay to that edge (0 or
3.99nS). No eye width available.
If ONE end of the clear block is on the edge and the width of the clear block
is greater than half the data period, it then sets the delay to be away from the
found crossing by half the clock period. A calculated eye width is available.
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Application Note - Auto Search Synchronization
Auto Search will find the DATA PATTERN and POLARITY.
1. The receiver then attempts to SYNC on each data pattern and Polarity (10
possibilities). If sync is found, STOP.
2. Attempt the previous step ten times. If the pattern is not found after ten
times, go back to "Find Data V-Threshold".
II. AUTO SEARCH Algorithm – BER Method
Like the “FAST” method of Auto Search, the “BER” method will also determine
the V-Threshold, data delay, data pattern and polarity. For this method to work,
the receiver is sensitive to the data it is analyzing and must be synchronized with
the incoming data.
This method requires the user to set criteria pertaining to Bit Error Rate threshold
and sample size that is used to determine the size and center of the data eye.
Because of the adjustability of the threshold and sample size, this method can be
made less susceptible to noise and glitches. The methods involved in analyzing
the data are quite rigorous and can require considerably more time than the
“FAST” method.
Since the GB1400 is capable of measuring and displaying "eye width", the
SAMPLE and BER THRESHOLD criteria requirements in the BER method, if
selected intelligently, tend to yield more accuracy and repeatability and is less
subject to glitches, noise, and jitter than the "FAST" method
The Auto Search BER method of determining the proper settings of the V-
Threshold, Patter, Polarity and Delay is as follows:
Auto Search will find the DATA V–THRESHOLD voltage.
1. The receiver examines DATA ACTIVITY at each of the V – THRESHOLD
settings.
2. The receiver then locates and uses the middle of the largest voltage range
which has data activity. If no activity is detected, or if the range of activity is
less than 250 mV, then the receiver indicates “NO DATA” has been
detected.
Auto Search will then attempt to find the DATA PATTERN.
This is because the data pattern needed to be able to do the BER measurements.
1. The receiver first sets the data delay to 0pS and attempts to SYNC on each
data pattern and polarity (10 possibilities). If found, go to the section
Determine Data Delay below.
2. The receiver then sets the data delay to 1/2 of the clock period and attempts
to sync on patterns (see step 2a above). If it is found, then go to the section
Determine Data Delay below. (If the frequency is less than 250 MHz, the
receiver will use 4nS instead of the incoming clock period throughout Find
Data Pattern)
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Application Note - Auto Search Synchronization
3. If unsuccessful, it will then try the following data delays in the previous step-
1/4 per, 3/4 per, 1/8 per, 5/8 per, 3/8 per, 7/8 per.
4. If sync is still not found, go back to the first section Find Data V-Threshold.
Auto Search will determine the Data Delay.
1. Initially the entire delay range (0nS to 3.99 nS) in steps of 70pS will be
sampled for 20mS each for error rate. The selectable BER Threshold will be
used to determine if the delay settings are within the data eye crossings.
2. The largest contiguous block of delay measurements with error rates below
the threshold will be found. Using that data, the transitions from data
crossing to data eye can be found.
NOTE: This will be with 70 pS granularity.
If two transitions are within the receiver delay range, two points will be re-
examined such that the data eye center and width can be determined. (See
illustration /diagram #1, Case #1).
If BOTH ends of the clear block are the edges of the receiver delay range (no
Crossing found), set the delay to the middle of the receiver delay range.
STOP. No eye width is available.
If NO clear block is found (no crossing found), set the delay to the middle of
the receiver delay range.
STOP. No eye width is available.
If ONE end of the clear block is on the edge and the width of the clear block
is less than half the clock period, set the delay to that edge.
STOP. No eye width is available.
If ONE end of the clear block is on the edge and the width of the clear block
is greater than half the clock period, two transition points, A and B, will be
re-examined further (see Diagram 1, Cases 2 and 3).
3. If the transition points are to be evaluated further, an area 70pS wide will be
examined in steps of 5pS for 20ms each. This starts from the first delay
setting in the data crossing and goes to the first delay setting in the data eye
(see Diagram 2).
4. After the areas have been measured for error rate, the areas will be examined
for the first transition from below the threshold to above the threshold staring
with the end closest to the data eye center. These points will be the NEW
transition points.
5. Each of these NEW transition points will be re-examined for a length of time
based upon the SAMPLE size. The error rate will be compared with the
selectable BER Threshold.
If the error rate is below the Threshold, the next point away from the Data
Eye Center will be examined, and so on, until the error rate transitions to
above the Threshold. The last point below the Threshold will be the TRUE
transition point.
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Application Note - Auto Search Synchronization
If the error rate is above the Threshold, the next point toward the Data Eye
Center will be examined, and so on, until the error rate transitions to below
the Threshold. The first point below the Threshold will be the TRUE
transition point.
6. After the new transition points are re-examined and the TRUE transition
points are found, the delay will be set as follows:
For Case 1, the delay will be set to the middle of the two TRU transition
points (point C).
For Cases 2 and 3, the delay will be set to be away from the middle of the
TRUE transition points by half the data clock period (point C).
7. Eye Width Measurement
In the previous step above, if the error rate is below the threshold, the
measured eye width is the point B delay measurement minus the point A
delay measurement in Diagram 1, Case 1. STOP.
In the previous step above, if the error rate is above the threshold, the
calculated eye width for Diagram 1 Case 2 is the delay measurement at point
A minus the delay measurement at point C, times two. STOP.
In the previous step above, if the error rate is above the threshold, the
calculated eye width for Diagram 1, Case 3 is the delay measurement at point
C minus the delay measurement at point B, times two. STOP.
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Application Note - Auto Search Synchronization
Consideration In Determining The Eye Data Width
In most circumstances a test signal data eye displayed on an oscilloscope will
appear to be larger than that reported by the GB1400 Receiver. This is expected
and is due to several factors. One is that low error rates are virtually impossible
to see on an oscilloscope. Other factors such as set-up and hold time and signal
characteristics will all have an effect on the measurement by decreasing the
apparent eye size.
The value of an eye width measurement made on the GB1400 is when it is used
in a relative manner. If a device is determined to be working correctly using a
known good signal, its eye width can be measured on the GB1400 Receiver. That
measurement can be used as stable reference standard against which all other
devices can be measured. It is not possible for the GB1400 Receiver to duplicate
all characteristics of the actual device that will be connected in its place, but it
will usually suffice as a reasonable approximation.
Consideration In Determining The Data Eye Center
In theory, a plot of bit error versus delay setting will show a smooth curve,
almost linear, which has no aberrations and transitions from horizontal to almost
vertical at the data eye crossing. For a signal with this curve (a clean signal with
no aberrations, jitter or wander), the measurement of the data eye center will be
consistent using either of the methods.
In typical applications, the method which will assure a repeatable measurement
of the data eye center is to measure each and every delay setting for a significant
number of data bits. Because of probable aberrations in the data signals,
measuring coarsely over the delay (using 70pS steps) MAY lead to inconsistent
measurements due to the aberrations being seen during one search and not the
next.
Delay Specifications
The GB1400 programmable delay has the following nominal specifications:
Range:
0 – 3.99 Ns
5 pS
Resolution:
Accuracy:
+/- 20 pS
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Application Example
GB700/ GB1400 Optical Component Test
gB-Series Tx
gB-Series Rx
Clock
Clock
Data
Data
Fiber Optic
Clock Recovery
and
Retiming
Fiber Optic Link Test Example
A typical BERT application is measuring the error performance of the electrical-
to-optical (E/O) and optical-to-electrical (O/E) output modules of a fiber optic
transmission system, as shown in the diagram above. Not all fiber optic links are
designed for extremely high speed. For example, many data communications
LANs use FDDI at 133 Mb/s. Serial digital video links operate at 270 Mb/s.
External Clock input shown on the BERT Tx would be used to provide jittered
clock to stress Clock Recovery (CR) circuit.
Longer PRBS patterns, such as 223 might be used to test DC wander
susceptibility of the CR subsystem.
Peak-to-peak amplitude and level offset of the BERT Tx output may be varied to
determine acceptable operating range for the DUT input circuitry.
Tests may be made using short and long fiber cables to be able to specify
maximum allowable length of fiber runs.
Note that in this application, it may be an advantage to be able to separate the
BERT Tx and Rx. Using the BERT internal PRBS generator makes it easy to
assure that the Tx and Rx have the same data for error comparison.
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Application Example
Fibre Channel Link Testing Parallel and High-speed Serial
gigaBERT
(Serial)
Rx
Tx
Parallel stimulus
Parallel results
Rx
O / E
Serial - BUS
BUS - Serial
Rx
BUS
Interface
Tx
Fiber
BUS
Interface
Interface Under Test
gigaBERT
(Serial)
E / O
Tx
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Application Example
Application Example
Testing QPSK Modems, I & Q
I-Channel BERT
GB700/1400 Rx
data
clock
GB700/1400 Tx
Q-Channel BERT
GB700/1400 Rx
I
I
DATA
QPSK
Mod /Demod
CLOCK
CLOCK
data
clock
up to 1400 Mb/s
data rate
Q
Q
GB700/1400 Tx
EXT
CLOCK
INPUT
DATA
CLOCK
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Application Note
Application Example
QPSK BER Testing using PRBS Data for 2-Channel I & Q
I-Channel BERT
GB700/1400 Rx
data
clock
GB700/1400 Tx
DATA
Q-Channel BERT
I
I
GB700/1400 Rx
QPSK Mod / Demod
data
clock
Delay line
or long
Q
Q
DATA
coax cable
CLOCK
CLOCK
Delay line can simulate a PRBS pattern with an offset of n-clock bits.
Both I and Q channels running PRBS data (but offset by n-clocks).
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Menu Overview
A wide range of "auxiliary" setup functions is provided in the GB1400 Generator
and Analyzer Menu systems. To enter the Generator or Analyzer Menu system,
simply press the instrument's F1 key. At this point the format of the display will
change to show the first page of the top level Menu. The top level Menu in both
the Generator and Analyzer contains other Menus and various setup parameters.
Once inside the Menu system, you use the functions keys, F1 ... F4, to navigate
to any Menu function, and to make selections within each Menu function.
Functions Common to Generator (TX) and Analyzer (RX)
AC Power
The GB1400 Generator and Analyzer are both AC powered. The power switch of
both instruments is located on the front panel.
Selecting 115 VAC or 230 VAC Operation
Both the GB1400Generator and Analyzer are equipped with an auto-ranging AC
power supply. This supply will operate over a voltage range of 90 to 250 VAC,
and a frequency range of 47 to 63 Hz. Thus, no setup change is required to
operate from 115 VAC at 60 Hz or 230 VAC at 50 Hz.
Turning Instrument Power ON/OFF
The Generator and Analyzer are equipped with AC power switches on the front
panel.
LCD Viewing Angle
The optimum viewing angle of the GB1400 Generator or Analyzer LCD display
may be adjusted using the VIEW ANGLE control. Each press of the VIEW
ANGLE key will raise the optimum view angle until the highest angle is reached.
The next press of VIEW ANGLE will return optimum viewing angle to its lowest
angle, and so on.
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Recalling the Default Setup
The default setup of the Generator and Analyzer are shown in the Appendix. To
return the Generator or Analyzer to this setup, use the following procedure:
1. Turn instrument power off.
2. While holding down the VIEW ANGLE, MSB 1, and (PATTERN) CLEAR
keys simultaneously, turn instrument power back on.
3. After you see the message Default Settings appear in the display, release the
three keys. In a few seconds the normal display format will appear and the
instrument will be in its default setup.
Locking the Front Panel
The instrument's front panel may be "locked" or "unlocked" using the PANEL
LOCK control. When the front panel is locked, all keys that can cause a setup
change are disabled. It is often useful to lock the front panel during a long or
critical test to prevent accidental loss of test results. Note that the LED in the
PANEL LOCK control indicates whether the front panel is locked (LED on) or
unlocked (LED off).
Simply press the PANEL LOCK control to toggle between the locked (LED on)
and unlocked (LED off) state.
Selecting a Pattern
The following section defines the patterns that can be generated and analyzed by
the GB1400 and how to set up the Generator and Analyzer to use a particular
pattern. Note that the Generator and Analyzer are compatible with the same suite
of test patterns and use the same setup procedures.
Pattern Definitions
The GB1400 can generate and analyze Pseudo-random bit sequence (PRBS) and
WORD test patterns. Each type has its own set of advantages and uses.
PRBS Patterns
Pseudo-random bit sequence (PRBS) patterns are designed to simulate "live
traffic" and have been standardized by the telecommunications and computer
industries. As a result they are often used to characterize or qualify new devices
or systems. Two key characteristics of a PRBS are its overall length in bits and
maximum number of contiguous 0s. The length of a PRBS pattern has the form
n
23
2 -1. For example a 2 -1 PRBS contains 8,388,607 bits. The maximum number
23
of contiguous 0s in a PRBS pattern is n-1, for example 22 in a 2 -1 PRBS.
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The PRBS patterns generated and analyzed by the GB1400 are listed below.
n
Table 3-1. PRBS (2 -1) Test Patterns
n
Label Used in Generator Length
Maximum Number of
Contiguous 0s
and Analyzer Displays
n
(2 -1 bits)
127
7
PN 7
PN 15
PN 17
PN 20
PN 23
6
15
17
20
23
32767
131,071
1048575
8388607
14
16
19
22
Word Patterns
Word patterns are programmable by the user. Word patterns can be designed to
cause specific stress characteristics, such as maximum jitter, or to simulate
framed patterns like SONET, SDH, or FDDI. The standard GB1400 Generator
and Analyzer will allow you to create and save up to ten 16-bit (two-byte)
WORD patterns in battery-backed memory. Or, with the 1-Mbit Option installed,
you can create and save up to ten 64 kbit WORD patterns (depends on buffer
settings) in battery backed memory. Note that the standard and 1-Mbit
instruments also store the current WORD pattern in battery-backed memory.
Selecting the Active Pattern
In this User's Guide, the pattern currently being generated by the Generator or
analyzed by the Analyzer is called the active pattern. Procedures to make a
selected PRBS or WORD the current active pattern are provided below.
Selecting PRBS Patterns
To select a PRBS pattern:
Press the PRBS key. The instrument will now be in the PRBS pattern mode.
Press the pattern up/down keys until the name of the desired PRBS pattern is
displayed. Available PRBS patterns are:
PN 7
PN 15
PN 17
PN 20
PN 23
The displayed PRBS pattern becomes the active pattern immediately.
Selecting the Current Word Pattern
To make the current WORD pattern the active pattern, simply press WORD key.
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Selecting (RECALLing) a Saved Word Pattern
You can recall a WORD pattern using the Generator or Analyzer RECALL
function:
8/16 bit WORD patterns are available on all instruments. Long-WORD (>16-
bits) are available only in units equipped with the 1-Mbit Option.
Use the following procedure to select (recall) a WORD pattern:
Press the WORD key to place instrument in WORD mode.
Press the RECALL key.
Press the pattern up/down keys until the desired WORD or desired mark density
pattern is displayed. Available selections will depend on the programmed WORD
buffer size.
When set to ten 64k buffers, available selections are:
WORD 0
WORD 1
……
WORD 9
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Word Patterns
This section explains how to create, edit, save, and recall WORD patterns using
front panel controls or the Menu system.
Basics
You may create and save up to ten WORD patterns in battery-backed memory
locations WORD 0 through WORD 9. In addition, the current WORD pattern is
stored in battery-backed memory. In standard units, each of the saved WORDs
and the current WORD can contain up to 16 bits. In Generators and Analyzers
equipped with the 1-Mbit Option, which provides additional battery-backed
memory, each of the saved WORDs and the current WORD can contain up to
64kbits (with fewer memory buffers, larger WORD patterns can be saved).
There are three ways to create GB1400 WORD patterns:
Using front panel controls. This is usually the quickest way to create and edit
short patterns. It also can be a practical way to edit a few bytes in long patterns if
these bytes are located near to each other.
Using the Menu system. Because it provides direct byte addressing, this is often
the best method for editing a few widely scattered bytes in long WORD patterns.
The Menu system also provides the FILL function, used to load a user-specified
8-bit pattern into all bytes, and the ORDER function, used to set the bit-order in
each byte to MSB or LSB first. Thus you can use the Menu system to create long
WORDs with simple bit patterns using its byte fill, order, and editing
capabilities.
Downloading: This is the best way to create long WORDs with complex
patterns. Long WORD patterns may be created on an external controller, using a
text editor or specialized software, and downloaded via the instrument's GPIB or
RS-232 ports. Downloading is the only practical way to create simulations of
SONET, SDH, FDDI or other framed signals.
Creating Word Patterns Using Front Panel Controls
Standard Instruments
Use the following procedure to create WORD patterns using front panel controls
in standard instruments, that is Analyzers and Generators not equipped with the
1-Mbit Option:
1. If you are using a previously saved pattern as the basis for the new pattern,
recall this pattern from memory. (See Recalling Word Patterns).
2. Press the WORD key. The LED in the WORD key will turn on (indicating
that the instrument is in the WORD editing mode) and the display will show
the bit sequence of the current WORD pattern in binary format. The WORD
may contain either one or two bytes, that is 8 or 16 bits. Word length (8 or
16) is displayed after the WORD's bit sequence.
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3. If you need to change WORD length, press the WORD LENGTH key and
then the pattern up or down key to toggle WORD length between 8 and 16
bits. When the desired WORD length is displayed, press the WORD key to
return to the WORD editing mode.
4. To select the first or second byte in a 16-bit pattern, press the up or down
key. The selected byte will be indicated in the display by an arrow located
between the two bytes. Byte selection is not required for 8-bit patterns
because the first byte is always selected.
5. To edit the selected byte, press the 1 (MSB) through 8 (LSB) bit keys to
toggle individual bits between 0 (LED off) and 1 (LED on).
6. If you need to edit the other byte in a 16-bit pattern, repeat steps 4. and 5.
Instruments Equipped with 1-Mbit Option
Use the following procedure to create WORD patterns using front panel controls
in instruments that are equipped with the 1-Mbit Option:
1. If you are using a previously saved pattern as the basis for the new pattern,
recall this pattern from memory. (See Recalling Word Patterns).
2. Press the WORD key. The LED in the WORD key will turn on to indicate
that the instrument is in the WORD editing mode. The selected byte in the
current pattern will be displayed in the form AAAAA HH, where AAAAA is
the byte's location or "address" within the current WORD in decimal, and
HH is the value of the selected byte in hexadecimal. Byte address will be in
the range 0, 1, ..., 8192 when BUFFER size is set to 64k or 0, 1, ..., 16384
when BUFFER size is set to 128k.
3. If you need to change WORD length, press the WORD LENGTH key and
then the pattern up/down keys. Pattern lengths of 2048 bytes or less will be
displayed in terms of M bytes plus N bits. Pattern lengths above 2048 bytes
will be displayed in terms of bytes only. When the desired WORD length is
displayed, press the WORD key to return to the WORD editing mode.
4. To select a byte within the current pattern, use the pattern up/down keys to
increment or decrement the displayed byte address.
5. To edit the selected byte, press the 1 (MSB) through 8 (LSB) bit keys to
toggle individual bits. Note that the LED in each bit key indicates whether
the associated bit equals 0 (LED off) or 1 (LED on).
6. Repeat steps 4. and 5. until the WORD has been edited as required.
You have now created a new WORD pattern and may use it to perform tests. The
current pattern is automatically stored in battery-backed memory. However if the
new pattern is important, be sure to save it before creating or RECALLing
another pattern.
See an additional list of remote commands in the Appendix that support the 1-
Mbit Programmable Word option.
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Creating Word Patterns Using Menus
The Menu functions used to create or edit WORD patterns are:
LENGTH
FILL
EDIT and
ORDER.
These functions are located in the WORD Menu. Note that ORDER is a standard
function while the LENGTH, FILL, and EDIT functions are added to the WORD
Menu as part of the 1-Mbit Option. Therefore in standard units, all WORD
editing procedures, except for bit order, are performed using front panel controls.
However in instruments equipped with the 1-Mbit Option, WORD editing may
be performed using either front panel controls or the Menu system, depending on
which approach is more convenient in a given situation.
Note that the WORD Menu also includes the Pattern Sync and SYNC functions.
If you are trying to observe the Data output of the Generator, or the Monitor Data
output of the Analyzer, you may want to use the Pattern Sync Menu to select the
byte location of the pattern synchronization pulse generated by the rear-panel
Pattern Sync output. The SYNC Menu, which appears on the same page of the
Analyzer Menu system, is not directly involved in creating or editing WORD
patterns. Rather, it is used to set the Analyzer pattern synchronization threshold
in terms of BER.
A detailed explanation for each function in the WORD Menu may be found later
in this chapter.
In addition, the general procedure for creating WORD patterns in a Generator or
Analyzer equipped with the 1-Mbit Option is given below:
1. Use the current pattern or recall a previously saved pattern as the basis for
the new pattern. (See Recalling Word Patterns).
2. Press the F1 key to enter the Menu system.
3. Press the F4 key to access the WORD options.
4. If you need to change current WORD length, select the LENGTH Menu by
pressing F3. Enter a new value for length using the F2, F3, and pattern
up/down keys. Then exit the LENGTH Menu by pressing either F4 to set this
new length or F1 to "escape" without making any setup changes.
5. If you want to fill a pattern, select the FILL Menu by pressing F4. Edit the
fill byte using the individual bit keys, 1 (MSB) through 7 (LSB). When done,
exit the FILL Menu by pressing either F4 to automatically load this eight bit
pattern into every byte of the current WORD or F1 to "escape" without
making any setup changes.
6. To edit the current WORD, press F2 to enter the EDIT Menu. Use the F2, F3,
and pattern up/down keys to select a byte within the current WORD. Next,
use the bit keys to edit the displayed byte. Repeat for each byte to be edited.
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When done, exit the EDIT Menu by pressing either F4 to lock in these
changes or F1 to "escape" without making any setup changes.
7. You now may want to access the ORDER and Pattern Sync Menus by
pressing F1 (MORE). The ORDER Menu determines the bit
transmission/analysis order of each byte in the pattern, that is MSB or LSB
first. The Pattern Sync Menu determines the byte location of the pattern sync
pulse in long WORD patterns. When done with these Menus, press the F1
key until the normal display format appears.
You have now created a new WORD pattern and may use it to perform tests. As
noted earlier, the current pattern is automatically stored in battery-backed
memory. However if the new pattern is important, be sure to save it before
creating or recalling another pattern.
Creating Word Patterns Under Remote Control
The third way to create WORD patterns is by remote control.
There are two sets of WORD editing commands: "WORD" and "byte". Word
commands, also known as "short WORD" commands, are part of the standard
command set and are used to perform 8 and 16 bit editing functions.
Byte or "long-WORD" commands, which are added to the GB1400 Generator or
Analyzer command as part of the 1-Mbit Option, are used to perform editing
functions on WORDs of any allowed length up to 16384 bytes. Note that most
WORD commands will function normally in instruments equipped with the 1-
Mbit Option.
This allows instruments equipped with the 1-Mbit Option to operate in automated
test applications designed around the 8/16-bit WORD command set. However
only byte commands may be used to edit long WORD patterns—that is WORDs
that are more than 16 bits long. Therefore a GB1400 Generator or Analyzer must
be equipped with the 1-Mbit Option to function in automated test applications
designed around the byte command set.
A general discussion of GB1400 remote control functions and an explanation of
each remote command may be found in the Appendix. In addition, the general
procedure for using byte commands to create and edit WORD patterns is given
below:
1. All long-WORD editing procedures must start with an EDIT_BEGIN
command, which may have an argument from -1 to +9. An argument of -1
tells the instrument to copy the current WORD pattern into "scratchpad"
memory, while arguments of 0 through 9 tell the instrument to copy the
indicated saved WORD pattern into scratchpad memory.
2. The core of a long-WORD editing procedure is constructed from byte
commands such as BYTE_BLOCK, BYTE_FILL, BYTE_INSERT,
BYTE_EDIT, and BYTE_DELETE. These commands may be used to
download a new pattern into scratchpad memory, or to modify a pattern
previously copied or downloaded into scratchpad memory.
3. All long-WORD (byte) editing procedures must end with an EDIT_END
command. This command may have an argument from -2 to +9. An
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argument of -2 tells the instrument to discard the pattern in scratchpad
memory and not to update the front panel. An argument of -1 tells the
instrument to copy the pattern in scratchpad memory to the current WORD
memory location and to update the front panel. Arguments 0 to +9 tell the
instrument to copy the pattern in scratchpad memory to the indicated (save)
memory location without updating the front panel.
Note that a WORD or byte editing session in a GB1400 Generator or Analyzer
can be started locally from the front panel or remotely via the instrument's
RS-232 or GPIB remote ports. However the instrument will allow only one
editing session to be in-progress at any given time.
Saving Word Patterns (1-Mbit Memory Option)
You can save the current WORD pattern to one of ten WORD memory locations
(WORD 0 to WORD 9), using the following procedure:
1. Press the SAVE key. The LED in the SAVE key should flash to indicate that
you are in the save mode.
2. Press the pattern up/down keys to select a WORD memory location. Note
that the WORD previously stored in this location will be overwritten.
3. Press the SAVE key again to save the current WORD into the selected
location. At this point the SAVE LED will turn off.
Recalling Word Patterns (1-Mbit Memory Option)
To recall a previously saved WORD pattern, use the following procedure:
1. Press RECALL to enter the recall mode. Note that the LED in the RECALL
key turns on.
NOTE: If the current WORD is important and has not been previously
saved, you must save it before pressing RECALL. The recalled pattern will
overwrite the current pattern.
2. Select a WORD pattern memory location by pressing the pattern up/down
keys. The ten possible WORD memory selections are WORD 0 through
WORD 9. The selected WORD becomes the current WORD immediately. In
other WORDs, the current WORD is over-written each time you press the up
or down key.
You can now use the recalled WORD to perform tests. Note that if you want to
edit the recalled WORD, you must press the WORD key again.
Note: The maximum number of WORD patterns is set by the buffer size.
Memory can be partitioned into ten segments of 64kbits; six segments of
128kbits; three segments of 256kbits; one segment of 512kbits; and, zero (0)
segments of 1-Mbit.
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Generator (TX) Functions
This section defines key functions of the GB1400 Generator and how to set up
these functions using front panel controls.
Clock Source and Frequency
The Generator can operate using its internal clock, or an external clock source.
The CLOCK section of the Generator front panel is used to select clock mode
(internal or external), set internal clock frequency, and store or recall user-
defined frequencies. In addition, the CLOCK section contains an input for an
external clock source. When using the internal clock, you may set frequency
directly, or recall one of 10 previously saved frequencies from memory. The
frequency save/recall feature is especially useful if you often switch back and
forth between a limited number of different frequencies.
External Clock Input
When the Generator is in external clock mode, a clock source must be connected
to the connector labeled INPUT in the CLOCK section of the Generator's front
panel. The operating bit rate of the Generator will then be determined by the
frequency of this source. However, when the Generator is set to internal clock
mode, any signal applied to this input will be ignored.
The EXTERNAL CLOCK input is AC-coupled into 50 Ohms (unless BURST
OPTION is installed).
Clock Source
Generator clock source may be set to internal or external using the EXT key in
the CLOCK section. When the LED in the EXT key is off, then clock source is
internal. If the LED is on, the clock source is external and an external source
must be connected to the external clock input (INPUT).
Press the EXT key to toggle clock source between internal and external.
Step Size and Frequency
The frequency of the Generator internal clock may be set using the
FREQUENCY, STEP, and CLOCK section up/down keys. First select a step size.
Then adjust current frequency using this step size. The complete setup procedure
follows:
1. Select a step size. Do this by pressing the STEP key one or more times until
the underscore in the frequency field is under the desired digit. Note that the
underscore moves right one digit for each key press. The selected digit
indicates step size. For example if the current frequency is 622.950 MHz, and
the underscore is under the "5" , then current step size is 10 kHz. Or, if the
underscore is under the "9" then the current step size is 100 kHz, etc.
2. Press the FREQUENCY key. Verify that the FREQUENCY key LED turns
on.
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3. Press the clock section up/down keys to increment or decrement the current
frequency using the previously selected step size. Note that the underscore
position indicates a step size, not which digit will be edited. For example if
displayed frequency is 622.950, and the cursor is under the "9", then step size
is 100 kHz and pressing the up (• ) key one time will change frequency to
623.050 MHz.
Saving a Frequency
You may save the current Generator frequency into one of 10 frequency memory
locations as follows:
1. Press the clock SAVE key. Verify that the SAVE LED is flashing.
2. Press the clock section up/down keys to select the desired memory location .
Note that frequency memory location is displayed in the bottom left field of
the display as FREQ x, where x = 0, 1, ..., 9.
3. Then press SAVE a second time to save the current frequency into this
location. Verify that the clock SAVE key LED turns off.
Recalling a Frequency
You can recall a previously saved frequency as follows:
1. Press the clock RECALL key and verify that the RECALL LED turns on.
2. Press the clock up/down keys until the display shows the desired frequency
(top left) and frequency memory location (bottom left).
NOTE: The displayed frequency becomes the current frequency immediately.
That is, you do not have to hit RECALL again.
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Data and Clock Outputs
This section explains how to set up the Generator's clock and data outputs as well
as related pattern sync. and clock/4 outputs.
Overview
The OUTPUT section of the Generator front panel contains the instrument's main
NRZ (clock + data) outputs:
DATA
DATA-BAR
CLOCK
CLOCK-BAR
Note: The same term can be expressed three different ways.
= CLOCK BAR
= NOT CLOCK
CLOCK
DATA
= DATA BAR
= NOT DATA
DATA and CLOCK are the non-inverted test pattern outputs of the GB1400
Generator. DATA is a non-return to zero (NRZ) data signal and CLOCK is its
corresponding clock signal. DATA-BAR and CLOCK-BAR are complementary
outputs to DATA and CLOCK respectively. Thus the GB1400 can drive single-
ended or differential inputs.
The amplitude and baseline offset of the CLOCK and DATA outputs are
adjustable. This insures compatibility with a wide range of input circuit designs.
The selected clock amplitude applies to both CLOCK and CLOCK-BAR and the
selected data amplitude applies to both DATA and DATA-BAR.
Similarly the selected clock baseline offsets becomes the bottom (negative peak
voltage) of both the CLOCK and CLOCK-BAR outputs and the selected data
baseline offset becomes the bottom voltage of the DATA and DATA-BAR
outputs.
The nominal waveform and phase relationship of the four output signals is shown
in the figure below. An equivalent circuit model for these four outputs is shown
in the second figure.
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V
top (clock )
CLOCK
Amplitude
(pk -pk )
CLO CK
CLOCK
Bas eline
Offse t
S ame amplitude
a s CLOCK
CLOCK
Sa me offs et
as CLOCK
V
top (da ta)
DATA
DATA
Amplitude
(pk-pk)
DATA
Bas eline
Offse t
V
top
DATA
Sa me amplitude
a s DATA
Same offset
as DATA
Figure 3-1. Nominal Generator Clock and Data Waveforms Showing
Amplitude, Baseline Offset, and V
.
top
Voch = Out high voltage into an open circuit
50 W
50 W
Vh (logic high) DATA
or CLOCK Output
Vhl(logic low) DATA
or CLOCK Output
l = Vocamp/50
Negative Supply
Figure 3-2. Generator Clock and Data Output Equivalent Circuits
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Amplitude and Baseline Offset
The rules governing the setup of clock and data amplitude and baseline offset are
as follows:
RULE 1: When terminated by 50 Ohms to ground, the amplitude adjustment
range of clock and data outputs is 0 to 2 V peak-to-peak. However, the absolute
voltage of the pulse top cannot exceed +2.0 VDC, that is:
V
+ V £ 2.0 VDC
offset
amplitude p-p
RULE 2: When left unterminated (termination impedance > 2 kW) the amplitude
adjustment range of clock and data outputs is 0 to 4 V peak-to-peak with a pulse
top limit of +4.0 VDC, that is:
V
+ V £ 4.0 VDC
offset
amplitude p-p
RULE 3: Displayed amplitude and baseline offset are calibrated for a
termination of 50 Ohms to ground. Any variation of termination impedance or
voltage will cause actual amplitude and offset to differ from the values shown in
the Generator display.
These rules are summarized in the table below.
Table 3-2. Output Setup Rules vs. Termination Impedance
Termination
Amplitude Limit
(V p-p)
Pulse Top
Limit (VDC)
+2.0
Actual
Amplitude
as displayed
Actual Baseline Offset
(VDC)
as displayed
0 - 2
50 W to ground
0 - 2
0 - 2
0 - 4
+2.0
+2.0
+4.0
as displayed
as displayed
2 x displayed
displayed value - 1.0 V
unspecified
as displayed
50 W to -2 VDC
AC (50 W to AC)
Open Circuit
Note: With PECL option installed, the pulse top limits are increased to 2.8 (50W)
and +5.6 (open circuit).
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The following controls are used to set clock and data output amplitude and
baseline offset:
CLOCK:
DATA:
AMPLITUDE (• , ¯ ):
BASELINE OFFSET (• , ¯ ):
Note that when the CLOCK key is pressed, its LED turns on and the display
shows clock output amplitude and offset. Similarly, when the DATA key is
pressed, its LED will turn on and the display shows data output amplitude and
offset. The general procedure for setting data and clock output amplitude and
baseline offset is shown below.
1. Press DATA. The display will show data output amplitude and offset.
2. Press the BASELINE OFFSET up/down keys to set the desired data signal
baseline offset.
3. Then press the AMPLITUDE up/down keys to set the desired data signal
amplitude.
4. Press CLOCK. The display will now show clock output amplitude and offset.
5. Press the BASELINE OFFSET up/down keys to set the desired clock signal
baseline offset.
6. Then press the AMPLITUDE up/down keys to set the desired clock signal
amplitude.
Logically Inverting Output Data (D-INV)
The INVERT DATA key may be used to logically invert the output data pattern,
that is change all 1s to 0s and 0s to 1s. If the INVERT DATA LED is off, then
the output data pattern is not inverted. However if the INVERT DATA LED is
on, the output data pattern is logically inverted. You can toggle the INVERT
DATA function on and off by pressing the INVERT DATA key. Note that
logically inverting the output pattern is the same as swapping the connections to
the DATA and DATA-BAR outputs.
To toggle output data inversion on or off, press the INVERT DATA key.
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Single-ended or Differential Operation
DATA-BAR and CLOCK-BAR are complimentary outputs to DATA and
CLOCK respectively. Therefore, to drive a single-ended clock or data input
simply connect appropriate true output (CLOCK or DATA) while terminating its
compliment (CLOCK-BAR or DATA-BAR) with 50 Ohms to ground. Or, to
drive a differential clock or data input, connect the appropriate true output
(CLOCK or DATA) to the non-inverting input and the complimentary output
(CLOCK-BAR or DATA-BAR) to the inverting input. No other setup is required
to configure the Generator for singled-ended or differential operation.
Procedure for Single-ended Operation (TX only)
1. For singled-ended operation, connect Generator CLOCK and DATA outputs
to singled-ended inputs on the DUT.
2. Terminate the CLOCK-BAR and DATA-BAR outputs with 50 Ohms to
ground.
Procedure for Differential Operation (TX only)
1. Connect CLOCK and CLOCK-BAR outputs of the Generator to the true and
complimentary clock inputs on the DUT.
2. Connect DATA and DATA-BAR outputs of the Generator to the true and
complimentary data inputs on the DUT.
Pattern Sync and CLOCK/4 Outputs
The OUTPUT section of the Generator front panel contains two additional
outputs that may be useful when observing the Generator output with an
oscilloscope. The first is the Pattern Sync or output which generates one pulse
per pattern frame. This signal may be used to trigger an oscilloscope at the
beginning of the output data pattern. The second is the CLOCK/4 output, which
is a clock signal at one quarter the frequency of CLOCK. This signal is
particularly useful when viewing the output of the Generator using an
oscilloscope that doesn't have sufficient bandwidth to trigger on the CLOCK
signal.
Both the Pattern Sync and CLOCK/4 outputs have a fixed amplitude of 200 mV
pk-pk, centered around ground, when terminated by 50 Ohms to ground. The
phase relationship of CLOCK/4 and CLOCK is also fixed, with the nominal
location of CLOCK/4 transitions occurring on the falling edge of CLOCK.
The width and location of the Pattern Sync pulse depends on which pattern type
is currently active. For PRBS patterns, the Pattern Sync pulse has a width equal
to one bit time slot, at a fixed position not adjustable by the user. For short-
WORD patterns (1-Mbit Option not installed) the Pattern Sync waveform is a
nominal square wave that is high during the first byte of a 16-bit WORD, and
low for the second. For long-WORD patterns (1-Mbit Option installed), the
Pattern Sync pulse is one byte wide that occurs at the beginning of the frame.
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Error Injection
The GB1400 Generator can inject bit errors, also known as logic errors, into the
output data pattern. One use of error generation is to self-test the GB1400
Generator/Analyzer system. Or, when generating WORD patterns containing
simulated framed signals, for example a SONET signal, error generation can be
used to determine the ability of the terminal under test to detect errors or to stay
in-frame in the presence of high error rates.
-n
The available internal error injection rates are 10 , where n = 7, 6, 5, 4, or 3. In
-7
other WORDs, injected BER can be set to integer powers of 10 from 10 to
-3
10 . Using the external error inject mode, errors can be injected at any rate up to
-3
10 . There is no lower limit on external error injection BER.
Selecting an Error Inject Mode
The controls that determine the error injection mode of the Generator are:
RATE (key)
SINGLE (key)
When the LED on the RATE key is off, the Generator is in the single error inject
mode. In this mode, no errors are generated except when the SINGLE error key
is pressed. That is, each press of the SINGLE key will cause a single, isolated bit
error to be injected. However, when the RATE key is on, the instrument is either
generating an error rate internally, or under external error generation control.
You can determine which by observing the bottom, middle field of the display.
If an error rate is displayed (e.g. ERR 1E-09) then the Generator is in the internal
error inject mode. If the message EXT ERR is displayed, then the external error
inject mode has been selected indicating that the signal appearing at the rear-
panel EXTERNAL ERROR INJECT input will control error injection rate. One
error will be generated for each negative-to-positive transition in this signal. In
all other error inject modes, the signal appearing at this input will be ignored.
NOTE: In all error injection modes, the ERROR LED will flash each time an
error is injected.
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Procedure to Control Error Injection Mode
1. Press the RATE key one or more times to select the desired error injection
mode. Note that the LED in the RATE key will turn on except when mode is
set to ERR OFF. Available selections are:
ERR OFF: Single error injection.
-7
-7
ERR 1E : Generate errors at rate of 10 .
-6
-6
ERR 1E : Generate errors at rate of 10 .
-5 -5
ERR 1E : Generate errors at rate of 10 .
-4 -4
ERR 1E : Generate errors at rate of 10 .
-3
-3
ERR 1E : Generate errors at rate of 10 .
ERR EXT: External error inject mode.
2. Once you have selected an internal error rate, or the external mode, you can
turn this error rate off and on by alternately pressing the SINGLE key and
RATE key. Do not press the RATE key two or more times in a row unless
you want to change the current error injection mode. However, while the
current error rate is off, you can press the SINGLE key as many times as you
wish to inject single errors.
3. To return to the single injection mode, press RATE one or more times until
ERR OFF is selected.
ERROR INJECT Input
The ERROR INJECT input is an SMA (female) connector located on the rear-
panel of the Generator. When the error injection mode is set to ERR EXT, one bit
error will be generated for each rising edge in the signal applied to this input.
Setup - The ERROR INJECT is a 50 Ohm, ECL input. No hardware setup is
required.
Data Inhibit - The DATA INHIBIT input is located on the rear-panel of the
Analyzer. A signal applied to this input may be used to gate off and on the
Generator DATA output signal. The logic of the DATA INHIBIT function is
shown in the following table. The DATA INHIBIT function is not bit or frame
synchronized with the DATA output signal. Therefore, the gating action caused
by the DATA INHIBIT input may occur anywhere within a DATA output bit
time slot and anywhere within a pattern frame. DATA INHIBIT is a standard 50
Ohm ECL input and does not require any threshold or delay setup.
Table 3-3. Data Inhibit Logic
Logic Level Applied to
DATA INHIBIT INPUT
OPEN or LOW
Action
DATA output operates normally.
HIGH
DATA output is disabled, that is forced LOW.
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Analyzer (RX) Functions
This section explains how to enable or disable Analyzer automatic
synchronization functions. It further shows how to manually set Analyzer input
parameters and error detection functions, and how to start tests, view results, and
print results. The section also defines all results calculated by the Analyzer.
Automatic Setup Functions (SYNC )
This section explains how to use the following "SYNC" controls and indicator in
the ERROR DETECTION section:
AUTO SEARCH key.
DISABLE key.
LOCK indicator.
AUTO SEARCH Key
The AUTO SEARCH key is used to enable or disable the auto-search feature.
When auto-search is enabled, the Analyzer will automatically attempt to set the
following parameters each time pattern synchronization is lost:
1. clock and data input threshold,
2. data input delay,
3. PRBS pattern,
4. pattern polarity, and
5. pattern alignment.
In addition, auto-search will clear (turn off) the BIT and PHASE history
indicators once pattern sync. is regained. Thus, AUTO SEARCH can greatly
simplify Analyzer setup and operation, especially when the input clock and data
phase relationship and amplitudes are not known.
DISABLE Key
The DISABLE key is used to disable automatic pattern realignment. When
automatic pattern realignment is enabled (DISABLE off) the Analyzer will
attempt to resynchronize its pattern detector each time BER goes above the
pattern synchronization threshold by looking for a new pattern alignment. A
change of pattern alignment will occur, for example, if a buffer over flows or
under flows in the DUT. A change of pattern alignment will also normally occur
if the CLOCK input to the Analyzer is momentarily disconnected.
On the other hand, with pattern realignment disabled (DISABLE on), the
Analyzer will not attempt to find a new pattern alignment—even if BER goes
above the synchronization threshold—until the start of a new test interval. This
allows the analyzer to measure BER and count errors on signals with very high
error rates.
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LOCK Indicator and Actions Taken by the Analyzer if
Synchronization (Lock) is Lost
The LOCK LED indicates whether or not BER is above or below the current
synchronization threshold. The LOCK indicator will turn on while BER is below
the current synchronization threshold, and off while BER is above this threshold.
The setup actions taken by the Analyzer when BER crosses the synchronization
threshold will depend on the state of the AUTO SEARCH and DISABLE keys,
as shown in the table below.
Table 3-4. Actions Taken by Analyzer when Synchronization is Lost
AUTO SEARCH
DISABLE
Action when synchronization is lost (LOCK LED turns off)
Analyzer will attempt to find new pattern alignment, input level, input
delay, PRBS pattern and pattern polarity
on
off
off
off
off
on
Analyzer will attempt to find new pattern alignment.
No setup change—Analyzer will continue to measure BER and count
errors.
on
on
(this combination not allowed)
AUTO SEARCH With PRBS Patterns
When using a PRBS pattern you can enable the AUTO SEARCH feature as
follows:
1. Set up the Generator to transmit a PRBS pattern.
2. Set up the Analyzer as follows:
EXT (ref. data input control), off
SYNC DISABLE, off
AUTO SEARCH, on
After you perform this procedure, the auto-search feature will be enabled and the
instrument will immediately attempt to re-synchronize with the received test
signal. Once lock is achieved—that is once BER goes below the synchronization
threshold—the BIT and PHASE history indicators will be cleared (turned off)
and all current error counts will be reset to zero. The SYNC LOSS indicator will
remain on, however, until cleared by the user.
NOTE: The AUTO SEARCH feature will work over a wide range of conditions.
Therefore if you have set up the Generator to generate a standard PRBS, enabled
the AUTO SEARCH feature on the Analyzer, but the Analyzer LOCK LED still
fails to turn on, then it is likely that a problem exists in the device under test or
your patch cord connections.
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AUTO SEARCH with "Non-PRBS" Patterns
In cases where you need to use a WORD or other type pattern for testing, you
can still use AUTO SEARCH to set DATA and CLOCK threshold, and DATA
input delay and threshold as follows:
1. Set up the Generator to transmit a PRBS pattern.
2. Enable Analyzer AUTO SEARCH as follows:
EXT (ref. data input control), off
SYNC DISABLE, off
AUTO SEARCH, on
3. After the Analyzer LOCK LED turns on, disable AUTO SEARCH by
pressing the AUTO SEARCH key. Verify that the LED in the AUTO
SEARCH key turns off.
4. Change the pattern setup of the Generator and Analyzer as desired. For
example, to perform a test using a WORD pattern stored in memory: press
the Analyzer pattern RECALL key and up/down keys to select the WORD
pattern. Repeat these steps on the Generator to select the same WORD
pattern. At this point the SYNC LOCK LED should turn on again indicating
that the Analyzer has regained synchronization. You may now start a new
test interval by clearing previous results (PRESS ERROR DETECTION
CLEAR key) and history indicators (PRESS HISTORY CLEAR key).
How to DISABLE Automatic Pattern Resynchronization
The pattern resynchronization disable feature is turned on or off as follows:
Press the DISABLE key to toggle automatic pattern resynchronization on or off.
When the DISABLE LED is on, pattern resynchronization is disabled. When the
DISABLE LED is off, pattern resynchronization is enabled.
Relationship between AUTO SEARCH and DISABLE
Turning AUTO SEARCH on automatically turns DISABLE off. Similarly,
turning DISABLE on automatically turns AUTO SEARCH off. That is, AUTO
SEARCH and DISABLE cannot be on at the same time. However you may turn
both functions off. There are, therefore, three possible levels of Analyzer
synchronization:
1. AUTO SEARCH on: This is the most automated mode.
2. AUTO SEARCH off and DISABLE off: This is a partially automated mode
with AUTO SEARCH functions disabled but auto-pattern resynchronization
still enabled.
3. DISABLE on: This is the "fully manual" mode in which all AUTO SEARCH
functions and the auto-pattern resynchronization function, are disabled.
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Synchronization (LOCK) Threshold
The current synchronization threshold depends on pattern, and the setup of the
SYNC Menu, as summarized in the table below:
Table 3-5. Synchronization Threshold
Pattern Type
Threshold
How to Set
PRBS
1,024 errors in 4,096 bits
(BER = 2.5 E-01)
128 errors in 4,096 bits
(BER = 3.1 E-02)
Fixed
Fixed
All WORD patterns (up to 16
bits) when 1-Mbit Option not
installed.
All WORD, mark density, or
other ROM patterns with 1-Mbit window of x bits. Nine BER levels
Option installed. available:
Based on 256 errors in a rolling
Use SYNC Menu to select
a synchronization level from
1 to 9.
1:
2:
3:
4:
5:
6:
7:
8:
9:
3.1 E-02
7.8 E-03
1.9 E-04
9.7E-04
4.8 E-04
2.4 E-04
1.2 E-04
6.1 E-05
3.0 E-05
You can change the synchronization threshold for (long) WORD, mark density,
and ROM patterns using the SYNC Menu as follows:
Procedure to Set SYNC Threshold
1. Press the F1 key to enter the Menu system.
2. Press F4 key to enter the WORD submenu.
3. Press the F1 key (MORE) until the SYNC option appears.
4. Press F2 (SYNC).
5. Use the pattern up/down keys to select a synchronization threshold level
from 1 to 9.
6. When done, press F4 to enter your choice.
7. Press F1 multiple times until you have exited the Menu system.
NOTE: See later in this chapter for a further explanation of the SYNC Menu.
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Clock, Data, and Reference Data Inputs
This section explains how to set up Analyzer clock, data, and reference data
inputs using front panel controls and Menus.
Overview
The Analyzer CLOCK, DATA, and REF DATA inputs are designed to
accommodate a wide range of output logic levels and circuit designs. An
equivalent circuit diagram of the Analyzer input section is shown in the
following figure.
Input
Comp
W
50
-2Vdc
AC
GND
Figure 3-3. Analyzer Clock and Data Input Circuits
Input Parameters
The following input parameters may be set manually by the user or automatically
by the AUTO SEARCH function:
Decision threshold (DATA, and REF DATA)
Delay (DATA and REF DATA)
Inverted or non-inverted data (DATA).
In addition, there are termination parameters that can be selected only by the
user:
Termination (CLOCK, DATA, and REF DATA)
Note that user or manual control functions may be executed locally, via front
panel controls or Menus, or remotely via the instrument's RS-232 or GPIB ports.
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Controls
The INPUT section controls that are used to set up input parameters are:
DELAY key
V-TERM key
V-THRESH key
INPUT (• , ¯ ) Keys
D-INV key
In addition, the state of the F2 and F3 function keys determines the action of the
INPUT up/down keys as shown in the table below. Note that this function of the
F2 and F3 keys does not apply while the Analyzer is in the Menu mode.
Table 3-6. How F2 and F3 Determine Which Input Can be Set Up
F2
F3
Input that can be adjusted
using (• ,¯ ) Keys
off
on
off
on
off
off
on
on
DATA
CLOCK
REF DATA
not allowed
Use of the Display
The Analyzer display will normally show the currently selected delay or
termination parameter in the bottom left field and the currently selected voltage
threshold parameter in the bottom right field. In addition the bottom middle field
will show whether or not input data inversion is enabled. Specifically, if the
INVERT DATA key is on, then the message INV will appear after the name of
the current pattern, for example PN 23 INV.
Input Data Delay
Up to 4 ns of delay can be added to the DATA and REF DATA inputs to adjust
their phase alignment with the input clock signal. A different amount of delay
may be added to each of these inputs so that the Analyzer can accommodate
different phase relationships between DATA, REF DATA, and CLOCK.
Procedure to Add Delay
1. Select either the DATA or REF DATA inputs using the F2 and F3 keys.
Enable F3 to select REF Data. Disable F2 and F3 to select DATA.
2. Press the DELAY key. Verify that its LED turns on.
3. Press the input up/down keys while observing the amount of added delay in
the bottom left field of the display. Delay may be set in the range 0 to 4 ns, in
5 pS steps for DATA or in 100 pS steps for REF DATA.
The delay value shown in the display is in effect immediately. In other WORDs,
delay is changed each time you press the up or down key. Note that delay is an
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AUTO SEARCH parameter. Therefore, you should normally turn off AUTO
SEARCH if you want to fix delay at a specific value.
Input Termination
The input termination can be independently selected for the CLOCK, DATA, and
REF DATA inputs. Note that the termination selected for CLOCK and DATA
also applies to the CLOCK-BAR and DATA-BAR inputs. Available input
terminations are shown in table below.
Table 3-7. Input Terminations for CLOCK, DATA, and REF DATA
Label
GND
- 2 V
AC
Termination
50 Ohms to ground.
50 Ohms to -2 VDC.
50 Ohms, via 0.01 mF capacitor, to ground.
Procedure for Selecting Input Termination
1. Select the DATA, CLOCK, or REF DATA inputs using the F2 and F3 keys.
2. Press the TERM key. Verify that its LED turns on.
3. Press the input up/down keys while observing the selected termination in the
display. Available terminations are: GND, -2V, and AC.
The displayed termination becomes effective immediately. In other words,
termination is changed each time you press the up or down key.
Low-Frequency Effects of AC Termination on Single-ended
Operation
Because the single-ended AC termination is AC-coupled to ground, input
impedance will deviate from the nominal 50 Ohm value at low frequencies. As a
practical matter, for any PRBS pattern analyzed by the GB1400, frequency
effects will not be noticed until the peak energy frequency is less than about 10
MHz, which for PRBS patterns will occur only when bit rate is less than about 20
Mb/s. However, for WORD patterns with long strings of contiguous zeros,
effects may be noticed at higher bit rates.
Note that when the AC termination is used with differential operation, the input
termination is not "AC-coupled". Therefore, the above low-frequency limit on
use of the AC termination does not apply when operating the CLOCK or DATA
inputs in the differential mode. Specifically, when the Analyzer clock or data
inputs are set up for differential operation, the AC termination may be used over
the entire bit rate operating range of the Analyzer.
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Input Decision Threshold
The input decision thresholds of the DATA, and REF DATA inputs can be
independently adjusted. However, it is important to note that input threshold
adjustment applies only for single-ended operation. When operating Analyzer
data inputs in the differential mode, their input decision threshold effectively
becomes the average of the positive peak and negative peak voltage levels and is
not adjustable by the user.
Procedure to Adjust (Single-ended) Input Decision Threshold:
1. Verify that the selected input is set up for singled-ended operation. For
DATA operation, connect a cable from rear panel threshold to front NOT-
DATA (DATA-BAR) input.
2. Select either the DATA, CLOCK, or REF DATA input using the F2 and F3
keys.
3. Press the THRESH key. Verify that its LED turns on.
4. Press the input up/down keys while observing selected threshold value in the
bottom, right field of the display. Decision threshold setup range is a function
of input termination as shown in table below.
Table 3-8. Input Threshold Range as a Function of Termination
Selected Termination
Threshold Setup Range
- 1.5 to + 1.0 VDC, 50 mV steps
- 2.5 to + 0.0 VDC, 50 mV steps
- 1.5 to + 1.0 VDC, 50 mV steps
GND
- 2 V
AC
The displayed threshold takes effect immediately. In other WORDs, threshold is
incremented or decremented each time you press the up or down key. Note that
threshold is an AUTO SEARCH parameter. So be sure turn off AUTO SEARCH
if you want to fix delay at a specific value.
Logically Inverting Input Data
The INPUT section INVERT key may be used to logically invert the input data
pattern, that is change all 1s to 0s and 0s to 1s. If the INVERT key is off, then the
input data pattern is not inverted. However if the INVERT key is on, the input
data pattern is logically inverted. You can toggle input data inversion on or off by
pressing the INVERT DATA key. Note that logically inverting the input pattern
is equivalent to swapping the connections to the DATA and DATA-BAR inputs.
To toggle input data inversion on or off, press the INVERT key.
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Singled-ended or Differential Operation
Analyzer clock and data inputs can be operated in a singled-ended or differential
mode. Differential operation provides greater immunity to ground noise and
EMI. Note that threshold setup applies to the clock and data inputs only when
they are operated in the singled-ended mode. When the clock or data input is
operated in the differential mode, its input threshold effectively becomes the
average of the positive peak and negative peak voltage of the received true and
complement signals.
Procedure to Configure CLOCK or DATA Inputs for Single-Ended
Operation
1. Connect Clock signal to CLOCK input.
2. Connect Data signal to DATA input.
3. Connect cable from rear panel DATA THRESHOLD output to front panel
DATA BAR input.
Selecting the Reference Data Mode
In most testing applications, the Analyzer is set up to compare the received data
pattern with a data pattern generated internally by the Analyzer. However you
may also set up the Analyzer to compare two externally generated patterns. This
makes it possible to analyze framed or proprietary signals that cannot easily be
simulated as long WORD patterns.
To configure the Analyzer for reference data testing, the primary or test signal
must be connected to the Analyzer data input (which may be set up for singled-
ended or differential operation) while the reference signal is connected to the
REF DATA input. Then the Reference Data mode must be selected using the
EXT key. Note that the reference signal must be generated by a singled-ended
output.
Procedure for Selecting the Reference Data Mode
1. Connect a test signal to the Analyzer data input and a reference signal to the
REF input.
2. Press the Analyzer EXT key to toggle the reference mode on. Verify that the
EXT key turns on.
3. To de-select the reference mode, press the EXT key again. Verify that the
EXT key turns off.
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Monitor Outputs
The MONITOR CLOCK and DATA outputs are provided so that you can
monitor the test signal as seen by the Analyzer. This allows you to attach an error
logging device, for example, to record the exact times that errors occur. Or, you
may attach another type of instrument to make specialized calculations.
MONITOR DATA is an NRZ output signal with the same bit sequence as that
recovered by the Analyzer front end circuit. MONITOR CLOCK is the
corresponding clock signal. Because the MONITOR output is a regenerated
version of the received test signal, bit errors reported by the Analyzer—due to
noise on the received data (or clock) signals—will be present in the MONITOR
DATA output bit sequence.
Output Setup
All three MONITOR ports (CLOCK, DATA, and Pattern Sync) are 50 Ohm,
single-ended outputs.
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Error Detection Set Up
Overview
The GB1400 Analyzer calculates error results using three different methods:
Window, Test, and Totalize. These three methods are independent of each other
and can operate simultaneously. Window results are used to view current or
"real-time" performance. Totalize results are generally used to view performance
over long intervals. Test results are used to measure error performance over
specified time intervals.
Two results are calculated for all three methods:
BER
Bit Errors
In addition, Test results include the following network performance parameters
and event counts:
Test seconds
Total bits monitored
Errored seconds
Severely errored seconds
Unavailable seconds
Threshold errored seconds
Error-free seconds
Degraded minutes
Signal loss seconds
Pattern Synchronization loss seconds
Phase error seconds
For explanations of these results see Result Definitions later in this chapter.
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How TOTALIZE Results are Measured
Totalize results are measured continuously by the Analyzer. Totalize results can
be cleared by the user (by pressing the CLEAR key when Totalize results are
displayed). However, Totalize result accumulation is a continuous background
process of the Analyzer and cannot be suspended by the user. The Totalize
measurement process is illustrated in the figure below.
CLEAR
Untimed
Measurement Interval
TOTALIZE Process is continuous,
but results may be cleared by the
operator at any time.
Figure 3-4. The TOTALIZE Measurement Process
How WINDOW Results Are Measured
Window Mode results are calculated over a sliding window whose length is
defined by the user. Window results can be cleared at any time by pressing the
CLEAR key when Window Mode results are displayed. But as in the case of
Totalize results, the Window measurement process cannot be suspended by the
user.
Window results may be thought of as a series of snapshots of the received signal
performance. Each snapshot indicates BER and total bit errors over the most
recent interval T, where T is the value of the Window length set by the user. The
amount of "slide" between snapshots is effectively determined by the display
update rate which is about five times per second. Therefore the Window slide
between display updates is about 200 ms. Note that End-of-Window reports are
generated once per second so the effective window slide in printed results is one
second. The Window measurement process is illustrated in following figure.
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CLEAR
WINDOW interval "W" is set in terms
of bits or time in using WINDOW menu.
W
W
W
Slip time "S" is effectively 200 ms in display
or 1 sec. in End-of-Window reports
S
W
W
Figure 3-5. The WINDOW Measurement Process
How TEST Results Are Measured
Unlike Totalize and Window results, the accumulation of Test results can be
started or stopped by pressing the CLEAR key. That is, the CLEAR key in effect
becomes a test start/stop key. While a test is "stopped", all current Test results are
frozen. When the CLEAR key is pressed to start a new test, all current Test
results are saved as previous Test results before current result registers are
cleared.
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As shown in the next figure, Test results may be calculated using one of three
timing modes: Timed, Untimed, or Repeat.
TEST Measurement Process
CLEAR
Untimed
Measurement Interval
Untimed TEST Process:
Intervals started and
stopped manually by operator.
TEST interval "T" set in terms of
time (hrs:min:sec) in TEST menu.
CLEAR
CLEAR
CLEAR
CLEAR
Timed TEST Process:
Interv als started by
operator, stopped auto-
matically at end of interval T.
T
T
T
T
Repeat Timed TEST Process:
Process started by operator,
intervals of length T stopped
and re-s tarted automatically.
T
T
T
T
Figure 3-6. The TEST Measurement Process
Timed Tests. When the Timed mode is selected, the Analyzer will automatically
stop accumulating Test results after the test interval (specified by the user) has
elapsed. All Test results will be frozen until the CLEAR key is pressed to begin a
new test.
Repeat (Timed) Tests. When the Repeat mode is selected, the Analyzer will
automatically stop and then restart a test after a user specified test length has
elapsed. This process will continue until the user presses the CLEAR key to
manually stop Test result accumulation.
Untimed Tests. When the Untimed mode is selected, the Analyzer will continue
to collect Test results until the CLEAR key is pressed. At this point Test results
will remain frozen until the CLEAR key is pressed again to start a new test.
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Display Mode: Totalize, Window, or Test
When the Analyzer is not in the Menu mode, you can select a display mode using
the SELECT DISPLAY key. The display mode determines which BER and Bit
Error results are shown in the main display. BER results are shown in the top,
middle field of the display, while Bit Error results are shown in the top right
field. Display mode also determines which results will be cleared when you press
the ERROR DETECTION CLEAR key.
Procedure to Select a Results Display Mode
Press the DISPLAY SELECT key to select a different display mode.
Selections are: Totalize , Window, or Test
The selected display mode will be indicated by the character in front of the BER
result, as explained in the table below. Note that there are three possible Test
display mode characters (T, U, and R) which further indicate which Test timing
mode (Timed, Untimed, or Repeat) has been set up. Note that MODE is a
parameter in the TEST Menu.
Table 3-9. How to Tell Which Display Mode is Active
Character In Front of BER Result
Indicated Result Display Mode
no character (blank)
Window
Totalize
the infinity symbol (¥)
T, U, or R
Test:
T = Timed mode.
U = Untimed mode
R = Repeat mode
Clearing Results and Starting Tests
To do this:
1. Press DISPLAY SELECT until the Totalize Mode results are displayed
(infinity character in front of the BER result).
2. Press the CLEAR key in the ERROR DETECTION section to clear Totalize
BER and Bit Error results.
Totalize Process Set Up
The Totalize measurement process is active all the time and requires no explicit
setup by the operator.
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Window Process Set Up
The Window measurement process may be configured using the four parameters
in the WINDOW Menu:
MODE: Defines window length in terms of "bits" or "seconds".
BITS: Window length in bits.
SECOND: Window length in terms of hours, minutes, and seconds.
REPORT: Turns end-of-window reports on or off.
If you want to measure Window results, you must set the MODE parameter, and
depending on your MODE selection, either the BITS or SECOND parameter. In
addition, if you want to generate end-of-window reports you must also set the
REPORT parameter to on.
Procedure
1.
2.
3.
a.
b.
4.
5.
Press F1 to enter the Menu system.
Select the WINDOW Menu (F3).
Within the WINDOW Menu, set up:
MODE (F2) and
either BITS (F3) or SECOND (F4).
Press MORE (F1) to see the next page of the WINDOW Menu.
If you are using a printer, set the REPORT parameter (F2) to on or off as
required.
6.
When WINDOW Menu setup is complete, press F1 multiple times to exit
the Menu system.
See later in the this chapter for more information on setting up the WINDOW
Menu.
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Test Process Set Up
The TEST Menu contains the following six selections:
LENGTH: Test length: hours, minutes, seconds.
MODE: Test timing mode: Timed, Untimed, or Repeat.
REPORT: Test reporting mode: None, Print On Error, or Both.
THRESH: Threshold for the TES (threshold errored second) result.
SQUEL: On Error report squelch after 10 consecutive seconds: yes or no.
PRINT: Use this function to print current Test results immediately.
If you want to collect TEST results, you must set LENGTH and MODE before
you begin a test. And if you are using a printer you should set the REPORT
parameter as desired. Note that On Error reports can generate a lot of paper, so
select On Error or Both with caution. Setup of the other parameters in the TEST
Menu are optional.
Procedure
1.
2.
3.
a.
b.
4.
5.
Press F1 to access the Menu system.
Select the TEST Menu (F2).
Within the TEST Menu, set up:
LENGTH (F2) and
MODE (F3).
And, if you are using a printer, set up the REPORT parameter (F4).
Press MORE (F1) to see the next page of the TEST Menu. Review the
setup of the THRES (F2) and SQUEL (F3) parameters. Change if
necessary.
NOTE: Setting SQUEL (squelch) to ON is recommended.
6. Press the F1 key multiple times to exit the Menu system.
See later in this chapter for more information of setting up the TEST Menu.
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Viewing Results
BER and bit error results are shown in the normal display mode. However to
view the complete list of Test results, you must use the TEST Menu VIEW-CUR
or VIEW-PRE functions.
BER and Bit Errors
The Analyzer calculates BER and bit errors using all three measurement methods
(Totalize, Window, and Test). The current display mode determines which
BER/bit error result pair is shown in the display. Note that BER is shown in the
top, middle field while the bit error result is shown in the top, right field.
Procedure to View Desired BER and Bit Error Results
Press the DISPLAY SELECT key to select the appropriate display mode.
As noted earlier, the character in front of the BER result will indicate the current
display mode. The infinity symbol (¥ ) indicates Totalize; a blank character
indicates Window; and the T, U, or R characters indicate Test results which have
been measured using the timed, untimed, or repeat timing modes respectively.
All Other Results (Test Process only)
To view the complete set of Test results, select the VIEW-CUR or VIEW-PRE
functions from the TEST Menu. VIEW-CUR will show partial results if a timed
test is in progress, or results from the last completed test. VIEW-PRE will show
results saved in the "previous" test registers. These results are over-written with
the contents of the current registers each time a test is completed.
Procedure
1.
2.
3.
4.
Press F1 to enter the Menu system.
Select the TEST Menu (F2).
Press MORE (F1) twice to view the third page of the TEST Menu.
Select either VIEW-CUR or VIEW-PRE to view all current or previous
Test results respectively. Once inside either the VIEW-CUR or VIEW-
PRE function, use the pattern up/down keys to scroll through the results
list.
5.
When done, press F1 multiple times to exit the Menu system.
See later in this chapter for more information on the TEST Menu. Also see
Measurement Definitions , later in this chapter.
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Printing Results (Reports)
A serial or parallel printer may be connected to the Analyzer's RS-232-C or
PRINTER ports respectively. Note that you cannot connect a GPIB printer
directly to the GPIB port; but you may "print" results to a GPIB controller, which
can store reports for later viewing or printing.
Basic Report Setup Procedure
The following initial setup procedure must be performed in order to generate any
type of Analyzer report.
1.
Connect your printer to the Analyzer RS-232 or PRINTER ports as
appropriate. (See Chapter 6 for details).
2.
3.
4.
Press F1 to enter the Menu system.
Select MORE (F1) to view the second page of the main Menu.
Set up the appropriate hardware port as follows:
a.
If you are using a serial printer, select RS232 (F2) to set up the
serial port.
b.
If you are "printing" to a GPIB controller, select GPIB (F3) to set
up the GPIB port
NOTE: The Analyzer PRINTER port is a standard PC-type parallel port which
requires no hardware setup.
5.
Next, select the PRINT parameter (F4).
a.
b.
Set the PORT parameter to Parallel, GPIB, or Serial.
Set the ON/OFF parameter to ON to enable reports.
NOTE: The PRINT ON/OFF parameter must be set to ON to print any type of
report.
6.
When you have completed all desired setup changes, press F1 multiple
times to exit the Menu system.
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Analyzer Setup Report
Press the F4 key at any time to print an immediate report listing the current setup
of the Analyzer. This function is not available while the Analyzer is in the Menu
mode. An example Setup Report is shown below.
Example Analyzer Setup Report
**** Tektronix, Inc. GB-1400 Jun/14/99 02:14:29
AUTO_SET AUTO
DATA_DELAY 1.800E-9
DATA_THRES 0.05
RDATA_DELAY 0.000E-9
RDATA_THRES -1.50
DATA_TERM GND
CLOCK_TERM GND
RDATA_TERM GND
TEST_LENGTH "00:00:30"
TEST_MODE TIMED
TEST_PREV PRE
TEST_REP ON_ERR
TEST_STATE STOP
TEST_SQUELCH OFF
TEST_THRES OFF
WIN_MODE SEC
WIN_PREV CUR
WIN_REP OFF
WIN_BIT_LEN 09
WIN_SEC_LEN "00:00:01"
PRINT_ENABLE ON
PRINT_PORT PARALLEL
AUDIO_VOL 0
AUDIO_RATE 3
PRBS_LENGTH 23
WORD_BITS 16, #HAA, #H55
DATA_PATTERN WORD
DATA_INVERT ON
WORD_MEMORY 0, 16, #HAA, #H55
WORD_MEMORY 1, 16, #HAA, #H55
WORD_MEMORY 2, 16, #HAA, #H55
WORD_MEMORY 3, 16, #HAA, #H55
WORD_MEMORY 4, 16, #HAA, #H55
WORD_MEMORY 5, 16, #HAA, #H55
WORD_MEMORY 6, 16, #HAA, #H55
WORD_MEMORY 7, 16, #HAA, #H55
WORD_MEMORY 8, 16, #HAA, #H55
WORD_MEMORY 9, 16, #HAA, #H55
VIEW_ANGLE 0
GPIB_ADDRESS 14
GPIB_BUS OFF_BUS
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End-of-Test Reports
When End-of-Test reports are enabled, one End-of-Test report will be generated
each time the end of a Test interval is reached. This can occur automatically,
when timing mode is set to Timed or Repeat, or manually when the user stops an
Untimed test by pressing the CLEAR key. Use the REPORT parameter in the
TEST Menu to enable or disable End-of-Test reports. An example End-of-Test
report is shown below.
Example End-of-Test Report
--------------------------------------------------------------------------------------------------
Tektronix, Inc. GB-1400 TEST SUMMARY
TEST MODE: TIMED
TIME
Jun/14/99 02:42:48
FREQ: 100.0 MHz
ALARMS
ERROR THRES: E-05
PERFORMANCE
START Jun/14/99 02:43:26
STOP Jun/14/99 0s:43:31
ELAPSED 000-00:00:05
SIG LOSS
SYNC LOSS OS SES 0 0.0%
PHASE ERR OS TES 5 100.0%
OS US 0 0.0%
ES 5 100.0%
ERRORS/BITS
TOTAL ERRS 000050000
TOTAL BITS 500002816
EFS 0 0.0%
AVG RATE
CUR RATE
1.0E-04 DM 0 0.0%
1.0E-04
--------------------------------------------------------------------------------------------------
You can set up the Analyzer to generate End-of-Test Reports as follows:
Procedure to Enable or Disable End-of-Test Reports
1.
2.
3.
4.
5.
Complete the basic report setup procedure.
Press F1 to enter the Menu system.
Select the TEST Menu (F2).
Select the REPORT parameter (F4).
You may now either enable End-of-Test reports by selecting END OF
TEST or EOT/ERROR; or disable End-of-Test reports, by selecting
NONE.
6.
7.
Press F4 to lock in you selection.
Press F1 multiple times until you have exited the Menu system.
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End-of-Window Reports
When enabled, an End-of-Window report will occur once every second. The
results of an End-of-Window report are based on a sliding interval T, where T is
set in terms of bits or time (hours:minutes:seconds). Use the REPORT parameter
in the WINDOW Menu to enable or disable End-of-Window reports. Use the
MODE, BITS, and SECOND parameters in the WINDOW Menu to set window
length T. An example End-of-Window report is shown below.
Example End-of-Window Report
Date:
Bits= 5.00E+08
Pattern= AA55
Jun/14/99
Time:
Errs= 5000
Data los= 0
02:42:34.46
Err rate= 1.0E-04
Sync Los= 0
Freq= 100.00 MHz
Phase Err= 0
Procedure to Enable or Disable End-of-Window Reports
1.
2.
3.
4.
5.
6.
7.
Complete the Basic Report Setup Procedure.
Press F1 to enter the Menu system.
Select the WINDOW Menu (F3).
Press F1 to see the second page of the WINDOW Menu.
Select the REPORT parameter (F2).
Set the REPORT parameter to ON. Press F4 to lock in this choice.
Exit the Menu system by pressing F1 multiple times until the normal
display format appears.
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On-Error Reports
When enabled, On-Error reports are generated for each second in which error
rate is above the current THRES threshold. Note that On-Error reports can be
squelched after reports are generated on 10 consecutive seconds, by enabling the
SQUEL feature. This is recommended for unattended operation since On-Error
reports can generate a lot of paper. An example On-Error report is shown below.
Example On-Error Report
-------------------------------------------------------------------------------------------------------------------------
Tektronix, Inc.
GB-1400 TEST START
Jun/14/99 02:42:48
TIME: 02:42:48
TIME: 02:42:49
TIME: 02:42:50
ERRORS: 10000
ERRORS: 10000
ERRORS: 10000
RATE: 1.00e-004
RATE: 1.00e-004
RATE: 1.00e-004
SynLos
-------------------------------------------------------------------------------------------------------------------------
Procedure to Enable On-Error Reports
1.
2.
3.
4.
5.
Complete the basic report setup procedure.
Press F1 to enter the Menu system.
Select the TEST Menu (F2).
Select the REPORT parameter (F4).
You may now either enable or disable End-of-Window reports by setting
the WINDOW REPORT parameter to ON or OFF.
6.
7.
Press F4 to lock in your selection.
`Press F1 multiple times to exit the Menu system.
On-Demand Test Reports
You can generate a test summary report on demand using the PRINT function in
the TEST Menu. While a test is in progress, the PRINT function will generate a
summary report based results from the current test interval. This report will have
the same basic format as an End-of-Test report. If a test is not in progress, the
PRINT function will generate an End-of-Test Report based on previous results,
that is results from the most recently completed test interval.
1.
1.
2.
3.
4.
5.
6.
Procedure to Generate an On-Demand Test Summary Report
Make sure the Basic Report Setup Procedure has been completed.
Press F1 to enter the Menu system.
Select the TEST Menu (F2).
Press F1 to see the second page of the TEST Menu.
Select the PRINT parameter to generate an immediate Test report
Press F1 multiple times to exit the Menu system.
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Result Definitions
The following section defines all results calculated by the Analyzer.
BER and Bit Errors
The following two results are calculated by all three Analyzer measurement
processes (Totalize, Window, and Test):
Bit Errors: The total number of bit (logic) errors counted in the
measurement interval. May be based on Totalize, Window, or Test
measurement intervals.
Bit Error Rate (BER): Also known as "bit error ratio". May be based on
Totalize, Window, or Test measurement intervals. Equals the number of
bit errors divided by the total number of bits in the measurement interval:
BER = TE / TB
where:
TE = total number of bit errors in the interval
TB = total number of bits in the interval
Note that BER results, when included in End-of-Test or Immediate Test Reports,
are identified as follows:
AVE RATE: BER calculated over the entire TEST interval.
CUR RATE: BER calculated over the latest WINDOW interval.
All Other Results (Test Intervals Only)
The following results are calculated over Test intervals only. You can view all
Test results using the VIEW-CUR and VIEW-PRE functions in the TEST Menu.
Or, you can print all Test results at the end of Test intervals or immediately,
using the REPORT or PRINT functions respectively in the TEST Menu.
SIG LOSS: The number of 20 ms intervals in which the Analyzer input
activity detector sees no transitions on the input CLOCK signal for 20
ms.
SYNC LOSS: The number of 20 ms intervals in which pattern
synchronization (lock) is lost.
PHASE ERR: The number of 20 ms intervals in which a phase error
event is detected. The Analyzer will report a phase error when the active
clock edge moves too close to the data waveform transition point, thus
violating the input circuit setup or hold time.
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Errored Seconds (ES): The number of seconds in the measurement
interval containing one or more errors. The GB1400 measures
asynchronous errored seconds—that is one second intervals based on the
instrument's internal clock rather than the detection of an error. Errored
seconds are not counted during unavailable time (see below). However,
the errored second count does include both severely errored seconds and
non-severely errored seconds.
ES = TSE - US
TSE = total seconds in the current measurement interval with
one or more errors.
US = unavailable seconds in the current interval
% Errored Seconds (%ES): Errored seconds as a percentage of the
total number of seconds in the measurement interval:
%ES = ( ES / TS ) * 100%
ES = errored seconds in the measurement interval
TS = total seconds in the measurement interval
Error Free Seconds (EFS): The number of seconds that contain no
errors and are not unavailable.
EFS = (TS - ES - US)
TS = total seconds in the measurement interval
ES = errored seconds in the measurement interval
US = unavailable seconds in the measurement interval
%EFS: Percentage Error-free Seconds. Error-free seconds as a
percentage of the total number of seconds in the measurement interval.
% EFS = ( EFS / TS) * 100%
EFS = error-free seconds in the measurement interval
TS = total seconds in the measurement interval
Severely Errored Seconds (SES): The number of errored seconds in the
measurement interval which BER is greater than or equal to 1E-03,
excluding unavailable seconds. For example, on a 100 Mb/s test signal,
this would include all available, synchronous errored seconds with
100,000 or more errors.
SES = (seconds with BER ³ 1E-03) - US
US = unavailable seconds in the current interval
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TES: Threshold Errored Seconds: The number of seconds in the
measurement interval in which BER exceeds the threshold set by the
THRES parameter in the TEST Menu, minus the number of unavailable
seconds. Available threshold values are 1E-n, where n = 2, 3, ... 16.
TES = (seconds with BER ³ Threshold) - US
US = unavailable seconds in the current interval
Degraded Minutes (DM): The number of 60 second intervals in the
current interval in which the BER exceeds the current test threshold
(THRES).
Percentage Degraded Minutes (%DM): The number of degraded
minutes expressed as a percentage of the total number of minutes in the
measurement interval.
% DM = ( DM / TM) * 100%
DM = degraded minutes in the measurement interval
TM = total minutes in the measurement interval
Unavailable Seconds (US): The number of seconds in unavailable
intervals. Unavailable intervals start upon the detection of 10 contiguous
severely errored seconds (SES), and end upon the detection of 10 non-
severely errored seconds.
Percentage Unavailable Seconds (%US): The number of unavailable
seconds expressed as a percentage of total seconds in the measurement
interval.
% US = ( US / TS) * 100%
US = unavailable seconds in the measurement interval
TS = total seconds in the measurement interval
Error History Indicators
The Analyzer (performance) history indicators are
located in the ERROR HISTORY section of the front
panel. These indicators will latch on when the indicated
event occurs, and can be cleared by the user.
SYNC LOSS
BIT
PHASE
POWER
CLEAR
SYNC LOSS: This indicator will turn on if the LOCK LED turns off;
that is if the BER rises above the current synchronization threshold (See
Synchronization (LOCK) Threshold in Chapter 4)
BIT: Will turn on if a bit error is detected.
PHASE: Will turn on if a phase error is detected. The Analyzer will
report a phase error when the active clock edge moves too close to the
data waveform transition point thus violating the input circuit setup or
hold time.
POWER: Will turn on after a power loss has occurred.
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CLEAR Control
Pressing the CLEAR key will reset all active history indicators. Note that when
you start a test, you must clear test results and history indicators by pressing the
ERROR DETECTION CLEAR and ERROR HISTORY CLEAR keys
respectively.
Audio (Beeper) Function
The Analyzer may be set up to "beep" each time a second is detected in which
BER is above a specified threshold. The AUDIO VOL and RATE controls are
used to configure this function.
Procedure To Set Up the Audio Alert Function
1.
Press the AUDIO RATE up or down keys to increment or decrement the
current audio alert BER threshold. The current value of the AUDIO
RATE will be displayed in the bottom, right field of the display for about
seven seconds after the last key press. Available selections are 1E-x,
where x = 2, 3, ... 16
2.
Press the AUDIO VOL up or down keys to increment or decrement the
current audio alert volume. There are four volume levels. The minimum
value is "OFF". Except when volume is set to the minimum level, a beep
will occur each time you press an AUDIO VOL up or down key to
indicate the current volume.
Analyzer Error Messages
When abnormal input conditions are detected, the Analyzer will display various
error messages to indicate an unusual condition. These are explained below.
NO CLOCK: This message will appear in the frequency field (top, left)
if no activity is detected at the CLOCK input for 20 ms.
NO DATA: This message will appear in the BER field (top, middle) if
no activity is detected at the data (or clock) input for 20 ms.
LOW AMP: May appear when no signal or a low-signal is applied to the
CLOCK or DATA input and AUTO_SEARCH is enabled
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Starting and Stopping Measurements
The following section explains how to start and stop TEST measurements, and
how to initialize or "re-start" WINDOW and TOTALIZE measurements.
The TEST measurement process has two states: started and stopped . In the
started or active state, new "current" results are accumulated while all results
from the previous TEST interval are saved in memory. In the stopped state, all
current results are frozen so that in effect the results from the last two TEST
intervals are saved in memory.
You can tell whether the current TEST process is started or stopped by observing
the TEST character (T, U, or R) in the display. If the displayed TEST character
(in front of the BER result) is blinking, then the TEST process is stopped and
current results are frozen. On the other hand, if the TEST character is not
blinking, that is if it is on steady, then the current TEST process is started and
new results are accumulating.
You can start and stop TEST measurements as follows:
Procedure for Starting the TEST Measurement Process
1.
2.
3
Configure your Analyzer and Generator as desired. In particular, select a
TEST timing mode: Timed, Untimed, or Repeat.
Use the DISPLAY SELECT key to set the display mode to TEST. Verify
that the expected TEST character (T, U, or R) is shown.
If the TEST character is blinking, press the ERROR DETECTION
CLEAR key to stop the TEST process.
3.
At this point you may press the ERROR DETECTION CLEAR key to
start a new TEST process at any time. After pressing CLEAR, verify that
the displayed TEST character is no longer blinking. After starting a new
TEST interval you may also reset the bit, phase, and power history
indicators by pressing the ERROR HISTORY CLEAR key.
Regardless of the current TEST timing mode, you can stop an active TEST
process as follows:
Procedure for Stopping the TEST Process
1.
Use the DISPLAY SELECT key to set the display mode to TEST. Verify
that the expected TEST character (T, U, or R) is shown.
2
Observe the TEST character.
a.
If the character is on steady, then you may stop the current TEST
interval by pressing the ERROR DETECTION CLEAR key.
b.
However, if the character is blinking then the TEST process is
already stopped and you should not press the CLEAR key until
you want to start a new TEST interval.
Note that TEST measurement starting and stopping can be controlled manually
or automatically, depending on the selected timing mode. When the Untimed
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mode is selected, TEST intervals must be started and stopped manually by the
user. When the Timed mode is selected, TEST intervals are started manually, but
stopped automatically after an interval determined by the LENGTH parameter in
the TEST Menu. When the Repeat timing mode is selected, once the TEST
process has been started by the user, new TEST intervals are stopped and then re-
started automatically, at intervals determined by the LENGTH parameter.
However, even when the Repeat mode is selected, the overall TEST process can
controlled by the user, that is started and stopped manually.
Starting New Totalize and Window Measurement Intervals
Unlike the TEST process, the Totalize and Window measurement processes are
continuous background processes that cannot be stopped and started by the user.
However you can clear all current results to start a new measurement interval as
follows:
Procedure for Starting a New Totalize or Window Measurement Interval
1.
2.
Configure your Analyzer and Generator as desired.
Select the desired display mode (Totalize or Window).
At this point you may press the ERROR DETECTION CLEAR key at any time
to zero all current results and start a new measurement interval. After starting a
new TOTALIZE or WINDOW interval you may also reset the bit, phase, and
power history indicators by pressing the ERROR HISTORY CLEAR key.
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Menus
This chapter explains how to use the GB1400 Menu system. It includes basic
rules, an overview of the Generator and Analyzer Menu structures, and a
description of each Menu function.
Functions Performed Using the Menu System
The GB1400 Menu system is used to perform two types of functions: setup and
immediate. Menu setup functions are used to set up instrument parameters such
as test mode (untimed, timed, or repeat), of test duration, and window length.
Setup functions are also used to configure remote ports and to enable or disable
reports. Menu immediate functions are used to view or print results based on the
"test in progress" or the last completed test. Immediate functions are also used to
view the instrument's software version or a list of installed options.
Note that a few Menu functions can also be performed using front panel keys—
for example setting WORD length. However most Menu functions do not have
front panel equivalents.
Menu and Function "Pages"
Once you press the F1 key to enter the Menu system you will see two basic
display or "page" formats: Menus and functions. Menu pages are used to pick a
function or another Menu by pressing one of the function keys (F1 ... F4).
Function pages are used to change one or more setup parameters (setup
functions) or to perform specific actions (immediate functions).
An example setup procedure is presented next to illustrate the use of Menus and
functions. The objectives of this example procedure will be to:
Set TEST length to 30 minutes.
Set TEST mode to TIMED.
Enable On-Error and End-of-Test reports.
Example Procedure Illustrating Menus and Functions:
1.
Press F1 to enter the Analyzer Menu system. At this point you will see
the first page of the Analyzer top level Menu:
F1 F2 F3 F4
MORE TEST WINDOW WORD
2. Press F2 to enter the TEST Menu. You will now see the second page of the
main Menu:
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F1 F2 F3 F4
MORE LENGTH MODE REPORT
3. Press F2 and you will see the LENGTH function:
F1:ESC F2<- ->F3 F4:SET
TEST LENGTH = 01:00:00
NOTE: Your display may show a different value.
4. The TEST LENGTH function allows you to set the length of timed tests in
terms of hours, minutes, and seconds. Notice that either the hours, minutes,
or seconds field will be flashing. To change the value of the flashing field,
press the pattern up/down keys. To change the value of another field, use the
F2 or F3 key to select this field and then use the pattern up/down keys to
change its value.
In this example, we will change TEST LENGTH from 1 hour (as shown
above) to 30 minutes, as shown below:
F1:ESC F2<- ->F3 F4:SET
TEST LENGTH = 00:30:00
5. Note that there are two ways to exit a function like TEST LENGTH. The
normal way is to press F4 to lock in your changes and exit the function.
However you can also exit most functions without making any setup change
by pressing F1 to "escape". In this example we'll press F4 and see the
following:
F1 F2 F3 F4
MORE LENGTH MODE REPORT
6. Notice that we've returned to the TEST Menu. Next press F3 to enter the
MODE function and see the following:
F1:ESC
F4:SET
TEST MODE = UNTIMED
7. Note that the MODE function has only one field and therefore does not use
the F2 and F3 direction keys. Press the pattern up key one time to select the
timed test mode and see the following:
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F1:ESC
F4:SET
TEST MODE = TIMED
8. As before, to lock in this setup change and return to the TEST Menu, press
the F4 key and see:
F1 F2 F3 F4
MORE LENGTH MODE REPORT
9. The last function we'll perform in this example is to enable End-of-Test and
On-Error reports. To do this select the REPORT function by pressing F4 and
see:
F1:ESC
F4:SET
REPORTS ON = NONE
10. Now press the pattern up key three times to select EOT/ERROR which will
enable both End-of-Test and On-Error reports. The REPORT function should
now look like the following:
F1:ESC
F4:SET
REPORTS ON = EOT/ERROR
11. To lock in this change and return to the TEST Menu, press F4:
F1 F2 F3 F4
MORE LENGTH MODE REPORT
12. Since all of the setup goals have been accomplished, we now want to exit the
Analyzer Menu system. To do this from the TEST Menu, or from any Menu,
simply keep pressing the F1 key until the normal display appears. In this
example you would see the following:
a. Press F1 and see the second page of the TEST Menu .
b. Press F1 a second time and see the third page of the TEST Menu.
c. Press F1 a third time and see the first page of the main Menu again.
d. Press F1 a fourth time to see the second page of the main Menu.
e. Press F1 a fifth time and see the third page of the main Menu.
f. Press F1 a sixth time to exit the Menu system and see the normal Analyzer
display format.
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At this point you could perform a 30 minute timed test by:
1. Selecting the TEST display mode (press DISPLAY SELECT until a "T"
appears in front of the BER field) and
2. Pressing the ERROR DETECTION CLEAR key to start a timed test interval.
General Rules for Using the Menu System
Operation of the GB1400 Analyzer and Generator Menu systems can be summed
up by the following rules:
1. From the normal display mode, press F1 to enter the Menu system.
2. Navigate to a particular Menu function by pressing the appropriate "F" keys
to select lower level Menus and finally the desired function.
3. In multi-field functions, use the F2 (move left) or F3 (move right) keys to
select a field. Note that the selected field is indicated by its flashing mode:
flashing = selected, not flashing = not selected.
4. Once a field is selected, use the pattern up/down keys to increment or
decrement the value of the selected field.
5. To exit any setup function, press F4 to lock in all setup changes or F1 to
"escape" without making any setup changes.
6. From any Menu, you can always exit the Menu system by pressing F1 key
one or more times until the normal display format appears.
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Menu Summaries
The GB1400 Generator and Analyzer Menu system may be thought of as a top
level or "main" Menu plus a series of sub-Menus, with each sub-Menu containing
a group of related functions. In this section you will find:
1. A brief description of each Menu found in the GB1400 Menu system.
2. An overall view of the Analyzer Menu system.
3. An overall view of the Generator Menu system.
Note that all Menu names in the following tables below are shown in bold type,
and that all functions included only in instruments equipped with the 1-Mbit
Option are marked with an asterisk (*). Once you have reviewed the summary
tables in this section, please refer to the next section (Menu Functions) for a
detailed description of each GB1400 Menu function.
Table 3-10. Menu Descriptions
Menu
"Main"
Found In Which
Instrument
Analyzer and Generator
Description
Provides access to all other Menus. Also contains a few
functions not part of any other Menu.
TEST
Analyzer only
Contains functions to set up the TEST measurement
process including timing mode, End-of-Test reports, and
the test threshold.
WINDOW
Analyzer only
Contains functions to set up the WINDOW measurement
process including window length and End-of-Window
reports.
WORD
RS-232
PRINT
Analyzer and Generator
Analyzer and Generator
Analyzer only
Contains functions to create and edit WORD patterns.
Contains functions to set up the RS-232C (serial) port.
Contains functions to select which port is used to print
reports and to enable or disable all report printing.
UTIL
Analyzer and Generator
Contains functions to show which options are installed,
and the current software version.
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Table 3-11. Analyzer Menu System Overview
Menu
Page
F1
F2
F3
F4
"Main"
1
2
3
MORE
MORE
EXIT
TEST
RS232
PRINT
WINDOW
GPIB
TIME
WORD
AUTO
UTIL
(to Normal mode)
TEST
1
2
3
MORE
MORE
ESC
LENGTH
THRES
VIEW-CUR
MODE
SQUEL
--
REPORT
PRINT
VIEW-PRE
(to MAIN Menu)
WINDOW
WORD
1
2
MORE
ESC
(to MAIN Menu)
MORE*
ESC
(to MAIN Menu)
MODE
REPORT
BITS
--
SECOND
--
1
2
EDIT*
SYNC*
LENGTH*
FILL*
BUFFER
3
ORDER
RS232
1
2
MORE
ESC
BAUD
EOL
PARITY
XON/XOFF
SIZE
ECHO
(to MAIN Menu)
PRINT
UTIL
1
1
ESC
(to MAIN Menu)
ESC
PORT
ON/OFF
VER
--
--
OPTION
(to MAIN Menu)
NOTES
1.
2.
Menu names appear in bold typeface.
Functions included only in instruments equipped with the 1-Mbit Option
are marked with an asterisk (*).
3.
The ORDER function appears under the F2 key in units not equipped
with the 1-Mbit Option.
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Table 3-12. Generator Menu System Overview
Menu
Page
F1
F2
F3
F4
MAIN
1
2
MORE
EXIT
RS232
UTIL
GPIB
WORD
(to Normal
mode)
RS232
WORD
UTIL
1
2
MORE
ESC
(to MAIN
Menu)
MORE*
ESC
(to MAIN
Menu)
BAUD
EOL
PARITY
XON/XOFF
SIZE
ECHO
1
2
EDIT*
LENGTH*
BUFFER
FILL*
--
3
ORDER
1
ESC
(to MAIN
Menu)
OPTION
VER
--
NOTES:
1.
2.
Menu names appear in bold typeface.
Functions included only in instruments equipped with the 1-Mbit Option
are marked with an asterisk (*).
3.
The ORDER function appears under the F2 key in units not equipped
with the 1-Mbit Option.
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Menu Function Definitions
This section describes each Menu function included in the GB1400 Menu
system. For each function you will find the following information:
·
·
·
·
·
·
·
·
Basic display format
Menu in which it is located
Function name used in the Menu system
Whether it is found in the Analyzer, Generator, or both
Which option(s) must be installed for this function to be available
What this function is used for
Parameters set using this function and their ranges
Notes
Note that most of the following function descriptions are identified by a Menu
name and a function name, for example Test Length. This is to clarify the
application of the described function, and to differentiate functions that have the
same name, for example Word Mode and Window Mode. Also note that function
descriptions are grouped by Menu.
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Word Edit (EDIT)
Format:
F1:ESC F2<- ->F3 F4:SET
WORD AT ddddd = bbbbbbbb
Menu:
WORD
Function Name:
Instruments:
Options:
EDIT
Analyzer and Generator
Requires the 1-Mbit Option.
Application:
Use this function to create new WORD patterns or edit the current
WORD pattern.
Parameters:
Byte Location (ddddd): Set this parameter to the location (in decimal)
of the byte you want to edit in the current WORD. May be set in the
range: 00001 to M+1, where M the number of whole bytes in the
current WORD. If WORD length is M bytes plus N bits, then the
"byte" location of the last N bits is M+1.
Byte Value (bbbbbbbb): This is the binary representation of the
selected byte. Edit this byte using the front panel "bit" keys, MSB 1
... LSB 8.
Range: 00000000 to 11111111 (binary)
Notes:
Use the WORD LENGTH function to set WORD length.
See an additional list of remote commands in the Appendix that
support the 1-Mbit Programmable Word option.
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Word Length (LENGTH)
Format:
F1:ESC F2<- ->F3 F4:SET
LEN:mmmmm BYTES + n BITS
Menu:
WORD
Function Name:
Instruments:
Options:
LENGTH
Analyzer and Generator
Requires the 1-Mbit Option.
Application:
Parameters:
Use this function to set the length of the current WORD pattern.
Bytes (mmmmm): Set this parameter to the number of whole
bytes in the pattern length. That is, if length is M bytes + N bits,
set this parameter to M.
Range: 0 to 16,384
Bits(n): Set this parameter to the number of extra bits in the
pattern length. That is, if length is M bytes + N bits, set this
parameter to N.
Range: 0 to 7.
Notes:
See an additional list of remote commands in the Appendix that
support the 1-Mbit Programmable Word option.
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Word Fill (FILL)
Format:
F1:ESC F4:SET
FILL WORD MEMORY WITH:hh
Menu:
WORD
Function Name:
Instruments:
Options:
FILL
Analyzer and Generator
Requires the 1-Mbit Option.
Application:
Use this function to fill all bytes in the current WORD with the
same 8-bit pattern.
Parameters:
Notes:
Fill Byte (hh): Enter the hex value for the fill byte Range: 00 to
FF.
You may use the fill function as the basis for a new WORD
pattern, then edit individual bytes using the WORD EDIT
function to create the exact pattern that you need.
See an additional list of remote commands in the Appendix that
support the 1-Mbit Programmable Word option.
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Word Order (ORDER)
Format:
F1:ESC F4:SET
WORD ORDER = ccc FIRST
Menu:
WORD
Function
Name:
ORDER
Instruments
Options:
Analyzer and Generator
Requires the 1-Mbit Option.
Application
Use this function to change the transmit or analysis bit order
(MSB first or LSB first) of the current WORD pattern.
Parameters:
Note:
Word Order (ccc): May be set to LSB or MSB.
Word order also applies to the fractional end-byte in patterns that
do not contain an exact multiple of eight bits.
See an additional list of remote commands in the Appendix that
support the 1-Mbit Programmable Word option.
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Word Synchronization Threshold (SYNC)
Format:
F1:ESC F4:SET
WORD SYNC THRES LEVEL= d
Menu:
WORD
Function Name:
Instruments:
Options:
SYNC
Analyzer only
Requires the 1-Mbit Option.
Application:
This function is used to set the BER synchronization threshold used
by the Analyzer for long WORD patterns. This function does not
affect the sync. thresholds for PRBS or short WORD patterns,
which are fixed.
Parameters:
Notes:
Long Word Synchronization Threshold Level (d): Set this
parameter to a level from 1 to 9.
The long WORD synchronization threshold is always set to 256
errors in a rolling window of variable length. The length of this
window is automatically set by the Analyzer, based on the selected
threshold level, so that the nine threshold levels effectively
correspond to the following bit error rates:
Level
BER
1
2
3
4
5
6
7
8
9
3.1 E-02
7.8 E-03
1.9 E-04
9.7E-04
4.8 E-04
2.4 E-04
1.2 E-04
6.1 E-05
3.0 E-05
See an additional list of remote commands in the Appendix that
support the 1-Mbit Programmable Word option.
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Buffer
Format:
F1: ESC
F4: SET
WORD MEM: 0 1M BUFFERS
Menu:
WORD àMORE à BUFFER
Function Name:
BUFFER
Instruments:
Options:
Generator and Analyzer
0 segments 1 Mbit
1 segment
512 kbits
3 segments 256 kbits
6 segments 128 kbits
10 segments 64kbits
Selecting memory locations
Application:
Parameters:
Ten possible WORD memory selections are WORD 0 thorugh
WORD 9.
Notes:
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AUTO
Format:
F1: ESC
F4: SET
AUTO SEARCH MODE
Menu:
Main Menu àF4 à AUTO
Function Name:
AUTO
Instruments:
Options:
Analyzer only
FAST - So-called because of the speed which it determines the
threshold voltage setting, delay, data pattern and polarity.
BER - This method requires the user to set criteria pertaining
to Bit Error Rate threshold and sample size that is used to
determine the size and center of the data eye.
Application:
Parameters:
Automatic setup and synchronization
FAST
BER
Notes:
See the Auto Search Synchronization Application Note at the
end of Chapter 2.
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Test Length (LENGTH)
Format:
F1:ESC F2<- ->F3 F4:SET
TEST LENGTH = hh:mm:ss
Menu:
TEST
Function Name:
Instruments:
Options:
LENGTH
Analyzer only
None required. This is a standard feature.
Application:
Use this function to set the duration of timed tests and the
repeat interval of repeat timed tests.
Parameters:
Notes:
Hours (hh): Set from 00 to 23.
Minutes (mm): Set from 00 to 59.
Seconds (ss): Set from 00 to 59.
Test length does not affect untimed TEST intervals, or the
TOTALIZE or WINDOW measurement processes.
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Test Mode (MODE)
Format:
F1:ESC F4:SET
TEST MODE = ccccccc
Menu:
TEST
Function Name:
Instruments:
Options:
MODE
Analyzer only
None required. This is a standard feature.
Use this function to select a test timing mode.
Application:
Parameters:
Test Timing Mode (ccccccc): May be set to TIMED,
REPEAT, or UNTIMED
Notes:
This function applies only to the TEST measurement process
and has no impact on either the TOTALIZE or WINDOW
measurement processes.
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Test Reports (REPORT)
Format:
F1:ESC F4:SET
REPORTS ON = ccccccccc
Menu:
TEST
Function Name:
Instruments:
Options:
REPORT
Analyzer only
None required. This is a standard feature.
Application:
Use this function to enable or disable End-of-Test and On-
Error reports.
Parameters:
Notes:
Reports On (ccccccccc): May be set to:
NONE: All test reports are disabled.
END OF TEST: Only EOT reports enabled.
ON ERROR: Only On Error reports enabled.
EOT/ERROR: Both EOT and On Error reports enabled.
If you want to generate reports, be sure the ON/OFF function
in the PRINT Menu is set to ON.
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Test Threshold (THRES)
Format:
F1:ESC F4:SET
ERROR THRESHOLD = eeeee
Menu:
TEST
Function Name:
Instruments:
Options:
THRES
Analyzer only
None required. This is a standard feature.
Use this function to set the value of the test threshold.
Test Threshold (eeeee): Set from 1E-03 to 1E-16.
Application:
Parameters:
Notes:
The test threshold affects On-Error reports and the TES
(threshold errored second) result.
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Test Squelch (SQUEL)
Format:
F1:ESC F4:SET
ON ERROR SQUELCH = ccc
Menu:
TEST
Function Name:
Instruments:
Options:
SQUEL
Analyzer only
None required. This is a standard feature.
Application:
Use this function to enable or disable squelching of On-Error
reports.
Parameters:
Notes:
On Error Squelch (ccc): Set to ON or OFF
When On Error Squelch is ON, the analyzer will squelch
(temporarily stop printing) On Error reports after ten
consecutive reports, that is ten consecutive seconds in which
BER exceeds the current test threshold. On Error reports will
resume after 10 consecutive seconds in which the BER does
not exceed the test threshold.
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Test Print (PRINT)
Format:
F1:ESC F4:SET
F4 TO PRINT TEST RESULTS
Menu:
TEST
Function Name:
Instruments:
Options:
PRINT
Analyzer only
None required. This is a standard feature.
Application:
Use this function to print a test summary report based on
current test results (if a test is in progress) or previous test
results (if a test is not in progress).
Parameters:
Notes:
None. This is an immediate function. Simply press F4 to
generate a report or F1 to escape the function without
generating a report.
Make sure the ON/OFF function in the PRINT Menu is ON if
you want to generate a test summary report.
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Test View Previous (VIEW-PRE)
Format:
F1:ESC F4:SET
(result name)(count) (%)
Menu:
TEST
Function Name:
Instruments:
Options:
VIEW-PRE
Analyzer only
None required. This is a standard feature.
Use this function to view results from the last completed test.
Application:
Parameters:
This is an immediate function. After selecting VIEW-PRE
use the pattern up/down keys to scroll through the results
shown below.
START (test start time), STOP (test stop time), ELAPSED
(duration of test), TTL BIT (total number of bits in interval),
TTL ERR (total number of bit errors counted), AVE ERROR
RATE (BER of TEST interval), CUR ERROR RATE (BER
of WINDOW interval), US (Unavailable Seconds), SES
(Severely Errored Seconds), TES (Threshold Errored
Seconds), ES (Errored Seconds), EFS (Error Free Seconds),
DM (Degraded Minutes), SIG LOSS SEC (seconds in which
a loss of signal has occurred), SYNC LOSS SEC (seconds in
which a loss of pattern synchronization has occurred),
PHASE ERR SEC (seconds in which a phase error has
occurred).
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Test View Current (VIEW-CUR)
Format:
F1:ESC F4:SET
(result name)(count) (%)
Menu:
TEST
Function Name:
Instruments:
Options:
VIEW-CUR
Analyzer only
None required. This is a standard feature.
Application:
Use this function to view current test results. In effect this
function takes a snap shot of the latest results from a test in
progress.
Parameters:
Notes:
None. This is an immediate function. Use pattern up/down
keys to scroll through results. Available results are the same
as for VIEW-PRE except that STOP time is replaced by the
message TEST IN PROGRESS
If the TEST process is currently stopped, this function will
display the error message: NO TEST IN PROGRESS.
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Window Mode (MODE)
Format:
F1:ESC F4:SET
WINDOW MODE = ccccccc
Menu:
WINDOW
Function Name:
Instruments:
Options:
MODE
Analyzer only
None required. This is a standard feature.
Application:
Use this function to set window length equal to the number of
bits specified by the WINDOW BITS function, or the time
specified by the WINDOW SECOND function.
Parameters:
Window Mode (ccccccc): May be set to BITS or SECONDS.
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Window Interval in Bits (BITS)
Format: F1:ESC F4:SET
WINDOW LEN = 1.0eEE BITS
Menu:
WINDOW
Function Name:
Instruments:
Options:
BITS
Analyzer only
None required. This is a standard feature.
Application:
When WINDOW MODE is set to BITS, use this function to set
window duration in terms of bits.
Parameters:
Window Length (EE): May be set from 1.0e08 to 1.0e16
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Window Interval in Hrs:Min:Sec (SECOND)
Format:
F1:ESC F2<- ->F3 F4:SET
WINDOW LEN = hh:mm:ss
Menu:
WINDOW
Function Name:
Instruments:
Options:
SECOND
Analyzer only
None required. This is a standard feature.
Application:
When WINDOW MODE is set to SECONDS, use this
function to set window duration in terms of hours, minutes,
and seconds.
Parameters:
Window Length (hh:mm:ss):
hh: Set from 00 to 23
mm: Set from 00 to 59
ss: Set from 00 to 59
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Window Reports (REPORT)
Format:
F1:ESC F4:SET
END OF WINDOW PRINT = ccc
Menu:
WINDOW
Function Name:
Instruments:
Options:
REPORT
Analyzer only
None required. This is a standard feature.
Use this function to enable or disable End-of-Window reports.
End-of-Window Print (ccc): May be set to ON or OFF.
Application:
Parameters:
Notes:
To print End-of-Window reports, be sure ON/OFF parameter in
PRINT Menu is set to ON.
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RS-232 Baud Rate (BAUD)
Format:
F1:ESC F4:SET
BAUD = dddd
Menu:
RS232
Function Name:
Instruments:
Options:
BAUD
Analyzer and Generator
None required. This is a standard feature.
Application:
Use this function to set the baud rate of the serial (RS-232C)
port.
Parameters:
Baud rate (dddd): May be set to 300, 600, 1200, 2400, 4800,
or 9600.
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RS-232 Parity (PARITY)
Format:
F1:ESC F4:SET
PARITY = cccc
Menu:
RS-232
Function Name:
Instruments:
Options:
PARITY
Analyzer and Generator
None required. This is a standard feature.
Use this function to set parity for the serial port.
Parity (cccc): May be set to ODD, EVEN, or NONE
Application:
Parameters:
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RS-232 Data Bits (SIZE)
Format:
F1:ESC F4:SET
SIZE = d
Menu:
RS232
Function Name:
Instruments:
Options:
SIZE
Analyzer and Generator
None required. This is a standard feature.
Application:
Use this function to set the number of data bits per character
for the RS-232 (serial) port.
Parameters:
Number of Data Bits (d): May be set to 7 or 8.
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RS-232 End-of-Line Char. (EOL)
Format:
F1:ESC F4:SET
EOL = ccccc
Menu:
RS232
Function Name:
Instruments:
Options:
EOL
Analyzer and Generator
None required. This is a standard feature.
Application:
Use this function to select an end-of-line terminator. This
character or pair of characters will be added to the end of
every line in reports sent to the RS-232 port.
Parameters:
End-of-Line Terminator (ccccc): May be set to CR/LF,
LF/CR, CR, or LF.
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RS-232 Xon/Xoff (XON/XOFF)
Format:
F1:ESC F4:SET
XON/XOFF ENABLE = ccc
Menu:
RS-232
Function Name:
Instruments:
Options:
XON/XOFF
Analyzer and Generator
None required. This is a standard feature.
Use this function to enable or disable Xon/Xoff flow control.
Application:
Parameters:
Xon/Xoff Flow Control (ccc): May be set to ON (enabled) or
OFF (disabled).
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RS-232 Echo (ECHO)
Format:
F1:ESC F4:SET
RS232 ECHO ENABLE = ccc
Menu:
RS232
Function Name:
Instruments:
Options:
ECHO
Analyzer and Generator
None required. This is a standard feature.
Application:
Use this function to enable or disable character echo on the
RS-232 port. When enabled, the instrument will "echo" (that
is, transmit back to the controller) each character that it
receives on the RS-232 port.
Parameters:
RS-232 Echo Enable (ccc): May be set to ON or OFF.
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Reference
GPIB
Format:
F1:ESC F4:SET
TERMINATOR = cccccc
Menu:
Selected from "main" Menu.
Function Name:
GPIB
Instruments:
Options:
Analyzer and Generator
None required. This is a standard feature.
Application:
Use to select the GPIB end-of-line termination character or
characters.
Parameters:
GPIB End-of-Line Terminator (cccccc): May be set to EOI or
EOI/LF.
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Reference
Utility Option (OPTION)
Format:
F1:ESC
(options listed here)
Menu:
UTIL
Function Name:
Instruments:
Options:
OPTION
Analyzer and Generator
None required. This is a standard feature.
Application:
Use this function to see which options are installed in your
Analyzer or Generator.
Parameters:
None. This is an immediate function.
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Reference
Utility Version (VER)
Format:
F1:ESC
(software version listed here)
Menu:
UTIL
Function Name:
Instruments:
Options:
VER
Analyzer and Generator
None required. This is a standard feature.
Application:
Use this function to see the software version
installed in your unit.
Parameters:
None. This is an immediate function.
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Reference
Time Option (DATE)
Format:
F1:ESC F2<- ->F3 F4:SET
DATE = mmm dd yy
Menu:
Selected from main Menu.
Function Name:
Instruments:
Options:
DATE
Analyzer only
None required. This is a standard feature.
Use to set the Analyzer's internal date function.
Application:
Parameters:
Month (mmm): Set in range JAN, FEB, ..., DEC
Day (dd): Set in range 01, 02, ..., 31
Year (yy): Set in range 93, ..., 99
Notes:
End-of-Test reports are date and time stamped.
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Reference
Time Option (TIME)
Format:
F1:ESC F2<- ->F3 F4:SET
TIME = hh:mm:ss
Menu:
Selected from main Menu.
Function Name:
Instruments:
Options:
TIME
Analyzer only
None required. This is a standard feature.
Use this function to set the instrument's 24-hour internal clock.
Application:
Parameters:
Hours (hh): Set in range 00 - 23
Minutes (mm): Set in range 00 - 59
Seconds (ss): Set in range 00 - 59
Notes:
The Analyzer clock uses a 24-hour format.
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Reference
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Appendices
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Specifications
This appendix details the Specifications of the GB1400 Generator (TX) and GB1400 Analyzer (RX).
Note: The same term can be expressed three different ways.
= CLOCK BAR
= DATA BAR
= NOT CLOCK
= NOT DATA
CLOCK
DATA
GB1400 Generator (TX)
Internal Clock Source
Frequency Range
Step Size Range
Resolution
1 MHz to 1400 MHz
0.01,0.1,1,10,100,1000 MHz
1 kHz
Accuracy
10 ppm (within calibration interval)
Frequency Memory 10 frequencies
External Clock Source
Frequency Range
Burst Mode Option
Input Level
1 MHz to 1400 MHz
150 kHz to 1400 MHz
0.5V to 2.0Vp-p
Impedance
50 Ohm, AC coupled
(with Burst Mode option, 50 Ohm ECL)
SMA
Connector
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Specifications
Data Patterns
Format
NRZ-L, Normal and Complement
PRBS or WORD (User-programmable)
2n-1; n=7,15,17,20,23
Type
PRBS Patterns
WORD Lengths
8 and 16-bit only,
1 Mbit memory (with optional memory)
PRBS Phase Tap Information
The Pseudo-Random data patterns used in the GB1400 TX are generated by shift-register and
exclusive-OR feedback technique. The pattern is dependent on which feedback taps (shift register
outputs) are selected.
For example, PN7 is defined as a seven-stage shift register, which the output of stages 6 and 7 fed
back (through an exclusive-OR gate) to the beginning of the shift register. The feedback taps used
in the GB1400 are tabulated here.
Pattern
PN7
PN15
PN17
PN20
PN23
Feedback
Taps
6
14
14
17
18
7
15
17
20
23
Data Output (True and Complement)
Amplitude
Variable 0.5V to 2.0V, 50 mV steps
Baseline Offset
Variable -2.0V to +1.0V, 50 mV steps
-2.0V to +1.8V, 50 mV steps, with PECL option
Pulse Top Limit
+2.0V into 50 Ohms, +4.0V open load
+2.8V into 50 Ohms (with PECL option)
Rise/Fall Time
Source Impedance
Output Timing
Jitter:
150 pS, typical (20-80%) at 1V amplitude
50 Ohms
CLOCK/DATA edge-aligned (+/- 100 pS)
100 pS, peak-to-peak Max. referenced to EXT clock
SMA
Connectors
Data Inhibit
Rear panel SMA, ECL (50 Ohms to -2V term)
Asynchronous, 1 bit and 500 pS minimum width
Front Panel Selectable
Data Inhibit Rate
Data Invert
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Specifications
Clock Output (True and Complement)
Amplitude
Variable, 0.5V to 2.0V, 50 mV steps
Baseline Offset
Variable, -2.0V to +1.0V, 50 mV steps
-2.0V to +1.8V, 50 mV steps, with PECL option
+2.0V into 50 Ohms, +4V open load
+2.8V into 50 Ohms, with PECL option
150 pS, typical (20-80%) at 1V amplitude
100 pS, peak-to-peak Max. referenced to EXT clock
50 Ohms
Pulse Top Limit
Rise/Fall Time
Jitter:
Source Impedance
Connectors
SMA
Rear Panel Auxiliary Outputs: Phase A, Phase B, Clock/2
Format
NRZ-L
Level
250 mV p-p into 50 Ohms, 50 mV into Hi
1/2 Clock Rate
Clock/ Output
Phase A output
Phase B output
Half rate data pattern
Half rate data pattern
When in WORD mode, Phase A and Phase B outputs are alternating bits.
SMA
Connectors
Error Injection
Internal Rates
External
Single or 1x10n for n=3,4,5,6,7
1 error injected for each rising edge, ECL
Rear panel mounted BNC
Connectors
Front Panel Auxiliary Outputs: Pattern Sync; Clock/4
Level
250 mVp-p into 50 Ohms, 500 mV into Hi-Z
One-bit wide pulse per frame
Quarter Rate Clock
Pattern Sync
Clock/4
Connectors
SMA
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Specifications
RS-232 and GPIB Interfaces
Controlled functions Remote control of all front panel functions except POWER and PANEL LOCK.
Read-back functions
Read-back of ten clock frequencies and ten data patterns stored in non-volatile
memory, unit operating frequency, clock source status, pattern select.
GPIB EOS character LF (line feed) (OA hex)
GPIB Address
Front panel select, 0-30, or OFF-BUS
AC-Power Requirements
Voltage range
Frequency range
Power
90 VAC to 250 VAC, auto-ranging
47-63 Hz
125 VA Max.
Fuse rating
115 VAC; 5 Amp SLO-BLO, 230 VAC 5 Amp SLO-BLO
0 to +50 degrees C
Operating range
Mechanical
Weight
10 Kg (22 lbs.)
Size
152 mm H x 366 mm W x 340 mm D (6" x 14.4" x 13.4")
275 mm (7") (4 RMU)
Rack Height
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Specifications
GB1400 Analyzer
Clock Input
Frequency Range
Input Level
1MHz to 1400 MHz
0.5V to 2.0Vp-p,. Single Ended or Differential
Impedance
50 Ohms, AC coupled (50 Ohm ECL to -2V with BURST MODE option)
Input Threshold
Connector
Non-programmable (fixed threshold levels)
SMA
Burst Mode (option) 150 kHz to 1400 Mhz (ECL Levels)
Data Input
Format
NRZ-L, True or inverted, differential or single-ended
Data Rate
1 to 1400 Mb/s
(Burst Mode option 150 kbps to 1400 Mbps)
-1.5V to +1.0V, 50 mV steps
Input Threshold
Input Level
Impedance
0.5V to 2.0Vp-p, (Single-ended operation requires external cable connection)
50 Ohms
Termination Voltage Selectable, Gnd, -2.0V or AC
Delay Range
Connectors
0-3.99 ns variable, in 5 psS steps
SMA
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Specifications
Data Patterns
Format
NRZ-L
Type
PRBS or WORD (User-programmable)
2n-1 where n =7,15,17,20,23
8- and 16-bit only,
PRSB Patterns
WORD Length
1 Mbit with optional memory
PRBS Phase Tap Information
The Pseudo-Random data patterns used in the GB1400 RX are generated by shift-register and
exclusive-OR feedback technique. The pattern is dependent on which feedback taps (shift register
outputs) are selected.
For example, PN7 is defined as a seven-stage shift register, which the output of stages 6 and 7 fed
back (through an exclusive-OR gate) to the beginning of the shift register. The feedback taps used
in the GB1400 are tabulated here.
Pattern
PN7
PN15
PN17
PN20
PN23
Feedback
Taps
6
14
14
17
18
7
15
17
20
23
Reference Data Input
Format
NRZ-L true
Data Rate
1 Mb/s to 1400 Mb/s
Variable, -1.5 V to +1.0 V, 50 mV steps
0.5V to 1.5Vp-p
Input Threshold
Input Level
Impedance
50 Ohms
Termination Voltage Selectable, Gnd, -2.0V or AC
Delay Range
Connectors
0-3.90 ns, variable, in 100 pS steps
SMA
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Specifications
Auxiliary Signals: Pattern Sync, Clock, Data, Error and Threshold
Level
250 mVp-p into 50 Ohms, 500 mV into Hi-Z
50 Ohms
Impedance
Data Monitor
Clock Monitor
Pattern SYNC
Error Inhibit
Error Output
AUX
Latched Input Data
Buffered Input Clock
1-bit wide pulse per frame
Rear panel, ECL
Rear panel, ECL
Rear panel, Data Threshold output
Note: Connect this output to DATA BAR (Not DATA) for
single-ended operation.
Connectors
SMA
Synchronization
Auto Search
Unit automatically finds the Data Threshold , the Clock/Data input timing phase delay, the input
Data Pattern (PRBS or WORD mode), and Data Polarity.
There are two modes to find the Data Delay
FAST - A quick method using the Clock/Data phase indicator.
BER - A slower method which uses the signal's bit error rate.
Either method will make available the width of the Data Eye (if possible). The BER method
allows user control over:
Data Sample Size (10E-4 to 10E-11). This is the number of data bits sampled at each Delay
setting used to determine the center of the Data Eye.
Bit Error Rate Threshold (10E-3 to 10E-10). This is the threshold used to determine which Delay
settings are part of the Data Eye Crossing.
Manual Mode
User selects parameters, then unit attempts to synchronize on the input data pattern.
Disable Mode
SYNC circuitry disabled
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Specifications
SYNC thresholds
PRBS mode 25% (1024 erros/4096 bits)
WORD mode 3.1% (128 errors/ 4096 bits)
Optional 1 Mbit WORD thresholds, programmable
Level
BER
Ratio (Errors/bits)
256/8192
1
2
3
4
5
6
7
8
9
3.1E-2
7.8E-3
1.9E-3
9.7E-4
4.8E-4
2.4E-4
1.2E-4
6.1E-5
3.0E-5
256/32768
256/131072
256/262144
256/524288
256/1048576
256/2097152
256/4194304
256/8388608
Measurements
BER Measurements
Three simultaneous BER measurements (Totalize, Window and Test) displayed as:
BER
Totalize
9.9E-01 to <1.0E-16
0 to 99999999, then 1.0E8 to 9.9E36
BER since power on or reset
Totalize Mode
Window Mode
BER over sliding window,
programmable in time (1-sec to 24 24-hrs) or bits (1E-8-1E-16)
Test Mode
BER over time of test, programmable in time (1-sec to 24-hrs). Additional
calculations include ES, EFS, TES, SES, DM, US, and LOS.
Frequency
System Clock Frequency, 10 KHz resolution
SYNC loss, Bit Error, Phase Error, Power
History Indicators
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Specifications
RS-232 and GPIB Interfaces
Controlled functions Remote control of all front panel functions except POWER and PANEL LOCK.
Read-back functions
Read-back of ten data patterns stored in non-volatile memory - unit operating
frequency, bit error rate information, sync and history status, pattern select.
GPIB EOS character LF (line feed) (OA hex)
GPIB Address
Front panel select, 0-30, or OFF-BUS
Printer Interface
Format
Parallel Centronics-type and re-directable to serial (RS-232C) or GPIB ports.
Front panel key, prints unit setup
Hardcopy
Print on event
Print on EOW
Print if BER threshold is exceeded; programmable rate (1E-02 to 1E-16)
Print on End of Window,
programmable in time (1 sec - 24 hrs), or bits (1E8-1E16)
Print on EOT
Print on End of Test, programmable rate 1 sec to 24 hours
AC-Power Requirements
Voltage range
Frequency range
Power
90 VAC to 250 VAC, auto-ranging
47-63 Hz
125 VA Max.
Fuse rating
115 VAC; 4 Amp, 230 VAC 2 Amp
0 to +50 degrees C
Operating range
Mechanical
Weight
10 Kg (22 lbs.)
Size
152 mm H x 366 mm W x 340 mm D (6" x 14.4" x 13.4")
275 mm (7") (4 RMU)
Rack Height
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BERT Primer/ Technical Articles
Section Table of Contents
·
BERT Primer, see page B-2
Technical Articles
·
BERT - First and last measurement tool for transmission device design
acceptability, see page B-13
·
·
Ensure Accuracy of Bit Error Rate Tests, see page B-21
Measure Error Rates Quickly and Accurately, see page B-32
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BERT Primer
BERT Definition
A critical element in digital transmission systems is how error-free its
transmissions are. This measurement is made by a bit-error-rate test set (BERTs).
BERTs are not focused or geared to any particular transmission format or
protocol (although they may be capable of emulating a number of such formats);
and are not confined to any specific data rates within their operating range. They
are, therefore, able to function at the most basic “physical layer” of data
transmission, to determine margin for “error-free” transmission, and find the
limits of signal amplitude and transmission rate where a digital transmission
system or device will degrade to unacceptable levels.
BERT used to test “physical layer”
To function at the “physical layer” BERTs must be capable of generating their
own test patterns, and of reporting bit errors versus expected data. The fact that
BERTs can operate at the most basic level of digital data transmission enables
them to be very general purpose, cutting across communications industry
segments. They are employed in the engineering development and test of every
type of data communications device, from semi-conductors and components, to
testing end-to-end transmission paths, such as satellite links or undersea cables.
BERT Building Blocks
BERTs are made-up of a few fundamental building blocks. They are:
·
BERT Generator or Transmitter (Tx)
* Pattern Generator or Memory
* Clock (may be internal or external)
* Data Output Amplifier(s)
·
BERT Analyzer or Receiver (Rx)
* Reference Pattern Generator or Memory
* Data Input Amplifier(s)
* Error Comparator and BER Computation
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BERT Primer
BERT Pattern Generation
Almost all BERT generators include some type of pseudo-random patterns
generation. These “PRBS” patterns are used to stimulate a “Device Under Test”
(DUT) for the purpose of comparing actual received data with the “reference”
data available to the receiver. These PRBS patterns are described below.
PRBS Patterns
A type of data pattern used by most BERTs is called “PRBS” - pseudo-random
binary sequence. PRBS patterns are categorized by the bit-length of the binary
word generating the pattern. For example, a seven-bit PRBS will be output as a
th
serial stream consisting of 27 -1 (2 to the 7 power minus 1 which equals 127
bits). These 127 bits include all possible permutations of seven bits with the
exception of “0000000”. Due to the nature of the Shift Register used to generate
these codes, the code 0000000 never appears. Hence the PRBS pattern is always
of the form “2n - 1”, e.g., 215 - 1, 223- 1.
ITU Specifications (CCITT O.150 and O.151) identify several types of PRBS
patterns used for communications testing. These patterns are usually generated
by hardware shift registers with appropriate feedback. If the shift register has n-
stages, the maximum pattern length will be 2^n - 1.
If the digital signal is taken directly from the output of the shift register (non-
inverted signal), the longest string of consecutive ZERO's will equal n-1. If the
signal is inverted, n consecutive ZERO's will be produced.
Table 1 of ITU Specification O.150 lists several different types of PRBS test
patterns. Some of the recommended test patterns use "non-inverted" signals
(PRBS 9, 11, 23), some use "inverted" signals (PRBS 15), and some use both the
"non-inverted" and the "inverted" signals (PRBS 20).
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BERT Primer
The Tektronix PB200 provides capabilities to invert data on both transmit and
receive. This provides full flexibility to adjust the PRBS signal to the user's
exact requirements. Table B-1 identifies the PB200 polynomial and shift register
feedback taps used to generate PRBS data.
Table B-1 - PRBS Polynomials and shift register feedback taps for PB200
N
Menu Label PRBS
Pattern
Primitive
Polynomial
Feedback Taps
Length in bits
(2N-1 bits)
7
7
PN 7
27-1
x + x + 1
6 and 7
127
511
9
4
9
PN 9
29-1
x + x + 1
5 and 9
10
3
10
11
15
23
31
PN 10
PN 11
PN 15
PN 23
PN 31
210-1
211-1
215-1
223-1
231-1
x + x + 1
7 and 10
9 and 11
14 and 15
18 and 23
28 and 31
1023
11
2
x + x + 1
2047
15
x + x + 1
32,767
23
5
x + x + 1
8,388,607
2,147,483,647
31
3
x + x + 1
The Tektronix GB700/1400 provides capabilities to invert data on both transmit
and receive. This provides full flexibility to adjust the PRBS signal to the user's
exact requirements. Table B-2 identifies the GB700/1400 polynomial and shift
register feedback taps used to generate PRBS data.
Table B-2 - PRBS Polynomials and shift register feedback taps for
GB700/GB1400
N
Menu Label PRBS
Pattern
Primitive
Polynomial
Feedback Taps
Length in bits
(2N-1 bits)
7
7
PN 7
27-1
x + x + 1
6 and 7
127
32,767
15
15
17
20
23
PN 15
PN 17
PN 20
PN 23
215-1
217-1
220-1
223-1
x + x + 1
14 and 15
14 and 17
17 and 20
18 and 23
17
3
x + x + 1
131,071
X20 + x + 1
1,048,575
8,388,607
3
23
5
x + x + 1
B-4
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BERT Primer
PRBS Generation Circuits - A few sample diagrams
PRBS generators are named after the number of combinations they generate; thus
the 28-1 PRBS is generated from 255 unique 8-bit combinations, each producing
one bit in the output stream. The all-zero state is excluded (accounting for the -1),
because it would generate itself and no other combination. Additionally, the
occasional 1 is required to keep a line alive, so an all-zero pattern beyond a
specific bit length should never occur in real traffic. Sample PRBS generators
are shown below:
XOR
Output
D Q1
D Q2
D Q3
CLK
Figure B-1. Three-stage PRBS generator (23-1 PRBS)
Note: Make sure shift registers are not initialized to logical 0’s - this is an
illegal state.
XOR
A
B
D
output
Q1
Q2
Q3
Q4
D
D
D
D
C
CLK
Figure B-2. Four-stage PRBS generator (24-1 PRBS)
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BERT Primer
output
Q1
Q2
Q3
Q4
Q5
Q6
Q7
D
D
D
D
D
D
D
CLK
Figure B-3. Seven-stage PRBS generator (27-1 PRBS) with taps at 6 and 7
The serial patterns generated by the four stage 24-1 PRBS generator (figure B-4
on previous page) is listed below.
Table B-3. 24-1 PRBS pattern for Four Stage PRBS Generator
Clock
1
A
B
C
D
C
XOR D
1
0
0
1
1
0
1
0
1
1
1
1
0
0
0
0
1
0
0
1
1
0
1
0
1
1
1
1
0
0
0
0
1
0
0
1
1
0
1
0
1
1
1
1
0
0
0
0
1
0
0
1
1
0
1
0
1
1
1
1
0
0
1
1
0
1
0
1
1
1
1
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Other Tx Patterns
Other types of digital patterns may be sent by the generator. Some of these are:
·
·
Mark/Space Density (groups of 1’s and 0s)
Custom Pattern entered into the BERT Tx Memory
In some cases, pattern data for error measurement is fed directly to the BERT
Receiver for comparison “in real time” with the received data from the DUT.
The Tektronix GB700 and GB1400 instruments have this capability.
B-6
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BERT Primer
BERT Clock
A clock source is necessary to provide the timing for generation of the BERT
digital output, and to provide the logic strobe for acquisition of the data by the
receiver. The Clock must provide clean, sharp logic transitions and needs to be
delayable to account for time the signals from the BERT take to propagate
through the DUT. Most BERTs have an internal clock source. All BERTs have
the ability to operate using an External Clock. Some BERTs have the ability to
derive the internal clock using an External Reference signal at a fixed frequency,
usually 10 MHz, as a basis for increased stability and frequency accuracy.
Providing External Clock allows the possibility of modulating clock frequency
(adding jitter) in order to stress ability of clock recovery circuit in DUT to
withstand conditions of noise and pulse dispersion typically found in data
transmission systems and circuits.
Output Amplifiers
BERT Output Amplifiers are responsible for providing features such as
amplitude offset, peak-to-peak levels, impedances and the degree to which these
may be set and varied for the purpose of accommodating the DUT, or testing
sensitivity levels of the DUT. These amplifiers also determine or limit the
availability of single-ended or differential output. The typical electrical I/O on
our BERTs is a 1-volt signal centered around ground, either Differential or
Single-Ended. Differential outputs provide an inverted “copy” of the output
signal and are used to drive complimentary inputs. If a single-ended signal is
needed, the complimentary output should always be terminated to the appropriate
load to insure best signal quality.
Data Coding, NRZ
Data generated by a BERT is defined according to certain standard voltage
levels, amplitude swings and transitions which the BERT Receiver will
understand as representing a logical “1” or “0”. The most common type of
encoding is “NRZ” (non-return to zero). For NRZ encoding, consecutive 1’s, for
example, cause the output level to hold at the “true” state, rather than changing
between consecutive bits. The level for NRZ only changes when there is a
transition from 1 to 0, or 0 to 1. Other coding schemes are: RZ (return to zero),
CMI, AMI... and many others. Coding schemes may be optimized to make it
easier to recover clock at the far end, or to attempt to keep voltage levels
balanced on twisted pair conductors.
BERT Receiver or "Error Analyzer" Components
For testing using PRBS, the BERT Analyzer relies on its own internal PRBS
generator to provide a standard for comparison with the incoming bit stream from
the device under test. Transmitters and receivers must be set to the same clock
speed and pattern length.
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BERT Primer
Received Data Pattern Reference
If the transmitter is using some other known standard pattern, such as a particular
Mark-Space Density pattern, a copy of that pattern must also be generated by the
receiver. The BER reference data may be a User Defined pattern. The same
pattern used by the transmitter must be loaded into the analyzer's memory.
Finally, an application specific data stream, supplied at the customer site, may be
fed directly to the BERT Receiver as an external Reference Data source. Not all
BERTs have this feature, but our GB700 and GB1400 both do.
Data Input Amplifier(s)
The BERT input amplifier stage must accommodate a range of data signal
amplitudes, DC offsets and input termination impedances. Most BERTs will
handle either single ended or differential signals and provide a 50-Ohm
termination. Some BERTs, including our GB700 and GB1400, offer either 50 or
75 Ohm input impedance. BERTs typically do not have a great deal of input gain
to accommodate small signals, as oscilloscopes or spectrum analyzers do. Most
of our BERTs require 500 mV signal amplitude for minimum data input levels.
Error Comparator
The BERT receiver compares the incoming data stream bit-by-bit with its
internal pattern using an Exclusive OR gate (XOR) and responds to non-
matching inputs by sending a “1” to a built-in error counter. The number of
errors compared with the number of bits received determines the BER, or Bit-
Error Rate. This is usually expressed as a power of 10 using a negative
exponent, since the fraction of errored bits to total bits must be 1 or less.
BER Computation
Ideally, the BER will be smaller than 10-9 (one errored bit in one billion). A rate
of 10-6 is considered marginal. The size of the counter registers used to count
total bits and errored bits determines the range of BER which the BERT can
measure. The limits will be in terms of how large a BER can be measured (i.e.,
how “bad” the error rate is), as well as how small (how “good”).
Other BER Measurements
BER measurements may be expressed in various ways: Simple errored bit rate,
the ratio of errored to total bits, is usually stated in scientific notation using a
negative power of ten exponent. Other BER statistics include: Total Errored Bits
and Total Bits, Errored Seconds (the number of seconds which contained at least
one bit error), Error-Free Seconds, and other definitions. Many of these are
specified and defined in BellCore and ITU Test Procedures, and other standards.
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Confidence Level in BER Measurement
At first glance, one might think that the BER is known after receiving just one bit
error. It would be expressed as 1 over the total number of bits received. But how
do we know what the “true” BER is? After all, the first errored bit could have
been just a freak “glitch”. In reality, from a statistical confidence point of view,
we must measure long enough to get many errors. This could take a very long
time.
Confidence Requires Collecting Many Errors
If the transmission system had a true BER of 10-12, and we were running at 100
Mb/s, the average time between errors would be 10,000 seconds. At 3600
seconds in an hour, the average time between errors would be nearly 3 hours!
We need more than just one “error event” to have any confidence at all in stating
an “error rate”. Also, the more errors we accumulate, the greater our confidence
level that the BER measurement is truly representative of the device under test.
For a Poisson distribution of errors , BER accuracy is 1 over the square root of
the number of errors. An accuracy of 5% requires 400 errors to have been
counted. Conversely, for 95% confidence that an error rate is less than some
limit, the DUT must be error free for three times the reciprocal of that limit. For
example, to assure an error rate less than 10 per hour, the test must run error free
for 0.3 hours.
Additional Reading
Dr. Dan Wolaver has written an excellent article on confidence levels in BER
measurements titled: “Measure Error Rates Quickly and Accurately".
The article appears later in this section on BERT Technology/ Technical Articles.
Stress Testing
Test times can be dramatically reduced in BER measurement by stressing the
device under test to increase errors. This is done by either:
* Adding Attenuation
* Adding Jitter
* Adding Noise
Attenuation degrades S/N (signal-to-noise) ratio, and thus reduces the size of the
data “eye” in amplitude. Adding jitter on the clock (modulating the clock period,
causing the clock edge to jump around) effectively reduces the data “eye” in
width. A third technique is to add noise, which also degrades S/N. Any of
these methods will increase the BER in a known way which allows extrapolation
of what the error rate would be without stress. Measuring BER in the presence of
added stress is an essential technique in testing high quality (very low error rate)
systems quickly.
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Other BERT Features
In addition to measuring Bit Error Rate, BERTs may have additional features
which enhance ease of use or expand test capabilities. Some of these might be:
* Eye Width Measurement
* Auto Synch Feature
* Pattern Locking Methods
* Pattern Loading Software
* Error Insertion
* Internal Jitter Generation
Eye Width Measurement
Since the BERT Receiver must have the ability to delay the received clock, it
may have the ability to run the clock edge through a range sufficient to cover the
received data “eye” . The “eye” width is the time during which the received data
exhibits clean logic “1” or “0” levels. Ideally the “eye width” is one over the bit
rate. At the edge of the “eye”, the signal is transitioning from one level to the
other. The “Eye Width” for any Error Rate is a measure of a system’s timing
and jitter tolerance. A designer might have to meet a spec such as “eye width at
500Mb/s and 10-9 BER must be 1.0ns or greater”. The manufacturer is then
confident that there is sufficient margin in his product to live up to his customers’
expectations. Vertical compression of the eye (from ISI, echoes, regenerator
output variations, decision-level instability, etc.) from ideal can be used to
extrapolate error rate, and derive minimum S/N ratios to assure specified
performance.
The user should run the test equipment back-to-back (i.e., Transmitter connected
directly to Receiver with no device in the test path) first, to establish maximum
eye width. BERTs inherently have their own set-up and hold times, so back-to-
back results will always be a little less than perfect.
Auto-Synch
Auto-Synch is the ability of the BERT Receiver to search in time and in
amplitude level for the optimum place to put the Clock edge for the cleanest logic
level information. This positioning must be done, whether automatically or
manually, before any meaningful BER measurement can be made. All of our
BERT products have this Auto-Synch feature.
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Pattern Lock
Before a BER measurement can be made, the BERT Transmitter and Receiver
must be using the same test pattern. This may be guaranteed if they use the same
PRBS or fixed word pattern and are running at the same clock rate, but there is
still the issue of having the bit comparison begin at the same point in the pattern.
All of our general purpose BERTs have the ability to do an “auto search” for
pattern lock. There are two techniques commonly used for this: the “bit slip” or
“clock slip” method, and the “feed forward” method.
In the “bit slip” method, each error detected causes a one-bit slip in the reference
pattern, until the beginning of the pattern is reached. This is normally the only
method that can be used with custom data structures or word patterns. This is the
method the GB1400 uses to synchronize any data pattern. This is also the
method used for WORD patterns with the GB700 and GB1400 instruments.
With the “bit slip” method, synchronization times will vary by the length of the
pattern. The longer the pattern, the longer the sync time.
In the “feed forward” method, which works for PRBS patterns only, a certain
number of arriving bits are latched into the Receivers PRBS shift register and
used as the “seed” for the start of the PRBS generation. This is the method the
GB700 and GB1400 use for PRBS synchronization.
Both methods rely on realizing some minimum acceptable BER before the
Receiver considers it has obtained “pattern lock”. It will then begin
accumulating “bit errors” in the error counter register.
Pattern Loading Software
Almost all BERTs have the ability to accept loading of reference patterns into
internal memories in both transmitter and receiver. In many cases this is via
computer interface, either RS-232 or GPIB. The GB1400 has an front panel
floppy disk drive to load patterns. The GB700 and GB1400 use either RS-232
or GPIB.
Pattern creation software is a valuable aid in developing custom patterns. A
simple spread-sheet like tool is available for our BERT products to help with this
need.
Error Insertion
Most BERTs have the ability to internally generate bit errors, either singly or at
specific bit error rates. This calls for altering bits in the output pattern which are
opposite from the bits the receiver will use at that location, thus causing the
Receiver to tally a bit error. This feature may be important in measuring ability
of device under test to withstand or recover from such errors. Some BERTs,
including our GB700, will allow an external “trigger” signal to cause an
immediate bit error to be output.
Error insertion is also a useful tool to test the “integrity” of your equipment
setup. You should always insert a few errors in your setup to conform correct
operation before you start your data collection.
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Jitter Generation
Some BERTs have the ability to generate and impose jitter on the internal clock.
A jittered External Clock input is the means for adding jitter to the Tx source on
GB700 and GB1400 BERT instruments.
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Technical note
BERT - first and last measurement tool for
transmission device design acceptability
Bit error rate testers (BERTs) are the basic tool for testing the quality of transmission systems
and circuit elements. The job of the BERT is simple - to feed test patterns bit-by-bit through the
transmission path or device-under-test (DUT), and confirm that the error rate is sufficiently low.
Typical acceptable error rates might be one in one billion bits or lower.
Under the hood, BERTs are all 1s and 0s. The general-purpose BERT, one that would be used in
developing and testing serial transmission designs, independent of any communications
protocols, operates entirely on this level. You have control of the frequency (bits per second),
pattern, output amplitude and timing, and can tweak these values to stress a system to determine
the margin conditions of "acceptable" operation, and reveal design weaknesses.
Some BERTs are also designed to test quality at the data link layer of a data transmission
interface/electrical specification or protocol, beyond simply running at the correct operating
frequencies and tolerances for the standard. These BERTs are able to recognize frames/packets
and generate them, emulating the data formats called for in the standards. They are useful while
protocol standards are being hashed out. When a protocol becomes firm and established, the
BERT is replaced by the Protocol Analyzer.
The Tektronix family of BERT products (listed at the end of this article, along with specific
functionality) all conform to the above description, but differ from each other in frequency range,
number of channels, and pattern and format generation capability.
Bit error rate testing
A BERT's basic measurement is the bit error rate (BER), defined as the number of bit errors over
the total number of bits sent. This is a small, positive number, generally in the range of 10-6 to
10-15. After the user connects the BERT to both ends of the transmission system or subsystem to
be tested, the transmitter half of the BERT sends digital test patterns across the system.
The receiver half at the other end finds the incoming signal and determines the best "decision"
voltage level and compensates for phase delay to place clock edge at the optimum point. Both
BERT Transmitter and Receiver generate the same test pattern internally using the same
algorithm, and the Receiver synchronizes its internal pattern with the pattern coming from the
Transmitter.
Simply knowing the total number of errors, however, will not help much in identifying the error
sources. Other measurements include a time dimension that can help in nailing down a source of
error. Errored seconds (ES) is the number of seconds during there was as least one bit in error.
Severely errored seconds (SES) has a BER of 10-3 or greater. Consecutive SES is the measure of
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SESs for which the previous two seconds were also SESs. Some BERTs will graph these and
other errors over time to illustrate clumping or mark events.
How long is long enough?
Every time the BERT detects an error, it logs another check mark in the error column and
updates the other various measurements it makes. At what point, however, can you say that the
various measurements give an accurate representation of your system? Consider: With a BER of
10-15, a 1 Gb/s system will encounter an error every 11.5 days.
A valid test certainly requires more than a single error to offer statistically relevant results (see
Table 1). Random sampling is just that - random. Your design may have encountered a burst of
errors that won't happen again for another three months (perhaps due to some unusual electrical
interference), but if the sample was not large enough to tell you otherwise, you would consider
the device bad. Also consider the inverse where a bad system appears good.
Table 1. Length of Test for Evaluation of 1 Gb/s System
68% confidence
(10 errors)
90% confidence
(100 errors)
BER
10-9
10-12
10-15
10 seconds
2.8 hours
116 days
1.7 minutes
1.2 days
3.17 years
Testing until you have ten errors offers only a 68% confidence in the BER, while 100 errors
offers 90% confidence. Think about how long it would take to obtain 90% confidence in systems
running at 1 Mb/s or 19.2 kilobaud, if you were looking for a 10-9 BER. So how do you get
around taking 3.17 years to thoroughly test that 1 Gb/s system with a BER of 10-15?
Stressing the transmission system
One answer is to stress the system and increase the error rate. Error rates measured while a
system is under stress can be extrapolated to lower error rates for the system with no stress. First,
take a thorough reading of the design's performance under normal operating conditions. Then, by
collecting BERs for the system under different levels of stress, you can determine a performance
curve.
For example, adding 3 dB of attenuation to impair signal levels, (see Figure 1), the system might
show a BER of 5 x 10-6. This corresponds to a BER of 10-10 for the system without attenuation
stress. The goal is not to determine the actual error rate, but the upper bound on the error rate. By
stressing the system and increasing the error rate experienced, testing can take significantly less
time (more errors in a shorter time), while still offering an accurate representation of the system's
quality.
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1
10
10
10
2
3
BER
4
10
10
10
10
10
10
5
6
7
8
9
10
11
12
13
14
15
16
10
10
10
10
10
10
10
7
8
9
10 11 12 13 14 15 16 17 18
SNR (dB)
Figure 1. Bit-Error-Rate (BER) is plotted here as a function of the signal-to-noise ratio (SNR),
where SNR is S/Nrms in decibels (electrical), S is magnitude of difference between the signal (1 or
0) and the decision threshold and Nrms is the rms value of the Gaussian noise riding on the signal
There are four major sources of error in any digital system: noise, jitter, baseline wander, and
intersymbol interference (ISI). A fair number of errors will come from noise; there will always
be background errors. In general, noise manifests itself as random errors that appear infrequently
and sporadically, unless there is a strong source of noise close by.
However, if a great many errors occur in a short period of time, you may be able to correlate the
burst of errors with other events, either natural (lightning around a microwave radio tower) or
man-made (running your test at precisely the same time as the once-a-month test of the back-up
diesel generator).
Jitter, undesired variations in the timing of edge transitions in clock or data waveforms, can
cause frame or clock slips. A certain amount of jitter (residual or incidental jitter) is inevitable
due to phase noise in oscillators, voltage hysterisis in switching transistors, etc.
We can deliberately add jitter into the system by supplying a jittered clock for the BERT
transmitter. This allows us to see how susceptible to jitter clock recovery circuits are. We can
also see whether a transmission circuit element will add jitter. As with adding attenuation,
stressing the transmission system with a certain level of jitter can be a good predictor of error
performance with no added jitter stress.
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ISI errors are caused when particular patterns (symbols) of data interfere with each other, leading
to blurring and smearing of signals. An example of ISI can be illustrated by following a square
wave (1010....). When the signal leaves the transmitter, the corners of the square wave are
sharply defined. As the signal travels a couple of miles over a transmission medium, attenuation
(a function of distance) sets in. The digital waveform experiences phase delay, dependent upon
the frequency of the signal components. As a consequence, the square corners become more
rounded and blend into each other, making it difficult to tell where a pulse starts and stops. The
tails of data pulses interfere with following data and reduce the eye opening (example shown in
Figure 2).
Superimposed
pulses with jitter
modulation
Ideal pulse
position
- Peak
+ Peak
Jitter modulation
Figure 2. Example of a "Eye Diagram" as viewed on an oscilloscope. Pulse rounding is due to
phase dispersion, causing ISI.
By purposely adding noise, jitter or stress patterns, you can stress your design. An external
attenuator can crank a known dB of loss into the transmission path. BERTs can add jitter by
using a dithered clock so as to impair timing. Baseline wander can be tested by pattern stressing
(what happens after a long string of 0s?), causing dc drift and reducing the amplitude of the
decision threshold.
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Stressing through pattern generation
One common stress test employs a pseudorandom binary sequence (PRBS) generator to create
test data. The PRBS generator is seeded with a nonzero pattern of n bits. Using a shift register
with XOR feedback, the PRBS will cycle endlessly through every combination of n-bits (except
for the all-zero state), with no repeats until every combination has been generated (see Figure 3
and Table 2 for the 24-1 PRBS).
XOR
A
B
C
D
Figure 3. 24-1 PRBS (pseudorandom binary sequence) generator
Table 2. 24-1 PRBS pattern
Clock
1
A
1
0
0
1
1
0
1
0
1
1
1
1
0
0
0
B
0
1
0
0
1
1
0
1
0
1
1
1
1
0
0
C
0
0
1
0
0
1
1
0
1
0
1
1
1
1
0
D
0
0
0
1
0
0
1
1
0
1
0
1
1
1
1
C XOR D
0
0
1
1
0
1
0
1
1
1
1
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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PRBS generators are named after the number of combinations they generate; thus the 28-1 PRBS
is generated from 255 unique 8-bit combinations, each producing one bit in the output stream.
The all-zero state is excluded (accounting for the -1 in 28-1", above), because it would generate
itself and no other combination.
The purpose of a PRBS is to stress a system by testing possible combinations of data that could
pass through the device, bringing out different types of problems. PRBSs have predictable
patterns, consisting of strings of 1s and 0s.
For example, the 8th through the 11th bits of the 24-1 PRBS are all 1s (see Table 2), followed by
three 0s. If we were looking at a 231-1 PRBS, at some point, we would set thirty-one 1s and later
thirty 0s would cycle through the system. Such a sequence of patterns could cause the data
baseline to wander.
Depending on your application, PRBSs may not simulate the kind of traffic you expect to see
across your lines. Again, the goal of the PRBS is to stress your system in ways that help you to
understand its limits and the quality you can expect from it under ordinary circumstances. Note
that the shorter PRBSs are quicker to repeat: a 28-1 PRBS repeats every 255 bits, whereas a 231-1
PRBS repeats every 2,147,483,647 bits.
ITU Specifications (O.150 and O.151) identify several types of PRBS patterns used for
communications testing. These patterns are usually generated by hardware shift registers with
appropriate feedback. If the shift register has n-stages, the maximum pattern length will be
2^n - 1.
If the digital signal is taken directly from the output of the shift register (non-inverted signal), the
longest string of consecutive ZEROs will equal n-1. If the signal is inverted, n consecutive
ZEROs will be produced.
The ITU Specification O.150 lists several different types of PRBS test patterns. Some of the
recommended test patterns use "non-inverted" signals (PRBS 9, 11, 23), some use "inverted"
signals (PRBS 15), and some use both the "non-inverted" and the "inverted" signals (PRBS 20).
Tektronix GB700/ GB1400 BERTs provide the ability to invert data on both transmit and
receive. This provides full flexibility to adjust the PRBS signal to the user's exact requirements.
A cousin of the PRBS is the quasirandom signal source (QRSS). QRSS patterns constrain the
number of 0s that can appear within a sequence (for example, a 220-1 pattern with no more than
fourteen 0s within each 20-bit combination). QRSS patterns can also be named n:x, short for
n-in-x (for example, the 3:24 QRSS cycles through all combinations that contain three 1s and
twenty-one 0s).
Other pattern generating options might include all 1s (1111...), all 0s (000...), or alternating 1s
and 0s (1010...), or mark density. In general, cycling through several different patterns tends to
stress a system more than continuously running a single pattern.
Most BERTs have internal memory to allow the creation and storing of your own test patterns.
These patterns may be real traffic, combinations that stress particular aspects of your design, or
data with intentional errors. Some BERTs allow you to mix saved patterns and generated
patterns.
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For example, you could use a saved pattern to create an ATM header and a generated pattern to
populate the packet with random data, allowing you to build test data that looks more like "live
traffic". If you are testing an error-correcting circuit on a modem, the transmitted pattern could
have parity errors that the modem should correct. Because the receiver can reference different
patterns independent of each other, the "expected" pattern could reflect what the corrected data
should look like with the errors fixed.
= = = = = = = = = = = = = =
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Technical Article from 5/9/91 Electronic Design magazine
Ensure Accuracy Of Bit-Error Rate Tests
By Dan Wolaver and James Hanley, Tektronix
==========
To properly evaluate digital transmission systems, users must understand their BER
tester’s specifications.
==========
A critical element in a digital transmission system is how error-free its transmissions are. This
measurement is made by a bit-error-rate tester (BERT), which replaces one or more of the system’s
components during a test transmission.
A BERT must be able to mimic normal and stress conditions and must not be the first component to fail
when the system is stressed. Moreover, a BERT’s data pattern and clock quality typically differ from
those of the system under test.
Consequently, users must know how to obtain and understand these important specifications to ensure an
accurate picture of their system’s capabilities.
A digital transmission system (see figure below) includes a data source-such as computer memory, a
voice digitizer, or a multiplexer--that originates a digital signal, D.
C
D
F
H
Clock
Source
Data
Source
Driver
System
under test
Line
Receiver
Decision
circuit
Data
G
Clock
Input
Clock
Recovery
C
D
Threshold
F
Sampling instant
G
H
Figure 1. In a typical digital transmission system, the data signal, D is corrupted by noise and
pulse dispersion. As a result, the received signal, F, is distorted.
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A clock source produces a clock signal, C, that times the occurrence of each bit in the digital signal. A
driver, which may be a power amplifier, a laser diode, an RF modulator, or a tape head, prepares the
signal for the system under test. The system under test can be a transmission line with repeaters, or an
optical fiber link, microwave radio link, or digital tape recorder. The received signal, F, exhibits the noise
and pulse dispersion that the transmission system adds to the digital signal.
If the noise and distortion are within limits, the decision circuit can correctly decide whether the original
bit was a 1 or a 0. The circuit does this by comparing F (at sampling instants determined by clock signal
G) with a threshold halfway between the two levels. If no errors are made in the decision process, H is a
delayed replica of the original data signal D. A clock-recovery circuit generates G from information in
data signal F.
A malfunction in any system component can cause the recovered data to differ from the original data. The
primary job of a BERT is to determine the system’s error rate rather than isolate the faulty component.
But for the sake of convenience, the BERT may replace the clock source in the transmitter or receiver.
In this case, some fault isolation may be possible by comparing the performance of the system clock
sources with that of the BERT. But for the comparison to be meaningful, users must understand the
timing jitter specifications of both units.
To measure the system’s error rate, the test set performs one or more of the following pairs of functions:
·
·
·
data-pattern generation and error monitoring;
clock generation and recovery; and,
jitter generation and measurement.
Which functions are used depends on how the BERT is connected in the system.
The simplest measuring technique (see the following figure) is to replace the system’s data source with
the BERT’s data-pattern generator and have the BERT receiver monitor the recovered signal for errors.
The data signal D then becomes D¢. The data-pattern generator can mimic typical traffic by creating
pseudorandom patterns, or it can stress the system by outputting fixed patterns stored in memory.
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BERT
receiver
Data pattern
generator
H’
H
G
F
Clock
Data
Driver
System
Line
Decision
circuit
Error
monitor
Source
Source
under test
receiver
C
D’
Data pattern
generator
Clock
recovery
(a)
BERT
transmitter
Data pattern
generator
BERT
receiver
H’
H
G
F
Decision
circuit
Error
monitor
Line
receiver
Clock
Source
Data
Source
System
under test
Driver
G’
C’
D’
Clock
Source
Data pattern
generator
Clock
recovery
Clock
recovery
(b)
BERT
transmitter
G’
Jitter
Jitter
generator
measurement
Figure 2. In the simplest use of a bit-error-rate tester, the instrument creates a known data signal,
D'. At the receive end, the BERT duplicates that signal so it can compared with the transmitted
version (see flowchart a).
In some cases, the BERT may supply the system clock signal and even add a known jitter that can
be measured at the receive end (see flowchart b). If the BERT supplies the clock, the instrument's
clock source and clock recovery-circuit must be at least as good as their counterparts in the
system under test.
Supplying Data Patterns
To monitor the transmission, the BERT receiver generates its own data pattern, H¢, which is the same as
the desired data, D¢. The BERT receiver compares the received signal, H, with H¢, and looks for errors.
The tester records the total number of errors, the ratio of errors to bits (the bit error rate), the number of
“errored” seconds (ES), and the ratio of ES to total seconds.
To make a valid comparison, the BERT receiver must synchronize H¢ with H. Accomplishing
synchronization depends on whether the data is a fixed or psuedorandom pattern.
Sometimes it is convenient for the BERT to supply its own clock signals for its transmitter and/or its
receiver. For instance, the system clock may be unavailable in a field situation, or the test engineer may
want to avoid the trouble of providing and phasing the clock at the BERT receiver. In this case, the
BERT’s transmitter clock is C¢, and its receiver clock is G¢ (see the figure above for reference). In
laboratory applications, it is common for the BERT to provide a wide range of clock frequencies.
The BERT’s clock source and clock-recovery circuit must be as good as their counterparts in the system
under test. The source must introduce negligible time jitter, because phase jitter in C¢ causes phase jitter in
the recovered clock signal, G, relative to the received data signal, F.
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Likewise, the BERT’s clock-recovery circuit must tolerate at least as much jitter as the system’s recovery
circuit without causing errors.
Although the BERT clock source should be essentially jitter-free to test the digital transmission system
under normal conditions, users may wish to stress the system at times. In that case, the BERT must
generate controlled jitter. To do so, some BERTs have a jitter generator that can sinusoidally modulate the
phase of the clock source.
On the receive end, the BERT monitors the effect of the controlled jitter in two ways: First it looks for an
increased error rate, then it measures the jitter remaining in the recovered data. The second measurement
yields the system’s jitter-transfer function. The jitter-measurement circuit can also be used without the
jitter generator to measure the system’s own jitter.
The BERT transmitter’s principal task is to send a data pattern to the transmission system. The most
general scheme is a repeating pattern that can be as short as 8 bits or as long as thousands of bits. Users
can design the pattern to exercise the system in a number of ways, including noise margin and clock-
recovery stressing.
Noise-Margin Stressing
The quality of signal F determines whether the digital transmission system decides correctly between a
logic 1 and a logic 0. That quality depends on the noise margin, which is the separation between F and the
logic threshold at the sampling point. Any distortion (usually due to a nonflat frequency response in the
linear channel) reduces the noise margin. If the noise margin is large, the error rate is essentially zero and
doesn’t indicate the margin.
A BERT, however, can measure the noise margin by reducing it in a controlled way until the error rate is
significant. The measurement uses what’s called baseline wander. Most transmission systems are AC
coupled to suppress the effects of biasing and DC offsets (see the following figure).
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0.1 m F
D’
C
R
50
(a)
D’
1
Avergage = -0.5
Average = 0.5
Time
-1
Pattern A
Pattern B
Pattern A
1
(b)
F
2
1
-1
Time
RC
0.5
0.5
(c)
Figure 3. (a) Most transmission systems use AC coupling.
(b) Consequently, a bit-error-rate tester can measure the system's noise margin by generating
signal patterns with an unbalanced number of 1s and 0s.
(c) The result is baseline wander, which reduces the margin between the received signal, F, and
the threshold.
As long as the number of 1s and 0s in the data pattern is equal, the pattern’s DC content is fixed, and the
coupling circuit doesn’t block anything important. If the balance changes at a low frequency, the
coupling circuit may block that frequency, causing F to wander up and down. This baseline wander
reduces the noise margin.
Properly designed transmission systems ensure that data patterns have no frequency components below
the coupling circuit’s cutoff, essentially eliminating baseline wander. But a BERT can purposely
introduce some baseline wander to measure the noise margin.
An example is an input signal D’ that starts with a 10001000 pattern and switches to a 11101110 pattern.
During the first imbalanced pattern, the average voltage, -0.5 V is blocked by the coupling circuit, and the
output F has an average of 0 V. When the pattern changes to 11101110, D¢ averages 0.5 . After a transient
with a time constant of RC=5ms, the average of F returns to zero, and the signal has wandered by half of
its amplitude.
This baseline wander reduces the margin between F and the threshold by 50%, to 0.5 V from 1.0 V. If this
reduction caused the error rate to become measurable--say 10-6--the conclusion is that the original margin
was about 50%.
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To stress the noise margin continuously, the tester alternates between 10001000 (pattern A) and
11101110 (pattern B) at a frequency below the AC coupling circuit’s cutoff frequency. Each pattern
continues long enough for the circuit’s transient to die out. A duration of 3.14 time constants, or pRC, is
sufficient. Therefore, the complete fixed pattern stored in memory has a period of at least 2pRC. The
frequency of the pattern is at most 1/2pRC, which is the cutoff frequency, fL, of the coupling circuit.
Then if the bit rate is fc, the number of bits in the fixed pattern is:
N ³ fc / fL
For example, if fl=32kHz and fc=1 Gbit/s, the fixed data pattern must be at least N = 1 Gbit/s/ 32kHz =
31,200 bits long.
Users can create different stress levels by combining the above patterns with patterns that have an equal
number of 1s and 0s, thus causing no stress in a system with AC coupling. For example, the pattern
11001100 won’t change the DC content or noise margin. By combining various amounts of this balanced
pattern with the previous unbalanced patterns, users can stress the system to varying degrees, up to 50%
(see table below).
Table 1. Data patterns for noise margin stressing
Pattern A
Pattern B
Margin reduction
0 %
1100110011001100
1000110011001100
1000110010001100
1100110011001100
1110110011001100
1110110011101100
12.5 %
25.0 %
1000100010001000
1110111011101110
50.0%
Other patterns such as 1000000010000000, stress the noise margin by more than 50%, but they also stress
the clock-recovery circuit, which may be undesirable.
Users who want to stress the clock-recovery circuit can do so by varying the transition density. This is
because the system’s receiver gets its information from the received data signal. For nonreturn-to-zero
data, the clock information is in the data transitions. Random data contains an equal number of 0-to-1 and
1-to-0 transitions, and a clock-recovery circuit is usually designed to expect this 50% transitions density.
The circuit may have trouble with either a greater or lesser density.
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The simplest fixed pattern with a 50% transition density is again 11001100. The patterns in Table 1 that
stress noise margin by varying the balance of 1s and 0s also maintain a 50% transition density. Similarly,
patterns that stress the clock-recovery circuit by varying transition density should keep the 1s and 0s in
balance (see the following table).
Table 2. Data patterns for clock recovery stressing
Pattern
Transition density
1010101010101010
1010110010101100
1100110011001100
11001110001100111000
111000111000111000
11100011100011110000
1111000011110000
100%
75%
50% (normal)
40%
33%
30%
25%
As the transition density is increased or decreased from 50%, the clock-recovery circuit will fail and the
error rate will become significant. A well-designed clock recovery will typically tolerate transition
densities between 100% and 25% without causing errors.
Data Patterns Stored
Fixed patterns can also be designed to simulate valid line formats in telecommunications.
One such format is DS2, the third level in the North American digital hierarchy at 6.312 Mbits/s. The
DS2 frame is 1176 bits long, organized into 24 groups of 49 bits. The first bit in each group of 49 is a
framing bit or a control bit, and the rest are data bits. A BERT transmitter can generate such a pattern to
test terminal equipment that looks for the framing and control bits.
Fixed data patterns are stored in the BERT transmitter. User-defined patterns are stored in RAM, and
manufacturer-provided patterns are stored in ROM.
The BERT receiver must be programmed to produce the same data pattern as the transmitter. The receiver
synchronizes its pattern, H’, to the received data pattern, H, on the basis of error rate. If the error rate is
greater than some set level, say 10-2, H’ is shifted one bit by dropping a clock pulse. This continues until
the synchronization is achieved, as indicated by an error rate less than 10-2.
Another type of pattern, a psuedorandom bit sequence (PRBS), simulates live traffic. A PRBS has all of
the properties of a random sequence but is periodic. A fixed pattern could be programmed to produce a
PRBS, but a simple circuit can generate a pattern millions of bits long with only 20 to 30 bits of memory.
Common pattern lengths are N=27-1, 215-1, and 223-1.
PRBS patterns can stress the noise margin and the clock recovery as fixed patterns do. But it is done
randomly, somewhat like live traffic. When averaged over the whole sequence, the number of 1s and 0s
almost equal (actually different by one), and transition density is 50%. Over a short term, though, the
averages can be very different, stressing both noise margin and clock recovery for periods of time.
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To stress the noise margin, the PRBS spectrum must have components below the coupling circuit’s cutoff
frequency, fL. For example, a 23-stage PRBS generator with a bit rate, fc, of 44.7 Mbits/s has a pattern
length of 223-1=8,388,607 bits.
The fundamental frequency, fF, is fc/8,388,607=5.33 Hz. If fL=32 kHz, thousands of the pattern’s spectral
components are removed. The fraction of power removed is given by pfL/fc, and the square root of that
figure is the rms error as a fraction of the signal level:
rms error =
pfL/fc = 0.047
This error appears as Gaussian noise with an rms value that is 4.7% of the noise margin. The more
spectral components below the cutoff frequency, the more Gaussian the noise is. However, if fundamental
would be the PRBS pattern length was 27-1, the 350 kHz, which is greater than fL. The noise margin
wouldn’t be stressed, and the formula for rms error wouldn’t hold.
Similarly, a PRBS pattern will stress the clock-recovery circuit if the pattern’s fundamental is within the
B. If it is, the pattern introduces random fitter in the recovered clock. The jitter’s
magnitude depends on fB and on offsets within the circuit. The rms jitter is not a function of the PRBS
pattern length, but the peak jitter increases with pattern length.
Examining Jitter
An important factor in a data transmission system is jitter. Ideally, all clock and data signals in the
systems have a constant frequency with no phase modulation. In practice, a clock source has some phase
modulation, or jitter, and noise and imperfect equalization introduce additional jitter. The following
discussion examines clock-source jitter alone, assuming that noise and distortion contribute no jitter.
If the received data waveform, F, is viewed on an oscilloscope synchronized data, the 1s and 0s overlap to
produce an “eye” pattern (see figure below).
Superimposed pulses
with jitter modulation
Ideal pulse
position
- Peak
+ Peak
Jitter modulation
Figure 4. Viewed on an oscilloscope synchronized to the received data, phase error, or jitter, qe
shows up as a widening of the recovered clock's waveform.
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If the transmitter clock source has phase jitter q , the received data signal, F, has the same jitter. But the
i
eye pattern does not display this jitter because the scope is synchronized to the data.
In general, qo, which is the phase of the recovered clock signal, G, cannot track q, exactly, so some phase
i
error (qe=q-qo) exists between the clock and the data. With the oscilloscope synchronized to the data, this
i
error is seen as a broadening of the recovered clock’s trace. The trace’s width is the peak-to-peak value of
the phase error jitter.
Phase error can cause a problem when the clock’s rising edge samples the received data to see if it is
above or below the threshold. If the phase error is too great, the rising clock edge approaches the sides of
the data eye pattern, and the transmission system’s decision circuit makes errors.
If the spectral density of the clock-source phase jitter F qi (f) and the clock recovery bandwidth fB are
known, the rms phase error can be calculated:
qerms
=
(p/2)fBF (fB)
(Equation 1)
qi
BERT manufacturers sometimes specify the clock’s single-sideband noise density, F (f), at an offset
vi
frequency of 10 kHz, which is also the value of F vi (10 kHz). From this figure, the value of Fqi (fB) can
be approximated by:
Fqi (fB)=(10 kHz/fB)2Fqi(10 kHz).
For example, if Fvi(fc+10 kHz) is -84dBc/Hz, then:
Fqi(10 kHz)
=10-84/10
=2.5´ 10-9 rad2/Hz
and for fB=16 kHz,
-9
Fqi(fB)=(10 kHz/16 kHz)2´ (2.5´ 10-9)=10 rad2/Hz.
If the BERT manufacturer supplies no information on clock-source jitter, the user must measure the
spectral density.
Once fB and F (fB) are known, the rms phase error qerms can be calculated from Equation 1.
qi
Typical spectral density at fc=70 Mhz and fB=16 kHz is 10-9 rad2/Hz. For these specifications, Equation 1
yields an rms phase error of 0.005 rad, or about 0.0008 UI (unit intervals), where 1 UI=2p rad. Because
the width of the eye pattern in this example is on the order o f1 UI, the phase error has a negligible effect
on system performance.
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Jitter Tolerance
In general, the noise and imperfect equalization of the transmission system itself introduce much more
jitter than the clock source does. If the jitter, q, of the received data exceeds the receiver’s jitter
i
tolerance, the receiver will begin making errors. When the BERT is recovering its own clock, the
instrument receiver’s jitter tolerance must be greater than the system receiver’s for all waveforms.
Otherwise, the BERT will report an incorrectly high error rate.
It is impossible to check all waveforms. Fortunately, however, if the BERT receiver has a higher jitter
tolerance for sinusoidal jitter at all jitter frequencies, fm, then it has a higher jitter tolerance for all jitter
waveforms.
The maximum data phase jitter,qe max, between the data and the clock that the receiver can tolerate. The
first failure may be the setup time when the decision circuit samples the data with the clock.
Or the clock-recovery circuit may fail to maintain lock if qe is too great. In any case, qe max is generally
between 0.3 and 1.0 UI peak-to-peak. If the system’s qe max is unknown, it can be measured.
The transfer function from q to qe is:
i
çqe/qç=fm/(f2 =f2 )1/2
(Equation 2)
i
m
B
where fm is the frequency of the sinusoidal jitter.
Then the maximum data jitter a receiver can tolerate is qi max=qe max/çqe/q ç
i
Below fB, qI max descends at one decade per decade. Above that frequency (where the clock recovery
can’t follow the data jitter), qi max=qe max.
For proper operation, the BERT receiver’s jitter tolerance curve must lie above that of the system
receiver.
A BERT designed to supply jitter has a sinusoidal generator that modulates the clock phase. Both the
frequency, fm, and the amplitude, A, of the phase are selectable over certain ranges. The range of fm is
from f0 to f4, and the range of the amplitude depends on fm. At low frequencies, the bit-error-rate tester
must generate higher amplitudes than are needed at high frequencies (see following figure).
Amplitude
UI peak-to-peak
A1
A2
f1
f2
f3
f4
Frequency
Figure 5. The range of jitter frequencies and amplitudes that a BERT should generate.
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A BERT designed to measure jitter has a phase demodulator connected to the covered clock. The range of
fm is from f1=10 Hz to f4; the amplitude depends on fm.
The BERT’s jitter generation and jitter measurements specifications should be somewhat higher than the
maximum jitter that a system can typically tolerate. As a result, a BERT with jitter generation can find a
receiver’s qe max by setting fm=f4 and increasing A until the receiver begins to make errors. In addition, the
clock-recovery bandwidth, fB, can be estimated by lowering fm until the jitter tolerance begins to exceed
qe max.
BERT Affects Accuracy
Several BERT characteristics can affect the accuracy of system measurements. For instance, a BERT
transmitter may have a very jittery clock source, such as an open-loop voltage-controlled oscillator. If so,
the system will have a higher error rate or less margin than when the system’s clock source is used.
Measuring the clock-source spectral density and calculation qe rms will uncover this problem.
Another snag may be that a BERT receiver has a very narrowband clock-recovery circuit, such as crystal
controlled phase locked loop. The small fB will probably make the BERT less tolerant of jitter than the
system its testing. In high jitter situations, therefore, the BERT will report a higher bit error rate than the
actual rate. A BERT transmitter with jitter generation can measure its own receiver’s jitter tolerance and
that of the system to see which is greater.
The question of whether a BERT data pattern fairly represents live traffic is more difficult to answer.
Experience indicates that long PRBS patterns (N greater than 14 ) stress the system more than most live
traffic does. But it is rare traffic with unusually stressing patterns that is most interesting. Therefore, the
best users can do is to anticipate these patterns and generate them with fixed patterns from the BERT
transmitter.
============
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Technical article from 5/95 issue of Electronic Design Magazine
Measure Error Rates Quickly and Accurately
By Dan H. Wolaver, Tektronix, Inc.
Abstract
The accurate measurement of the error rate of a digital communication system requires
that a good number of errors be recorded. We show that if n errors are counted, then the
inaccuracy is about 1/ . For example, by recording 400 errors, the inaccuracy is 5%.
n
But if the error rate is very low, the time to accumulate 400 errors can be hours or days.
The measurement time can be reduced by stressing the system under test to produce a
higher error rate. Special graph paper is provided here to plot the error rate as a function
of stress. From this plot, error rate measurements made under stress can be extrapolated
to low error rates at no stress. Measurement time can also be reduce when the task is to
determine an upper bound on the error rate rather than determine the error rate accurately.
We show that if a system is error-free for a period T, then there is 95% confidence the
error rate is less than 3/T. For example, if there are no errors for 1 hour, then 95% of the
time the system tested has an error rate less than 3 per hour.
Example of Error Rate Measurement
Digital communication systems are required to have very low error rates--on the order of 1 error in a
–9
billion bits, or a bit error ratio (BER) of 10 or less. When you must measure such low error rates, you
are faced with a tradeoff; either the test will take a long time or the results will not be accurate. An
example will illustrate a typical situation with such a tradeoff.
Suppose the communication system under test has a bit rate of f = 1.544 Mbit/s, and the BER is required
b
–9
6
–9
to be less than 10 . This limit corresponds to 1.544 ´ 10 ´ 10 = 0.001544 errors per second or 5.56
errors per hour. In general, the error rate r is the bit error ratio times the bit rate:
r = BER ´ f .
(1)
b
The error rate is measured by using either a parity check or a bit-error-rate test set (BERTS). Suppose the
pattern of errors versus time is that shown in Figure 1.
0
1
2
3
4
5
6
7
8
9
10
Time in hours
Figure 1. Shown are random occurrences of errors at an average rate of five per hour. The
distribution here is typical of a Poisson random process.
During the first hour there are seven errors. If the test is terminated at that point, the result is r = 7 / hr >
5.56 / hr, and the system fails. But if the test is extended, there is only one error in the second hour for a
total of eight errors in two hours. Then r = 4 / hr < 5.56 / hr, and the system passes. When there is this
much variation in the measured error rate, you don't have much confidence in the accuracy of the
measurement. We will see that greater confidence requires greater time.
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If a BERT such as the Tektronix GB700/ GB1400 is used to measure the error rate, the current BER is
continually calculated and displayed according to the formulas
r' = n / T
(2)
and
BER' = r' / f = (n / T) / f ,
(3)
b
b
where r' and BER' are the measured estimates of the actual r and BER, T is the elapsed measurement
time, and n is the number of errors counted during T. The variation of r' as T increases is shown in Figure
2.
10
Errors
per hr
One-Sigma Inaccuracy Limits ( within them 68% of the time)
r'
Measured Error Rate r'
5
0
Error times
0
1
2
3
4
5
6
7
8
9
10
T
Measurement Time
in hours
Figure 2. Measured error rate r' is the number of errors n divided by the elapsed time T. As the
elapsed time increases, r' approaches some "actual" rate (about five per hour in this example).
For short measurement times r' varies wildly, but it settles down to about 5 / hr as time increases. When
does r' settle down to the actual error rate r, if ever? Does the system meet the requirement that r < 5.58 /
hr? Does the test have to take upwards of ten hours?
BER Measurement Inaccuracy versus Test Time
The example above raises questions of how close a measured error rate is to the actual error rate and how
long it takes to get there. We can get quantitative answers if we make some assumptions about the
process producing the errors. Errors produced by noise are usually a Poisson process (see the sidebar on
Poisson Errors). This means the errors are unrelated; they do not come in bursts. It also means
conditions are not changing; the temperature is constant, for instance.
A Poisson process presumes an "actual" or average error rate r that can be determined from the process
itself. Our task is to get an estimate r' of this actual rate by measuring n errors in a period T and dividing:
r' = n / T.
(4)
If T is one hour, and if we take many one-hour measurements of n, we will get a range of answers about
some average n . The standard deviation s of the measurements is the rms of the difference from this
average:
N
__
1
s
º
(n - n )2 ,
(5)
N å
i
i =1
where N is the number of measurements. About 68% of the measurements will lie within s of the
average n
.
As shown in the sidebar on Poisson Errors, the standard deviation of n is given in terms of n:
s »
(6)
n
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That is, n is within
of the expected count most of the time (68% of the time). If we take the
n
inaccuracy of the measurement to be s as a fraction of n, then
Inaccuracy
= s / n » 1/
.
(7a)
n
68%
This relationship is plotted in Figure 3 (the curve for 68% confidence).
Inaccuracy
in %
30
95% Confidence
20
68% Confidence
10
0
10000
100
1000
10
Number of errors measured n
Figure 3. Inaccuracy error-rate measurement can be expressed as a function of the number of
errors measured. A confidence of 68 percent means that if the test is repeated, the measured error
rate will be closer to the actual error rate than inaccuracy indicated 68 percent of the time. For 95
percent confidence, the inaccuracy is twice as large.
As an example, suppose it is desired that the accuracy be 0.10, or 10%. Then from Eq. (7a) the test must
continue until n = 100. If the time to collect 100 errors turned out to be T = 19 hr, then r' = 100 / 19 hr =
5.26 / hr, and this is within 10% of the actual error rate r. That is, r is inferred to lie between 5.26 – 0.526
= 4.734 / hr and 5.26 + 0.526 = 5.78 / hr (with a confidence of 68%). Because of the statistical nature of
the measurement, n = 100 can be more than 10% away from the expected measurement, but 68% of the
time it will be less than 10% away.
You can increase your confidence level by using 2s. The measured n = 100 is within 2s (or 20% here) of
the expected count 95% of the time (see the other curve in Figure 3). In the example of r' = 5.26 / hr, r
is inferred to lie between 5.26 – 1.052 = 4.208 / hr and 5.26 + 1.052 = 6.312 / hr with a confidence of
95%. You are more confident the inaccuracy won't be exceeded, but the inaccuracy is twice as large.
To maintain a confidence of 95% (the higher curve in Figure 3) and still have an inaccuracy of 10%, you
need to count more errors. If 2s is to be 10% of n, then s is 5% of n, or s / n = 0.05. From Eq.(6) this
gives 1 / n = 0.05, or n = 400. The general expression for the inaccuracy with 95% confidence is
Inaccuracy
= 2s / n » 2/
.
(7b)
n
95%
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Testing for an Upper Limit on Error Rate
–9
If a communication system is required to have a BER less than 10 , the system design usually provides a
–12
couple dB of margin. This margin can make the nominal error rate on the order of 10 , which is an
average of only one error a week for f = 1.544 Mbit/s! It is clearly impractical to measure such a low
b
error rate accurately. But accuracy is not needed here––only some confidence that the error rate is less
–9
than 10 . We will see that determining an upper bound on an error rate takes much less time than
determining the error rate accurately.
The proposed method for determining an upper bound on an error rate is to require the system under test
to be error-free for a measurement period T. The longer T is, the lower the error rate bound. Suppose you
want to be sure that the actual error rate of some system is less than a specified error rate of r = 5.56 / hr.
Then you must choose T so an error rate of r = 5.56 / hr or greater will have at least one error in the
period T. But because of the statistical nature of the measurement, this can't be absolutely guaranteed no
matter haw large you make T.
You must settle for some confidence level (say 90%) that the error rate is less than r. So choose T so r =
5.56 / hr will fail the test 90% of the time. That is, choose T so the probability of measuring n = 0 errors
is only 10% when the error rate is at the limit r. The sidebar on Poisson Errors gives the probability of
measuring n = 0 as
–rT
p(0) = e
.
(8)
Then set p(0) = 0.10 or 10% and solve for T:
- ln (0.10) 2.3
T =
=
.
(9)
r
r
For r = 5.56 / hr, this gives T = 0.414 hr. If the system is error-free for 0.414 hour (25 minutes), you are
90% confident that the error rate is less than r = 5.56 / hr.
In general, for a confidence level C that the error rate is less than r, the error-free period is given by
- ln (1- C)
T =
.
(10)
r
For example, for C = 0.99 and r = 5.56 / hr, then T = 0.827 hr. By doubling the test time you have
increased the confidence from 90% to 99%. The tradeoff is up to you.
Reduced Test Time by Stressing
Whether the objective is to measure the error rate accurately or to determine an upper bound on the error
rate, you can decrease the measurement time dramatically by stressing the system under test. The stress
produces a higher error rate, and the higher error rate can be measured more quickly. Then if the error
rate as a function of stress is known, you can extrapolate to the error rate the system would have when it
is not stressed.
The error rate is a function of the distance S of the signal from the decision threshold compared with the
level of noise. If the noise exceeds S at the decision time, there is an error. Therefore the BER is the
probability the noise exceeds S. If the noise is Gaussian (or "normal distribution") with an rms value of
N
, then the BER is given by
rms
2
rms
2
¥
ò
S
¥
1
1
BER =
e- 0.5x / N dx =
e-0.5 y dy
ò
S / Nrms
Nrms
2
p
2p
(11)
2
S / Nrms
1
=1-
e-0.5 y dy =1- cnorm(S / Nrms
)
ò
0
2
p
The second integral is the result of the substitution y = x / N . The function "cnorm" is the cumulative
rms
normal distribution. For an evaluation of this function see, for example, "Probability and Statistics" in
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Standard Mathematical Tables published by the Chemical Rubber Co, or use the software product
Mathcad produced by MathSoft.
It is usually convenient to measure signal strength and noise in dB. Let the signal-to-noise ratio in dB be
defined as
SNR = 20 log(S / N
).
(12)
rms
Then with Equation (11) we can find BER as a function of SNR. This is plotted in Figure 4. In Figure 4a
the BER axis is a log scale. In Figure 4b the BER axis has a specially distorted scale so the plot appears
as a straight line. This will help in determining whether noise is Gaussian, and it will help in
extrapolating data. Suppose a system has a SNR of 18 dB. According to Figure 4, the corresponding bit
-16
error ratio is 10 . At a baud of 1 Gbit/s, this would yield an error only once every 4 months on average.
To get an estimate of this error rate in a reasonable time, testing with stress is necessary.
1
2
10
10
10
10
2
3
BER
4
10
3
10
5
10
10
BER
6
7
8
9
4
5
10
10
10
10
10
6
7
10
11
12
13
14
15
16
10
10
10
10
10
10
10
8
9
10
10
10
10
12
10
10
10
14
16
7
10
10
7
8
9
10 11 12 13 14 15 16 17 18
SNR (dB)
8
9
10
12 13
14 15
16
17
11
18
(a)
SNR (dB)
(b)
Figure 4. Bit-Error-Rate (BER) is plotted here as a function of the signal-to-noise ratio (SNR),
where SNR is S/Nrms in decibels (electrical), S is the distance from the signal (1 or 0) to the
decision threshold and Nrms is the rms value of the Gaussian noise introduced by the first receiver
state (a). In (b), the log scale was distorted, so the plot is a straight line.
The stress that we propose is attenuation of the received signal S. Most of the system noise arises in the
input stage of the data receiver, and the attenuator won't affect this noise. Then if there is no AGC, the
attenuator reduces S. If there is an AGC, S is held constant and the noise increases. In any case, the ratio
of S to N
changes with the attenuation; 6 dB of electrical attenuation decreases the signal-to-noise ratio
rms
by 6 dB. In general, the signal-to-noise ratio with stress is
SNR = SNR – Attenuation, (13)
0
where SNR is the signal-to-noise ratio without stress (attenuator set to 0 dB).
0
In order to properly extrapolate data taken with stress, we need to know what a plot of BER versus
Attenuation looks like for a given SNR . Suppose that SNR is 18 dB. Then for Attenuation = 0 the
0
0
- 16
SNR is also 18 dB, and from Figure 4 we find BER = 10
As the Attenuation is increased to 6 dB, then SNR is reduced to 18 – 6 = 12 dB. According to Figure 4,
(see point at Attenuation = 0 in Figure 5).
-5
this corresponds to BER = 3.5´ 10 (see point at Attenuation = 6 dB in Figure 5). The complete plot of
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BER vs. Attenuation appears as a straight line because the BER scale is again distorted. The line here is
for the case SNR = 18 dB. For other values of SNR , the plot would fall parallel to the line in Figure 5.
0
0
Remember that we are talking about electrical attenuation here; 1 dB of optical attenuation is worth 2 dB
of electrical attenuation.
2
10
3
10
BER
4
10
5
10
6
10
7
10
8
10
9
10
10
10
12
10
14
10
16
10
0
1
2
3
4
5
6
7
8
9
10 11
Attenuation (dB)
Figure 5. BER is plotted as function of electrical-signal attenuation for the case of a system with
BER=10-6 for no attenuation. That is, the SNR0 for no attenuation is 18 dB. Then, SNR with
attenuation is 18 dB minus attenuation, and BER follows from Figure 4.
It isn't practical to plot a curve such as that in Figure 5; it would take too long to plot the points for low
-5
BER. But if the noise is known to be Gaussian and the BER is found to be 3.5´ 10 for 6 dB of
–16
attenuation, then the BER can be inferred to be 10
for no attenuation. It is actually better to plot two
points for two attenuations and extrapolate to zero attenuation. An example will show how this
extrapolation is done.
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Example 1
A 44.736-Mbit/s system seems to have a very low error rate; in a five-minute test no errors occurred. It is
decided to use stress to estimate the BER with no stress. When 5 dB of electrical attenuation is placed in
-4
the signal path, 13,400 errors are measured in one second––a BER of 13400 / 44736000 = 3´ 10 . Using
graph paper like that provided at the end of this article, plot a point at Attenuation = 5 dB and BER = 3´
-4
10 , as in Figure 6. Then the electrical attenuation is reduced to 3 dB, and 16,100 errors are measured in
-6
60 seconds. This is a BER of 16100 / (60 ´ 1544000) = 6´ 10 , which is also plotted in Figure 6. A
-10
-
straight line through the two points intersects the BER axis at 10 , so the unstressed BER would be 10
10
(one error every 3.7 minutes on average.)
3
10
BER
Example 1
4
10
5
6
10
10
7
8
10
10
Example 2
9
10
10
10
12
10
14
16
10
10
0
1
2
3
4
5
6
7
Attenuation (dB)
Figure 6. In this extrapolation, we find BER for no attenuation from BER measurements with two
attentuations. In the first example, many errors were measured, resulting in tight control of the
extrapolation. In the second, too few errors were measured, creating uncertain BER estimates
(see the bars) and a sloppy extrapolation.
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Note that the line through the points in Figure 6 has about the same slope as the dashed lines. This
indicates the noise is about Gaussian. As the slope of the plotted line is closer to that of the dashed lines,
the noise process is closer to Gaussian, and the extrapolation is more reliable. Departure of the slope
from the Gaussian could be due to (a) too few errors measured, leading to inaccurate BER values, (b) the
presence of a non-Gaussian noise mechanism such as error bursts, or (c) significant noise in the system
before the attenuator. (Noise coming into the receiver with the signal is assumed to be less than that
introduced by the first stage in the receiver.)
Whether or not the slope is the expected one, confidence in the extrapolation can always be increased by
taking time to plot out the BER-versus-Attenuation curve once down to very low BER. Thus it may take
a day or so to test the first system, but subsequent systems can then be tested quickly with the stress-and-
extrapolate method.
It is important to measure enough errors that the inaccuracy is low and the extrapolation is valid. Because
more than 10,000 errors were measured each time, the inaccuracy of the BER measurement is less than
1% [see Equation (7a)]. This is small enough that the extrapolated results are accurate, even given the
magnification effect of extrapolation. To illustrate the importance of measuring enough errors, we will
look at an example where measuring too few errors leads to uncertain results.
Example 2
A 1.544-Mbit/s system is stressed with 6 dB of electrical attenuation. In a one-second interval 54 errors
-5
are measured––a BER of 54 / 1544000 = 3.5´ 10 . But with only 54 errors, the inaccuracy is 14% (see
-5
-5
Figure 3 for 68% confidence). Therefore the BER lies between 3.0´ 10 and 4.0´ 10 . This uncertainty
is indicated by plotting a bar at 6 dB in Figure 6. Then the electrical attenuation is reduced to 4 dB, and
-7
37 errors are measured in 60 seconds. This is a BER of 37 / (60 ´ 1544000) = 4´ 10 . But with 37
-7
-7
errors, the inaccuracy is 16%, and the BER lies between 3.35´ 10 and 4.65´ 10 . This is also plotted
as a bar in Figure 6. Straight lines passing through the two bars sweep out the gray region shown and
-15
-13
intersect the BER axis anywhere from 2´ 10
to 1.5´ 10
.
The large uncertainty of the extrapolated results in this example is mostly due to the few number of errors
measured. A good rule is to measure at least 1000 errors for each point. Another guideline is to make the
larger attenuation at least 1.5 times the smaller; a greater separation between the two points allows better
extrapolation. Also, use as little attenuation as possible so the extrapolation distance is not so great (this
involves a trade-off with greater test time).
Stressing can also be used to reduce the time required to show that the unstressed BER is below some
specified value. The following example will show how the graph paper provided at the end of the article
can be used in this way.
Example 3
-9
A 1.544-Mbit/s system is to have a BER no more than 10 . This corresponds to an error rate of r =
-9
-9
1544000 ´ 10 = 0.001544 errors per second. For a confidence C = 95% that the BER of the system is
less than 10 , it must test error-free for T = 3 / r = 1943 seconds, or 32 minutes [see Equation (10)].
This test time can be shortened by using stressing.
-9
Suppose a system was just on the limit, with an unstressed BER of the specified 10 . Make a plot of
-9
BER versus Attenuation by starting at BER = 10 for Attenuation = 0, and draw a straight line parallel to
-9
the dashed lines, as in Figure 7. We see that 3 dB of electrical attenuation would raise a BER of 10 to
-5
10 , or a stressed error rate of r = 15.44 errors per second. So we stress the system with 3 dB of
s
attenuation and test it for T = 3 / r = 0.194 seconds. If there are no error in that time, then we have 95%
s
s
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-5
confidence that the stressed error rate is less than 10 . By extrapolation, we are 95% confident the
-9
unstressed BER is less than 10 .
4
10
BER
Example 3
5
10
6
10
Example 4
7
10
8
10
9
10
10
10
12
10
(elec)
2.5 (opt)
0
0
1
0.5
2
1
3
1.5
4
2
5
Attenuation (dB)
Figure 7. This plot determines the attenuation necessary to turn a test for BER=10-9 with no stress
into a test for BER=10-5 with stress (the third example in text). Draw a straight line from BER=10-9
-5
at no attenuation parallel to the dashed lines until it rises to BER=10 . The electrical attenuation at
this point is 3 dB. In the fourth example in the text, 1 dB of optical attenuation is needed to turn a
test for BER=10-10 with no stress into a test for BER=2 x 10-7 with stress.
In this case stressing has reduced the test time by a factor of 10,000. This is probably more reduction than
is needed. It would be better to stress the system less so the test conditions are not so greatly different
than the normal conditions. Less stress increases the test time, but that could be afforded here.
Example 4
-10
A 51.84-Mbit/s optical system is to have a BER no more than 10 . This corresponds to an error rate of
-10
r = 51840000 ´ 10
= 0.005184 errors per second. If it tests error-free for T = 3 / r = 579 seconds, we
-10
are 95% that the BER is less than 10 . We will shorten the test time by using stressing.
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-10
-10
for Attenuation =
Make a plot of BER versus Attenuation for SNR = 10
by starting at BER = 10
0
0, and draw a straight line parallel to the dashed lines, as in Figure 7. We will use a smaller stress than in
Example 3. An optical attenuation of 1 dB (equivalent to 2 dB of electrical attenuation) would raise the
-7
-7
BER to 2´ 10 , or a stressed error rate of r = 51840000 ´ 2´ 10 = 10.37 errors per second. So for
s
95% confidence, we stress the system with 1 dB of optical attenuation and test it for T = 3 / r = 0.289
s
s
seconds. If there are no errors in that time, then we have 95% confidence that the stressed error rate is
-7
-10
less than 2´ 10 . By extrapolation, we are 95% confident the unstressed BER is less than 10 . In this
case stressing has reduced the test time by a factor of 2000.
Summary
The inaccuracy of an error rate measurement is not due to any fault of the measurement equipment.
Rather the inaccuracy come from incomplete knowledge when too few errors are observed. Therefore the
accuracy can be improved only by taking more time to do the measurement. A good rule of thumb is that
the inaccuracy is the reciprocal of the square root of the number of errors counted. For example, the
inaccuracy is 5% if 400 errors are counted.
Determining that an error rate is below some limit takes less time than determining the error rate
accurately. If the system under test is error-free of a period T, then we can say the error rate is probably
below some rate r. An easy rule to remember is that for 95% confidence that the error rate is less than r,
the system must test error-free for T = 3 / r.
The time to measure a low error rate can be reduced by stressing the system with a signal attenuator.
Measure the higher error rate with stress quickly, and extrapolate to the unstressed error rate. (This
method assumes Gaussian noise and insignificant noise present before the attenuator.) Use the special
graph paper provided at the end of this article help in the extrapolation; you are free to copy it. Take care
to observe the guidelines for stressing in order to get good results.
It is worth taking the time to understand the properties of error rates. A small investment of time here can
pay off in big savings in reduced test time.
================
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Sidebar article to Measure Error Rates Quickly and Accurately
Poisson Error Process
A Poisson process is one in which events are not dependent on each other, and conditions causing the
events don't change with time. Raindrops hitting a skylight is an example of a Poisson process. The
impact of one raindrop doesn't affect the arrival time of another. If we know the average rate r of a
Poisson error process, then we have completely characterized it. In particular, if errors are measured for a
period T, the probability of measuring n errors is given by
(rT)n
p(n) =
e- rT
.
n!
(For a proof of this, see Probability, Random Variables, and Stochastic Processes by Papoulis, McGraw-
Hill, 1965.)
For example, for r = 5 / hr and T = 1 hr, the probability of measuring n errors in one hour is plotted in
Figure S-1a. It is most probable that n = 4 or 5 errors will be measured. The probabilities for all the n
sum to one.
If the one-hour test is repeated many times, the mean (or expected) number of errors is
µ = rT.
For the case r = 5 / hr and T = 1 hr, on average µ = 5 errors will be measured. As the test is repeated
many times for the same r and T, the standard deviation of the measurement n is given by
s
=
m
= rT . (see Papoulis for a proof of this).
In this case s = 5 = 2.24, which is 45% of m (see Figure S-1b).
0.06
0.18
0.16
0.05
0.14
0.12
0.1
0.04
s
m
= 0.45
p
(n)
s
m
= 0.14
p
(n)
0.03
0.02
0.01
0
0.08
0.06
0.04
0.02
0
s
s
s
s
m
5
m
0
1
2
3
4
6
7
8
9
10 11 12 13
0
10 20 30 40 50 60 70 80 90 100 110 120 130
n
n
(S-1a)
(S-1b)
Figure S-1a. Probability p(n) of n errors in one hour for an average of 5 per hour. The error
process is Poisson. About 68% of the time n is no more than ss away from the mean value mm= 5.
Figure S-1b. Probability p(n) of n errors in ten hours for an average of 5 per hour. Because the
mean number of errors is larger (mm= 50), ssis now smaller in relation to mm
.
If the measurement time is increased to T = 10 hr, then µ = 5 ´ 10 = 50 errors, and the curve of p(n)
becomes much "tighter", as shown in Figure B. Now s = 50 = 7.07, which is only 14% of m. About
68% of the area under the curve lies between n = m - s and m + s, indicating that 68% of the time n will
lie in this range. If we consider 68% to be "most of the time," then we can write the "bounds" on n as
µ - s < n < µ + s.
For r = 5 / hr and T = 10 hr, the range is ±14%, which is better than the range of ±45% for T = 1 hr.
However, the tighter range came at the cost of ten times the test time.
The estimated error rate r' = n / T is correspondingly "bounded" by
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(µ - s) / T < r' < (µ + s) / T
or
r - r / T < r'< r + r / T .
These two "bounds" are shown by the two curves in Figure S-2. The measured error rate r' is seen to lie
between them most of the time. As T increases, the bounds get closer to r = 5 / hr, but there will always
be some deviation of r' from r. Therefore the "actual" error rate r can never be known in practice; it
would take an infinite time to measure r.
The standard deviation of the error measurement n is
exactly in practice, we must use the estimates µ » n and r » r' to get the estimate
» n = r'T .
s
=
m
= rT . But since µ and r can't be known
s
102
103
104
105
BER
106
10 7
10 8
10 9
10 10
1012
1014
1016
(elec)
(opt)
0
1
0.5
2
1
3
1.5
4
2
5
2.5
6
3
7
3.5
8
4
9
4.5
10
5
11
5.5
0
Attenuation (dB)
Figure S-2. Specially distorted scale so plots of BER versus signal Attenuation (electrical or
optical) are straight lines (parallel to the dashed lines) when the noise is Gaussian.
=============
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Biography
Dan Wolaver is director of research and development at Tektronix/BTT, Inc. He received a PhD in
electrical engineering from MIT in 1969. For ten years he worked for Bell Labs on digital
communications systems, and he taught at Worcester Polytechnic Institute for eleven years. He is the
author of Phase-Locked Loop Circuit Design.
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Remote Commands
This chapter explains the syntax used by the GB1400 remote command language, and
defines all set and query commands. In addition, commands are listed and briefly
described in both alphabetical and functional order.
Type of Commands
IEEE 488
Starts on page
12
19
26
30
33
37
43
44
54
64
71
77
81
83
86
88
Pattern and Word
GPIB and RS-232
Shared Commands
Clock Source and Frequency Setup
Output (Clock and Data) Setup
Error Injection
Results Retrieve
Input Setup
Error Detector and History Setup
Test Setup
Window Setup
Print Setup
Audio Beeper Setup
Date & Time
Commands specific to 1 MB Option
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Remote Commands
Overview
This section defines the GB1400 command syntax including command types, parameter
types, delimiters used between command elements, and terminators used at the end of
command lines.
Symbols
The table below shows the symbols used in this chapter to describe GB1400 commands
and responses.
Symbol
<CR>
Meaning
Carriage return (ASCII decimal 13).
Line Feed (ASCII decimal 10).
<LF>
<EOI>
End or Identify, a message terminator signal specified
in ANSI/IEEE Std. 488.2-1987
<ui>
<NR1>
Unsigned integer in range 0 through 65,535
Signed integer value.
<NR2>
Floating point value, without an exponent.
Floating point value, with an exponent.
<NR3>
<non-decimal numeric>
A non-decimal integer in the range 0 - 255 (decimal)
with leading "#H" (hexadecimal), "#Q" (octal), or "#B"
(binary). Examples:
Hexadecimal:
Octal:
#HFF
#Q377
Binary:
#B11111111
<qstring>
A quoted string; that is a character string with
beginning and ending quotes.
[ ]
|
Enclosed argument is required.
Exclusive OR. For example the argument [a | b | c]
means that you must include one and only one of the
following parameters: a, b, or c.
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Remote Commands
Command Types: Set and Query
There two basic types of GB1400 commands: set commands and query commands. Set
commands are used to make setup changes or to cause a status change, for example to
start or stop a test. Query commands ask the instrument to respond with the contents of
a status register or the value of a given setup parameter.
GB1400 commands may have only a query form or only a set form, however most
commands have both. When a command has both a set and query form, the name or
"mnemonic" used for the query form will be identical to its corresponding set command
form, except for an added "?". For example the following are the mnemonics for the set
and query form of the data threshold command:
q DATA_THRES
(set command)
q DATA_THRES?
(query command)
Note that in this User's Guide, query commands may be referred to as simply "queries",
while set commands may be referred to as simply "commands".
Command Line Format
Command Names (Headers)
Every GB1400 command starts with a command header. Headers are character strings
that contain either an entire command name, or a legal abbreviation of a command name.
Legal command name abbreviations must include the leading significant characters in the
command name. For example, in the save_word command only the first two letters are
significant. Therefore the save_word command header may contain any of the following
character strings:
save_word
save_wor
save_wo
save_w
save_
save
sav
sa
The minimum abbreviation for each command name is identified in the Command
Descriptions section later in this chapter. The use of command abbreviations is often
useful when you are operating a GB1400 Generator or Analyzer manually from a
terminal. However when including command names in control programs it is
recommended that the full command names always be used as command headers. This
improves readability and reduces the chance that a control program will be incompatible
with future versions of GB1400 software which may include additional commands.
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Remote Commands
Command Line Rules
The following rules summarize the basic syntax of GB1400 commands:
Command Lines: A given command line may contain one or multiple commands. If a
command line contains multiple commands, commands will be separated by a ";"
(semicolon).
Command Line Terminator
RS-232C Interface: Command lines issued to the instrument should be terminated
by a simple carriage return (CR). Responses generated by the instrument will be
terminated as specified by the user in the RS-232 EOL menu function, that is CR, LF,
CR/LF or LF/CR.
GPIB Interface: Command lines issued to the instrument can be terminated by
either EOI or EOI/LF. Responses generated by the instrument will be terminated as
specified by the user in the GPIB menu function, that is either EOI or EOI/LF.
Maximum Number of Characters per Line: Command lines may contain a
maximum of 80 characters before the terminator.
Command Headers (Names): Each command must start with a header. This header
must contain either the full name of the command, or an abbreviation containing at least all
of the leading significant characters identified for that command name. In addition, query
commands must end with a "?".
Upper and Lower Case: All characters in a GB1400 command line may be entered in
either upper or lower case.
Arguments: Commands may include one or more arguments (parameters) following the
header. The first argument following the header must be separated from the header by
one or more blank characters (spaces). Subsequent arguments must be separated from
previous parameters using commas.
Blank Characters (Spaces): One or more spaces are required between the command
header and first parameter (if any). Otherwise spaces are ignored by the GB1400 and
may be used on a command line between headers, parameters, or required separators for
readability.
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Remote Commands
Setting Arguments Outside of Legal Ranges
If you issue a set command with an argument value that is outside the allowed range for
that argument, then the instrument will reject the command.
Numeric Responses
If the response to a query command is a number, then it will be specified as one of the
following types:
Type
Description
<NR1>
<NR2>
<NR3>
decimal integer (e.g., 8)
decimal real number without exponent (e.g., 2.00)
decimal real number with exponent (e.g., 700.0E+6)
<Non-decimal numeric> non-decimal number with leading "#H" (hexadecimal), "#Q"
(octal), or "#B" (binary).
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Remote Commands
Command Examples
The following are some typical GB1400 set and query command examples:
Command
clock_freq?
Action or Response
Returns the current output clock frequency setup of
the Generator or the measured input clock frequency
of the Analyzer
word_memory?
Returns the saved word patterns in all 10 word
memory locations.
word_memory? 7
Returns the saved word pattern in word memory
location 7.
word memory 9, 16, #Haa, #H23
Sets the 16 bits of the word pattern stored at location
9 to the bit sequence represented by AA23
hexadecimal.
word_bits 8, #Q307
recall_word 7
Sets the first eight bits of the current active pattern to
the bit sequence represented by 307 octal.
Recalls the word pattern saved in location 7 and
makes it the current active pattern.
word_mem_len 6 , 16
Sets the length of the word pattern stored in location
6 to 16 bits.
view_angle?
view_angle 3
rs_prompt "700"
all_mem?
Returns the current display view angle setup.
Sets the view angle to 3.
Sets the terminal display prompt to "700".
Returns the word patterns saved in all 10 word
memory locations.
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Remote Commands
Command Summary – Alphabetical
The following is a listing of all GB1400 Generator and Analyzer commands and the page
number of their full description.
Page
*cls......................................................................................................C-12
*ese [n]................................................................................................C-12
*ese?...................................................................................................C-13
*esr?....................................................................................................C-13
*idn?....................................................................................................C-13
*lrn? ....................................................................................................C-14
*opc.....................................................................................................C-14
*opc?...................................................................................................C-14
*rst......................................................................................................C-15
*sre [n] ................................................................................................C-15
*sre?....................................................................................................C-16
*stb?....................................................................................................C-16
*tst?.....................................................................................................C-17
*wai.....................................................................................................C-17
all_mem? .............................................................................................C-30
amplitude [v] ........................................................................................C-37
amplitude?............................................................................................C-37
audio_rat_dn ........................................................................................C-83
audio_rat_up ........................................................................................C-83
audio_rate [v].......................................................................................C-83
audio_rate? ..........................................................................................C-84
audio_vol [v] ........................................................................................C-84
audio_vol? ............................................................................................C-84
audio_vol_dn........................................................................................C-85
audio_vol_up........................................................................................C-86
auto_mode ...........................................................................................C-64
auto_sample [n]....................................................................................C-65
auto_search [auto | off | disab]...............................................................C-63
auto_search?........................................................................................C-63
auto_thresh [n] .....................................................................................C-66
auto_width ..........................................................................................C-66
byte_block [a], [i], [b1], ..., [bn] .............................................................C-89
byte_block? [a].....................................................................................C-90
byte_delete [a], [i] ................................................................................C-91
byte_edit [a], [b1] .................................................................................C-92
byte_edit? [a].......................................................................................C-92
byte_fill [i], [b1], [b2], ..., [bn]................................................................C-93
byte_insert [a], [i], [b1], ..., [bn].............................................................C-93
byte_length [m], [n] ..............................................................................C-94
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Remote Commands
byte_length?.........................................................................................C-94
byte_mode ...........................................................................................C-95
byte_sync [n] (Analyzer only)...............................................................C-96
byte_sync? (Analyzer only) ................................................................C-96
clock_amp_dn......................................................................................C-37
clock_amp_up......................................................................................C-37
clock_ampl [v]......................................................................................C-38
clock_ampl? .........................................................................................C-38
clock_freq [v].......................................................................................C-33
clock_freq? ..........................................................................................C-33
clock_freq? ..........................................................................................C-45
clock_memory [m], [f]..........................................................................C-34
clock_memory? ....................................................................................C-33
clock_memory? [m]..............................................................................C-34
clock_off_dn........................................................................................C-38
clock_off_up........................................................................................C-38
clock_offset [v] ....................................................................................C-39
clock_offset?........................................................................................C-39
clock_source [int|ext]............................................................................C-34
clock_source? ......................................................................................C-34
clock_step [v].......................................................................................C-35
clock_step? ..........................................................................................C-35
clock_stp_dn........................................................................................C-35
clock_stp_up........................................................................................C-35
clock_term [neg_2v | gnd | ac|pos_3v] ...................................................C-54
clock_term? .........................................................................................C-54
data_amp_dn........................................................................................C-39
data_amp_up........................................................................................C-39
data_ampl [v] .......................................................................................C-40
data_ampl?...........................................................................................C-40
data_del_dn..........................................................................................C-55
data_del_up..........................................................................................C-55
data_delay [v] ......................................................................................C-56
data_delay?..........................................................................................C-56
data_invert [on|off]...............................................................................C-19
data_invert? .........................................................................................C-19
data_off_dn..........................................................................................C-40
data_off_up..........................................................................................C-40
data_offset [v]......................................................................................C-41
data_offset? .........................................................................................C-41
data_pattern [prbs | word | rdata]...........................................................C-19
data_pattern? .......................................................................................C-20
data_term [neg_2v | gnd | ac | pos_3v]...................................................C-57
data_term?...........................................................................................C-57
data_thr_dn..........................................................................................C-58
data_thr_up..........................................................................................C-58
data_thres............................................................................................C-58
data_thres? ..........................................................................................C-59
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Remote Commands
date ["yyyy-mm-dd"].............................................................................C-86
date?....................................................................................................C-86
disp_select [total | window | test] ...........................................................C-67
disp_select?..........................................................................................C-67
edit_begin [n] .......................................................................................C-97
edit_cntrl? ............................................................................................C-98
edit_end [n]..........................................................................................C-98
error_rate [off|ext|rate_3|rate_4|rate_5|rate_6|rate_7] ............................C-43
error_rate?...........................................................................................C-43
error_reset...........................................................................................C-67
error_single ..........................................................................................C-43
gpib_address [v] ...................................................................................C-26
gpib_address?.......................................................................................C-26
gpib_bus [off_bus | talk_listen ] .............................................................C-26
gpib_bus?.............................................................................................C-27
header [on | off]....................................................................................C-31
header?................................................................................................C-31
histry_bits?...........................................................................................C-68
histry_clear ..........................................................................................C-68
histry_phase? .......................................................................................C-69
histry_power?.......................................................................................C-69
histry_stat?...........................................................................................C-69
histry_sync?.........................................................................................C-70
logo?....................................................................................................C-31
offset [v]..............................................................................................C-42
offset? .................................................................................................C-42
options?................................................................................................C-32
prbs_length [v] .....................................................................................C-20
prbs_length?.........................................................................................C-20
print_enable [on|off]..............................................................................C-81
print_enable?........................................................................................C-81
print_port [ parallel | gpib | serial ]..........................................................C-81
print_port?............................................................................................C-82
print_string ["s"]....................................................................................C-82
rdata_del_dn ........................................................................................C-59
rdata_del_up ........................................................................................C-59
rdata_delay [v] .....................................................................................C-60
rdata_delay?.........................................................................................C-60
rdata_term [neg_2v | gnd | ac | pos_3v]..................................................C-60
rdata_term?..........................................................................................C-60
rdata_thr_dn.........................................................................................C-61
rdata_thr_up.........................................................................................C-61
rdata_thres [v]......................................................................................C-61
rdata_thres?.........................................................................................C-62
recall_freq [m] .....................................................................................C-36
recall_mark [m1_8|m1_4|m1_2|m3_4|m7_8] ..........................................C-99
recall_prom [n]....................................................................................C-99
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Remote Commands
recall_word [m]....................................................................................C-21
res_bits? ..............................................................................................C-45
res_cur_rate?.......................................................................................C-45
res_dm?...............................................................................................C-46
res_dm_per?........................................................................................C-46
res_efs?...............................................................................................C-46
res_efs_per?........................................................................................C-47
res_elapsed? ........................................................................................C-47
res_errors?...........................................................................................C-47
res_es? ................................................................................................C-48
res_es_per? .........................................................................................C-48
res_los? ...............................................................................................C-48
res_pha_es?.........................................................................................C-49
res_ses?...............................................................................................C-49
res_ses_per?........................................................................................C-49
res_start?.............................................................................................C-50
res_stop? .............................................................................................C-50
res_sync?.............................................................................................C-50
res_tes?...............................................................................................C-51
res_tes_per? ........................................................................................C-51
res_tot_rate?........................................................................................C-51
res_us?................................................................................................C-52
res_us_per? .........................................................................................C-52
rs_echo [on|off]....................................................................................C-27
rs_echo? ..............................................................................................C-27
rs_pmt_lf [on|off] .................................................................................C-27
rs_pmt_lf?............................................................................................C-28
rs_prompt [s]........................................................................................C-28
rs_xon_xoff [on|off]..............................................................................C-28
rs_xon_xoff?........................................................................................C-29
save_freq [m].......................................................................................C-36
save_word [m] .....................................................................................C-21
sync?...................................................................................................C-70
test_discard..........................................................................................C-71
test_length [t].......................................................................................C-71
test_length?..........................................................................................C-71
test_mode [untimed|timed|repeat]...........................................................C-72
test_mode?...........................................................................................C-72
test_prev [current|previous]...................................................................C-72
test_prev? ............................................................................................C-73
test_print..............................................................................................C-73
test_report [eot|on_error|both|none] ......................................................C-73
test_report?..........................................................................................C-74
test_squelch [on|off] .............................................................................C-74
test_squelch?........................................................................................C-74
test_state [run|stop] ..............................................................................C-75
test_state?............................................................................................C-75
test_thres [v]........................................................................................C-76
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Remote Commands
test_thres? ...........................................................................................C-76
time [s] ................................................................................................C-87
time?....................................................................................................C-87
total_bits?.............................................................................................C-52
total_error? ..........................................................................................C-53
total_rate?............................................................................................C-53
total_time? ...........................................................................................C-53
tse [v] (Analyzer Only) ........................................................................C-17
tse? (Analyzer Only)............................................................................C-17
tsr? (Analyzer Only) ............................................................................C-18
view_angle [v]......................................................................................C-32
view_angle?.........................................................................................C-32
win_bit_len [v] .....................................................................................C-77
win_bit_len?.........................................................................................C-77
win_bits?..............................................................................................C-77
win_error? ...........................................................................................C-77
win_mode [bits|sec]..............................................................................C-78
win_mode?...........................................................................................C-78
win_prev [current|previous]...................................................................C-78
win_prev? ............................................................................................C-78
win_rate?.............................................................................................C-79
win_report [on|off]................................................................................C-79
win_report?..........................................................................................C-79
win_sec_len [s]....................................................................................C-80
win_sec_len? .......................................................................................C-80
win_time? ............................................................................................C-80
word_bits [l], [b1 | b2]...........................................................................C-21
word_bits? ...........................................................................................C-22
word_length [l] .....................................................................................C-22
word_mem_len [m], [l] .........................................................................C-22
word_mem_ord [m], [msb | lsb].............................................................C-23
word_mem_ord? ..................................................................................C-23
word_mem_ord? [m] ............................................................................C-23
word_memory [m], [l], [b1], [b2] ...........................................................C-24
word_memory? [m] ..............................................................................C-24
word_memory? ...................................................................................C-25
word_order [msb | lsb] ..........................................................................C-25
word_order?.........................................................................................C-25
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Remote Commands
Command Descriptions
The following section defines each GB1400 set and query command. Unless noted
otherwise, the following conventions will be followed in the command descriptions in later
sections of this chapter:
Command Headers: Command headers will be shown using the entire command name
in lower case. For legal abbreviations, see the Command Summary – Alphabetical
section earlier in this Chapter.
Set and Query Command Pairs:
Commands that have both forms will be listed under the set command name. For
example the data threshold set and query commands above will be listed under the name
DATA_THRES.
Common and Proprietary GPIB Commands
The following GPIB "common commands" defined in ANSI/IEEE Std. 488.2-1987.
*cls
Clear Status. This set command clears the Standard Event Status Register (SESR) and
the event status bit (ESB) in the Status Byte Register (SBR). In addition it puts the
instrument into the Operation Complete Command Idle State and the Operation Complete
Query Idle State.
Min. Abbr.
Example
*cls
*cls
*ese [n]
Event Status Enable. This command sets the Event Status Enable Register (ESER) to
the bit sequence corresponding to n, where n is a decimal number in the range 0 to 255.
Min. Abbr.
Argument
Example
*ese
n: 0 to 255 decimal.
*ese 255
(sets the ESER to 11111111 binary)
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*ese?
Event Status Enable (Query). Returns a decimal number in the range 0 to 255
corresponding to the contents of the Event Status Enable Register (ESER).
Min. Abbr.
Returns
*ese?
<NR1>
where <NR1> is a decimal number from 0 to 255.
Example
*ese?
255
(command)
(response)
*esr?
Event Status Register (Query). Returns a decimal number in the range 0 to 255
corresponding to the contents of the Standard Event Status Register (SESR).
Min. Abbr.
Returns
*esr?
<NR1>
where <NR1> is a decimal number in the range 0 to 255.
Example
*esr?
213
(command)
(response)
*idn?
Identify (Query). Returns the GB1400 Generator or Analyzer identification, including
company name, BERT model number, Generator or Analyzer identifier, and software
version number.
Min. Abbr.
Returns
*idn?
TEKTRONIX, BERT-1400 [RX|TX], 0, Vs.ss
where:
RX
TX
indicates Analyzer
indicates Generator
Vs.ss = software version number (e.g. V3.00).
Example
*idn?
(command)
TEKTRONIX, BERT-1400 RX, 0, V3.00, (response)
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Remote Commands
*lrn?
Learn (Query). Returns a character string listing the instrument's current setup, except
for:
q information on the remote ports,
q calibration values,
q stored frequencies, or
q stored words
The returned string will consist of a series of commands (headers plus parameters).
These commands may be stored by the controller and used to restore the instrument to
the same setup at a later time.
Min. Abbr.
Example:
*lrn
lrn?
(command)
AUDIO_RATE 4
AUDIO_VOL 0
AUTO_SEARCH AUTO
BYTE_LENGTH 8,0
....
(response) ....
WIN_SEC_LEN "00:00:1"
WORD_ORDER MSB
*opc
Operation Complete. This command will cause the OPC bit in the Standard Event
Status Register to be set to one. If the OPC bit is enabled, this will result in an SRQ.
Thus, the *opc command can be issued after a group of setup commands to determine
when all of the setup commands have been executed.
Min. Abbr.
Example
*opc
*opc
*opc?
Operation Complete (Query). This query command will cause the instrument to return
the ASCII character for "1" when all previous commands and queries have been
completed. Thus the *opc? command may be used to determine when the instrument
has completed a group of commands.
Min. Abbr.
Example
*opc?
*opc?
1
(command)
(response) <NR1 Numeric>
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Remote Commands
*rst
Reset. This command causes the instrument to return to its factory default settings and
to enter a known operation state. Specifically *rst does the following:
q puts the instrument into the Operation Complete Command Idle State.
q puts the instrument into the Operation Complete Query Idle State.
q returns most setup parameters to their factory default settings
(Appendix B).
However *rst does not impact any of the following:
q the setup of the RS-232 or GPIB ports.
q GPIB address.
q calibration data.
q the Standard Event Status Register (SESR).
q the Event Status Enable Register (ESER).
q the power-on status clear flag setting.
q stored frequencies or words.
Min. Abbr.
Example
*rst
*rst
*sre [n]
Service Request Enable. This command sets the Service Request Enable
(SRER) to the bit sequence corresponding to n, where n is a decimal number in the range
0 to 255.
Min. Abbr.
Argument
Example
*sre
n: 0 to 255 decimal
*sre 48
(sets SRER to 00110000 binary)
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Remote Commands
*sre?
Service Request Enable (Query). This query command returns a decimal number in
the range 0 to 255 corresponding to the contents of the Service Request Enable Register,
where bit 6 is ignored.
Min. Abbr.
Returns
*sre?
<NR1>
where <NR1> is a decimal number in the range 0 to 255, where
Bit 6 is ignored.
Example
*sre?
32
(command)
(response)
(Indicates that the SRE contains 00100000 binary).
*stb?
Status Byte (Query). Returns a decimal number in the range 0 to 255 corresponding to
the contents of the Status Byte Register (SBR), where bit 6 is the Master Summary
Status bit.
Min. Abbr.
Returns
*stb?
<NR1>
where <NR1> is a decimal number in the range 0 to 255, where
Bit 6 is the Master Summary Status Bit.
Example
*stb?
96
(command)
(response)
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*tst?
Self Test. Causes the instrument to perform a self test and return the result. A result of
0 means the self test was successful. A return of any other value means the self test was
not successful. The GB1400 self test is limited in scope.
Min. Abbr.
Returns
*tst?
0
(if successful)
Example
*tst?
0
(command)
(indicates successful self test)
*wai
Wait. This command forces the instrument to stop processing any additional commands
until all pending operations are completed.
Min. Abbr.
*wai
tse [v] (Analyzer Only)
Test Status Enable. This command sets the Test Status Enable Register to the bit
sequence corresponding to v, where v is a decimal number in the range 0 to 255.
Min. Abbr.
Argument
Example
tse
n:
<NR1>, in the range 0 to 255.
tse 255
(sets the TSR to 11111111 binary)
tse? (Analyzer Only)
Test Status Enable (Register) Query. This command returns a decimal number
representing the current contents of the Test Status Enable Register (TSER).
Min. Abbr.
Returns
tse?
<NR1>, in the range 0 to 255.
Example
tse?
TSE 255
(command)
(response)
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Remote Commands
tsr? (Analyzer Only)
Test Status Register Query. This command returns a decimal number representing
the current contents of the Test Status Register (TSR).
Min. Abbr.
Returns
tsr?
<NR1>, in the range 0 to 255.
Example
tsr?
TSR 224
(command)
(response)
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Remote Commands
Commands Shared by the Generator and
Analyzer
Except where noted, the following commands are found in both the Generator and
Analyzer command sets.
Pattern and Word Commands
Use these commands to select a pattern, enable or disable pattern inversion, create and
save word patterns, and perform related pattern functions.
data_invert [on|off]
Data Inversion. Returns current status of Output Data Polarity. This command enables
or disables logical inversion of the Generator data output bit sequence or the Analyzer
input bit sequence.
Min. Abbr.
Arguments
data_inv
on:
enables data inversion, outputs inverted data
disables data inversion, outputs true data
off:
Example
data_invert off
data_invert?
Data Inversion Query. Returns a character string indicating whether Generator output
data inversion or Analyzer input data inversion is enabled (on) or disabled (off).
Min. Abbr.
Returns
data_inv?
[on|off]
Example
data_invert?
(command)
DATA_INVERT OFF
data_pattern [prbs | word | rdata]
Data Pattern. Sets the Generator pattern mode to PRBS or word, or the Analyzer
pattern mode to PRBS, word, or reference data.
Min. Abbr.
Arguments
data_p
prbs: selects the PRBS pattern mode.
word: selects the word pattern mode.
rdata: selects the reference data mode (Analyzer only).
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Remote Commands
Example
data_pattern prbs
data_pattern?
Data Pattern Query. Returns a character string indicating the current Generator or
Analyzer data pattern mode.
Min. Abbr.
Returns
data_p?
[prbs|word]
[prbs|word|rdata]
(Generator)
(Analyzer)
Example
data_pattern?
DATA_PATTERN PRBS
(command)
(response)
prbs_length [v]
PRBS Length. Selects the current PRBS pattern which becomes the current active
pattern if and only if pattern "mode" is set to PRBS (see data_pattern command). The
argument [v] may be set to 7, 15, 17, 20, or 23 corresponding to the five PRBS patterns
that can be transmitted by the Generator and Analyzed by the Analyzer.
Min. Abbr.
Arguments
prb
7
15
7:
Selects the PRBS with a length of 2 -1 bits.
15:
17:
20:
23:
Selects the PRBS with a length of 2 -1 bits.
17
Selects the PRBS with a length of 2 -1 bits.
20
Selects the PRBS with a length of 2 -1 bits.
23
Selects the PRBS with a length of 2 -1 bits.
Example
prbs_length 23
prbs_length?
n
PRBS Length Query. Returns an integer n, where 2 -1 is the length of the current prbs
pattern.
Min. Abbr.
Returns
prb
<NR1>
which may equal 7, 15, 17, 20, or 23.
Example
prbs_length?
PRBS_LENGTH 23
(command)
(response)
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Remote Commands
recall_word [m]
Recall Word. Causes the instrument to recall the word pattern saved at location "m" and
make this pattern the current word pattern and the active pattern.
Min. Abbr.
Arguments
Example
recall_w
m:
0, 1, ..., 9
recall_word 5
save_word [m]
Save Word. Causes the instrument to save the current word pattern to word memory
location "m".
Min. Abbr.
Arguments
Example
save_w
m:
0, 1, ..., 9
save_word 5
word_bits [l], [b1 | b2]
Word Bits. Returns the programmable WORD pattern. The response will contain the
pattern length and data bytes. Sets current word length to l bits, and sets the current word
pattern to the bit sequence represented by b1 and b2.
Min. Abbr.
Arguments
word_b
l:
8 or 16.
b1:
#00 to #FF
#Q000 to #Q377
(hexadecimal)
(octal)
#B00000000 to #B11111111
(binary)
b2:
same as b1. b2 is allowed only if l (length) is set to 16
Example
word_bits 16, #B10101010, #B11110000
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Remote Commands
word_bits?
Word Bits Query. The response will be in the form [n] [byte 1] [byte 2], where n is
either 8 or 16 (the current word length) and byte 1 and byte 2 are hex, octal, or binary
representations of the first and second bytes in the pattern. Note that byte 2 will be
included only if pattern length is 16.
Min. Abbr.
Returns
word_b?
<NR1>, <non-decimal numeric(s) >
Example
word_bits?
WORD BITS 16, #HAA, #HF0
(command)
(response)
indicating that the current word length is 16 bits and the current
pattern is AAF0 hex.
word_length [l]
Word Length. Sets the current word pattern length to 8 or 16 bits.
Min. Abbr.
Argument
Example
word_l
l:
8 or 16.
word_length 16
NOTE: There is no query form to the word_length command. However, you may use
the word_bits? query to read the current word length.
word_mem_len [m], [l]
Word Memory Length. Sets the length of the word pattern saved in location m to l
bits.
Min. Abbr.
Arguments
word_mem_l
m:
0, 1, ..., 9
8 or 16.
l:
Example
word_mem_len 5, 16
(sets the length of word memory 5 to 16 bits)
NOTE: There is no query form to this command. However, you can use the
word_memory? [m] query to read the length of the word saved at location m.
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Remote Commands
word_mem_ord [m], [msb | lsb]
Word Memory Order. Sets the bit order of the word saved at location m to either
"msb" (most significant bit first) or "lsb" (least significant bit first).
Min. Abbr.
Arguments
word_mem_o
m:
0, 1, ..., 9
msb: most significant bit first
lsb:
word_mem_ord 9, msb
(selects the most significant bit first order for
word memory location 9)
least significant bit first
Example
word_mem_ord?
Word Memory Order Query (All). Returns a command string ("MSB" or "LSB")
indicating the bit order of each of the 10 word memory locations.
The response will consist of 10 message units, separated by
semi-colons ";" and will contain the memory location, and word
order of each memory.
Min. Abbr.
Returns
word_mem_o?
<NR1>, [MSB|LSB]; <NR1> [MSB|LSB]; ... etc.
Example
word_mem_ord?
(command)
(response)
WORD_MEM_ORD 0, LSB;
WORD_MEM_ORD 1 MSB;
WORD_MEM_ORD 2 MSB;
....
word_mem_ord? [m]
Word Memory Order Query. Returns a command string ("MSB" or "LSB")
indicating the bit order of the word saved at location m.
Min. Abbr.
Arguments
Returns
word_mem_o
m:
0, 1, ..., 9
"MSB" or "LSB"
Example
word_mem_ord? 1
WORD_MEM_ORD 1, LSB
(command)
(response)
which indicates that the word order of word memory location 1 is
"least significant bit first".
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Remote Commands
word_memory [m], [l], [b1], [b2]
Word Memory. Stores into word memory m the word pattern of length l, with a bit
sequence represented by b1 and b2.
Min. Abbr.
Arguments
word_memo
m:
l:
decimal in range 0 to 9.
8 or 16
b1:
#00 to #FF
#Q000 to #Q377
#B00000000 to #B11111111
(hexadecimal)
(octal)
(binary)
b2:
same as b1. However, b2 is allowed only if l (length)
is set to 16.
Example
word_memory 3, 16, #HC4, #HF0
Stores the 16-bit sequence C4F0 (hex) into word memory 3.
word_memory? [m]
Word Memory Query. Returns the 8 or 16-bit pattern saved in word memory m in the
form: [m], [byte 1], [byte 2], where m is either 8 or 16 (word length in bits), and byte 1
and byte 2 are hex representations of the first and second bytes in the pattern. Note that
byte 2 will be included only if pattern length is 16. word_memory? returns the contents
of all programmable WORD memories. The response will units separated by semi-colons
and will contain the memory location, length and data bytes of each memory.
Min. Abbr.
Arguments
Returns
word_memo?
m: 0 to 9
<NR1>, <NR1>, <non-decimal numeric(s)>
Example
word_memory? 4
WORD_MEMORY 4, #H87, #H76
(command)
(response)
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Remote Commands
word_order [msb | lsb]
Word Order. Sets the bit order of the current word to MSB or LSB. The unit will start
the transmission with the MSB of the first byte or the LSB of the first byte (MSB/LSB).
After the MSB (or LSB), the bits would be transmitted continuing with the bits of the first
byte until the LSB (or MSB) is reached, then proceeding with the next byte in the same
order.
Min. Abbr.
Arguments
word_o
msb: most significant bit first
lsb:
least significant bit first.
Example
word_order lsb
Note: On changing the WORD ORDER, the new setting is effective only on pattern
bytes edited after the change. If the ORDER is changed in the middle of programming
pattern bytes, the bytes programmed prior to the ORDER change will be reversed from
those programmed after the change.
For example, if the WORD ORDER was previously LSB in memory 6, and the data
pattern is programmed as follows:
edit_begin 6
byte_length 4,0
byte_block 0,16,#HAA,#HAA
word_order MSB
byte_block 2,16,#HAA,#HAA
edit_end 6
The pattern would become #H55, #H55, #HAA, #HAA.
Example #1 - To download a 32,768-byte pattern to memory location 1 without affecting
the current 256K pattern.
edit_begin 1
word_order msb
byte_length 32768,0
byte_block 0,80,#H00,#H01,#H02,#H03,#H04,#H05,#H06,#H07,#H08,#H09
byte_block 10,80,#H00,#H01,#H02,#H03,#H04,#H05,#H06,#H07,#H08,#H09
.
.
.
byte_block 32750,80,#H00,#H01,#H02,#H03,#H04,#H05,#H06,#H07,#H08,#H09
byte_block 32760,64,#H00,#H01,#H02,#H03,#H04,#H05,#H06,#H07
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Remote Commands
edit_end 1
Example #2 - To edit memory location 6 and save into memory location 8 without
affecting the current pattern or location 6.
edit_begin 6
word_order msb
byte_block 12,16,#H24,#H23
edit_end 8
If the data pattern to be programmed is not of the same WORD ORDER as that
associated with the pattern memory location being used, the WORD ORDER must be
specified prior to any editing or downloading.
Example #3 - To select 512K word mode and have a particular stored pattern with
different current pattern.
byte_mode 512
edit_begin -1
word_order msb
byte_length 65536,0
byte_fill 48,#H00,#H22#H44,#H66,#H88,#HAA
edit_end -1
save_word 0
edit_begin -1
word_order lsb
byte_len 48600,0
byte_fill 8,#HAA
byte_block 0,72,#HF6,#HF6,#HF6,#H28,#H28,#H28,#H01,#H02,#H03
.
.
.
edit_end -1
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Remote Commands
When changing the BUFFER MODE, the stored patterns and the current pattern may be
lost. When transitioning from a smaller mode to a larger mode, some of the stored
patterns will be lost. When going from larger to smaller, those patterns (including the
current pattern) which have lengths greater than the allowed length will be initialized.
Memory allocation for Word Memory storage
1M
…………………………..
**
512K WORD0…………………………….
256k WORD0………….WORD1………..WORD2…….
128k WORD0..WORD1..WORD2..WORD3..WORD4..WORD5..
64K
0.. 1.. 2.. 3.. 4.. 5.. 6.. 7.. 8.. 9..
** The 1M storage area is used only for the current WORD pattern.
The chart above can be used to determine which stored patterns will be saved after a
MODE transition and in which storage location it will be found. For example, on
transitions from 128K to 256K, the stored patterns 0, 2 and 4 of the 128K mode will be
found at the 256K locations 0, 1, and 2 respectively, while the stored patterns at 1, 3 and 5
of the 128K will be lost.
On switching to a smaller MODE, only when the pattern in the storage area has a length
greater than the new allowed length, will be lost. (Except for 128K to 64K, where
WORD5 will always be lost).
word_order?
Word Order Query. Returns WORD transmission order. Returns a character string
(MSB or LSB) indicating the bit order of the current word.
Min. Abbr.
Response
Example
word_o?
"MSB" or "LSB"
word_order?
(command)
WORD_ORDER LSB (response)
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Remote Commands
word_memory?
Word Memory Query. Returns the all ten programmable WORD memories. The
response will be ten message units separated by semi-colons ";", and each will contain the
memory location, length and data bytes of each memory.
Response
<NR1 Numeric>
<NR2 Numeric>
<non-decimal numeric(s)>
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Remote Commands
GPIB and RS-232 Commands
gpib_address [v]
GPIB Address. This command sets the instrument's GPIB address to v. It may only be
issued via the instrument's RS-232C port.
Min. Abbr.
Arguments
Example
gpib_a
v:
0, 1, ..., 30.
gpib_address 15
gpib_address?
GPIB Address Query. This command returns a decimal number indicating the
instrument's GPIB address. It may only be issued over the RS-232C port.
Min. Abbr.
Returns
gpib_a?
<NR1>
Example
gpib_address?
GPIB_ADDRESS 15
(command)
(response)
gpib_bus [off_bus | talk_listen ]
GPIB Bus Mode. This command sets the instrument's gpib bus mode. It may be used
only over the RS-232C port.
Min. Abbr.
Arguments
gpib_b
off_bus: puts instrument in the gpib off-bus mode In this mode
it will not communicate over the GPIB.
talk_listen puts the instrument on-bus as a talker/listener.
gpib_bus talk_listen
Example
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Remote Commands
gpib_bus?
GPIB Bus Mode Query. Returns a character string indicating the current GPIB bus
mode. May be used only over the RS-232C port .
Min. Abbr.
Returns
gpib_b?
[off_bus | talk_listen]
Example
gpib_bus?
GPIB_BUS TALK_LISTEN
(command)
(response)
rs_echo [on|off]
RS-232C Echo. Enables or disables character echo on the RS-232C (serial) port.
Min. Abbr.
Arguments
rs_e
on:
Enables ECHO mode, instrument will echo back each
character received.
off:
Disables ECHO mode, instrument will not echo received
characters.
Example
rs_echo on
rs_echo?
RS-232C Echo Query. Returns a character string indicating whether RS-232C port
echo is enabled (ON) or disabled (OFF).
Min. Abbr.
Returns
rs_e?
[on|off]
Example
rs_echo?
RS_ECHO OFF
(command)
(response)
rs_pmt_lf [on|off]
RS-232C Prompt Line Feed. This command may be used to add the current RS-232C
end of line (EOL) terminator, that is CR, LF, CR+LF, or LF+CR, to the end of the
prompt. This feature may be useful when operating the instrument under program control
via a serial (RS-232) link.
Min. Abbr.
rs_pm
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Remote Commands
Arguments
Example
on:
off:
EOL terminator added to end of prompt (OAH)
no terminator added to prompt.
rs_pmt_lf on
rs_pmt_lf?
RS-232C Prompt Line Feed Query. Returns a character string indicating whether
RS-232C prompt line feed (OAH) is enabled (on) or disabled (off).
Min. Abbr.
Returns
rs_pm
[on|off]
Example
rs_pmt_lf?
RS_PMT_LF ON
rs_prompt [s]
RS-232C Prompt. This command sets the prompt on the RS-232C port to the character
string contained in the quoted string s. This string will appear at the start of each new line
on a terminal display. Maximum length is 8 characters.
Min. Abbr.
Arguments
Example
rs_pr
s:
<qstring>, a character string inside double quotes
(command)
will change the prompt to: GB1400>
rs_prompt "GB-1400 >"
þ
NOTE: This command may be issued with a null string ("") argument to disable the RS-
232C prompt.
rs_xon_xoff [on|off]
RS-232C XON/XOFF. This command enables or disables XON/XOFF flow control on
the RS-232C port.
Min. Abbr.
Arguments
rs_x
on:
off:
enables XON/XOFF flow control
disables XON/XOFF flow control
Example
rs_xon_xoff on
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Remote Commands
rs_xon_xoff?
RS-232C Xon/Xoff Query. This command returns a character string indicating whether
RS-232C port Xon/Xoff flow control is enabled or disabled.
Min. Abbr.
Returns
rs_x?
[on|off]
Example
rs_xon_xoff?
RS_XON_XOFF ON
(command)
(response)
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Remote Commands
Misc. Shared Commands
all_mem?
All Memory (Generator). Returns a character string indicating the current Generator
clock source (INT or EXT), the contents of all 10 Generator frequency memories, and the
contents of all 10 Generator word memories.
Min. Abbr.
Returns
all_?
<string>
<NR1>, <NR3>
<NR1>, <NR1>, <Non-decimal numerics>
Example
all_mem?
(command)
(response)
CLOCK_SOURCE INT;
CLOCK_MEMORY 0, 500.000E+6;
CLOCK_MEMORY 1, 550.000E+6;
...
CLOCK_MEM 9, 700.000E+6;
WORD_MEMORY 0, 16, #HAA, #HBB;
WORD_MEMORY 1, 8, #HF0;
...
WORD_MEMORY 9, 16, #HFF, #H00
All Memory (Analyzer). Returns the contents of all 10 Analyzer word memories.
Returns
Example
<NR1>, <NR1>, <Non-decimal numerics>
all_mem?
(command)
(response)
WORD_MEMORY 0, 8, #HFF;
WORD_MEMORY 1, 16, #HAA, #H00;
....
WORD_MEMORY 9, 8, #H00
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Remote Commands
header [on | off]
Header. Tells the instrument whether or not to include headers (command names) in
responses.
Min. Abbr.
he
Arguments
on:
include headers
off:
do not include headers
Example
header on
header?
Header Query. Returns a character string indicating the instrument's header status.
Min. Abbr.
Returns
he?
[on | off]
Example
header?
HEADER ON
(command)
(response)
logo?
Logo Query. Returns a character string showing the Generator or Analyzer "logo"
including company name, BERT model number, Generator or Analyzer identifier, and
software version number. This command may be used only on the RS-232C port. Use
the *idn? query to get this same information over the GPIB port.
Min. Abbr.
Returns
l?
**** TEKTRONIX BERT-1400 [RX|TX] Vs.ss mm/yy
where:
RX
TX
indicates Analyzer
indicates Generator
Vs.ss = software version number (e.g. V3.00)
mm/yy = software revision month and year.
Example
logo?
**** TEKTRONIX BERT-1400 RX V3.00 10/93
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Remote Commands
options?
Options Query. Returns a character string listing all of the options installed in the
instrument, or returns the character string NONE indicating that no options are installed.
Min. Abbr.
Returns
op?
<string> , <string> , etc. where possible strings are:
1 MB
Indicates 1 MB Option installed
Indicates PROM Option installed
Indicates 75 ohm Option installed
Indicates BURST Mode installed
Indicates PECL Mode installed.
Indicates no options are installed.
PROM
75 OHM
BURST
PECL
NONE
Examples
options?
(command)
OPTIONS NONE
(response)
options?
(command)
(response)
OPTIONS 1 MB, PROM, 75 OHM,
BURST, PECL
options?
OPTIONS 1 MB
(command)
(response)
view_angle [v]
View Angle. This command sets the LCD display viewing angle to "v".
Min. Abbr.
Arguments
Example
v
v
<NR1>, may equal 0 (lowest), 1, 2, or 3.
view_angle 2
view_angle?
View Angle Query. Returns a decimal number indicating the current LCD display view
angle setup.
Min. Abbr.
Returns
v?
<NR1>
Example
view_angle?
VIEW_ANGLE 2
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Remote Commands
Generator Commands
The following commands are found only in the Generator command set.
Clock Source and Frequency Setup Commands
clock_freq [v]
Clock Frequency. Sets the clock frequency to a value [v], specified in Hz, over the
range of 1 MHz to 1405 MHz in steps of 1kHz.
Min. Abbr.
Arguments
clock_f
v
<NR3>, in the range 1.000E+6 to 1405.000E+6 in steps
of 0.001E+6.
Example
clock_freq 622.000E+6.
clock_freq?
Clock Frequency Query. Returns the current Generator clock frequency setting.
Min. Abbr.
Returns
clock_f
<NR3>
Example
clock_freq?
CLOCK_FREQ 0.150E+6
(command)
(response)
clock_memory?
Clock Memory Query. Returns the contents of all ten frequency memory locations.
The response will be 10 message units separated by semi-colons ";", and will contain the
memory location and frequency.
Returns
<NR1 Numeric>
<NR3 Numeric>
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Remote Commands
clock_memory [m], [f]
Clock Memory. Sets the frequency saved at frequency memory location [m] to a
specified value [f], in the range 1 MHz to 1405 MHz, in steps of 1 kHz.
Min. Abbr.
Arguments
clock_m
m:
f:
<NR1>, in the range 0, 1, ..., 9
<NR3>, in the range 1.000E+6 to 1405.000E+6 in steps
of 0.001E+6
Example
clock_memory 9, 100.000E+6
clock_memory? [m]
Clock Memory Query. Returns the frequency saved at frequency memory location
[m]. The response will contain the memory location and the frequency.
Min. Abbr.
Returns
clock_m?
m <NR1>, <NR3>, in the range 0-9
Example
clock_memory? 4
CLOCK_MEMORY 4, 100.000E+6
(command)
(response)
clock_source [int|ext]
Clock Source. Sets the clock mode of the Generator to either internal (int) or external
(ext).
Min. Abbr.
Arguments
clock_so
int
Selects the internal clock source
Selects the external clock source.
ext
Example
clock_source int
clock_source?
Clock Source Query. Returns a character string indicating the current Generator clock
mode.
Min. Abbr.
Returns
clock_so?
[int|ext]
Example
clock_source?
CLOCK_SOURCE INT
(command)
(response)
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Remote Commands
clock_step [v]
Clock Step. Sets the clock frequency increment/decrement default step size 10 kHz,
100 kHz, 1 MHz, 10 MHz, 100 MHz, or 1000 MHz.
Min. Abbr.
Arguments
clock_ste
v: <NR3>, in the range: 0.010E+6, 0.100E+6,
1.000E+6, 10.000E+6, 100.000E+6 or 1000.000E+6
clock_step 1.000E+6
Example
clock_step?
Clock Step Query. Returns the current clock frequency step size.
Min. Abbr.
Returns
clock_ste?
<NR3>
Example
clock_step?
CLOCK_STEP 1.000E+6
(command)
(response)
clock_stp_up and clock_stp_dn
Clock Step Up, Clock Step Down. This command pair is used to increment or
decrement the current Generator frequency using the step size previously defined with the
clock_step command.
Min. Abbr.
clock_stp_u
clock_stp_d
Arguments
Example
none
clock_step_up
clock_step_dn
clock_stp_up [v] and clock_stp_dn [v]
Clock Step Up, Clock Step Down. This command pair is used to increment or
decrement the current clock frequency by v, which can range from: 0.1 MHz to 1405
MHz, in 0.01 MHz steps.
Min. Abbr.
clock_stp_u
clock_stp_d
Arguments
Example
v:
<NR3>, in the range 0.100E+6 to 1405.000E+6.
clock_step_up 0.100E+6
clock_step_dn 0.100E+6
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Remote Commands
recall_freq [m]
Recall Frequency. This command recalls a previously saved frequency from memory
location [m]. The recalled frequency becomes the current frequency of the Generator
internal clock.
Min. Abbr.
Arguments
Example
recall_f
m:
<NR1>, in the range 0, 1, ..., 9.
recall_freq 5
save_freq [m]
Save Frequency. This command saves the current Generator internal clock frequency
to memory location [m],
Min. Abbr.
Arguments
Example
save_f
m:
<NR1>, in the range 0, 1, ..., 9.
save_freq 8
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Remote Commands
Output (Clock and Data) Setup Commands
amplitude [v]
Amplitude. This command sets both Data and Clock amplitudes to the same voltage [v].
Min. Abbr.
Arguments
Example
am
v:
<NR2>, in the range 0.50 to 2.00 in steps of 0.05.
amplitude 1.50
amplitude?
Amplitude Query.
Returns two message units, the first indicating the clock
amplitude setting and the second indicating the data amplitude setting.
Min. Abbr.
Returns
am?
<NR2>, <NR2>
Example
amplitude?
(command)
CLOCK_AMPL 1.450; DATA_AMPL 1.450 (response)
clock_amp_up and
clock_amp_dn
Clock Amplitude Up/Down (Default). This command pair is used to increment or
decrement the current clock amplitude setting by the default increment of 0.05 volts.
Min. Abbr.
clock_amp_u
clock_amp_d
Arguments
Example
none
clock_amp_up
clock_amp_dn
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Remote Commands
clock_amp_up [v] and
clock_amp_dn [v]
Clock Amplitude Up/Down. This command pair is used to increment or decrement the
current clock amplitude by specified amount of [v] volts.
Min. Abbr.
clock_amp_u
clock_amp_d
Arguments
Example
v:
<NR2>, in range 0.05 to 1.50 in steps of 0.05.
clock_amp_up 0.05
clock_amp_dn 0.05.
clock_ampl [v]
Clock Amplitude. This command sets the output clock amplitude to [v] volts.
Min. Abbr.
Arguments
Example
clock_ampl
v
<NR2>, in the range 0.50 to 2.00 in steps of 0.05
clock_amplitude 2.00
clock_ampl?
Clock Amplitude Query. Returns the current output clock amplitude setting.
Min. Abbr.
Response:
Example:
clock_ampl?
<NR2>
clock_ampl?
(command)
CLOCK_AMPL 1.40
clock_off_up and
clock_off_dn
Clock Offset Up, Clock Offset Down (Default). This command pair is used to
increment or decrement the current output clock signal baseline offset by a default value
of 0.05 volts.
Min. Abbr.
clock_off_u
clock_off_d
Arguments
none
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Remote Commands
Examples
clock_off_up
clock_off_dn
clock_off_up [v] and
clock_off_dn [v]
Clock Offset Up, Clock Offset Down. This command pair is used to increment or
decrement the current output clock signal baseline offset by a specified amount [v] volts.
Min. Abbr.
clock_off_u
clock_off_d
Arguments
v: <NR2>, in the range 0.05 to 3.00 in 0.05 v steps.
in the range 0.05 to 3.80 in 0.05 v steps (PECL option)
Example
clock_off_up 0.10
clock_off_dn 0.10
clock_offset [v]
Clock Offset. Sets the baseline offset of the output clock signal to [v] volts.
Min. Abbr.
Arguments
clock_offs
v: <NR2>, in the range -2.00 to 1.00 in steps of 0.05.
in the range -2.00 to 1.80 in 0.05 v steps (PECL option)
clock_offset -0.75
Example
clock_offset?
Clock Offset Query. Returns the current value of the output clock signal baseline
offset.
Min. Abbr.
Returns
clock_offs?
<NR2>
Example
clock_offset?
CLOCK_OFFSET -0.75
(command)
(response)
data_amp_up and
data_amp_dn
Data Amplitude Up/Down (Default). This command pair is used to increment or
decrement the current amplitude of the Generator data output by a default amount of 0.05
volts.
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Remote Commands
Min. Abbr.
data_amp_u
data_amp_d
Arguments
Example
none
data_amp_dn
data_amp_up [v] and
data_amp_dn [v]
Data Amplitude Up, Data Amplitude Down. This command pair is used to increment
or decrement the current amplitude of the Generator data output by a specified step size
of [v] volts.
Min. Abbr.
data_amp_u
data_amp_d
Arguments
Example
v:
<NR2>, in the range 0.05 to 1.50, in steps of 0.05.
data_amp_up 1.00
data_ampl [v]
Data Amplitude. Sets the amplitude of the Generator's data output signal to [v] volts.
Min. Abbr.
Arguments
Example
data_ampl
v:
<NR2>, in the range 0.50 to 2.00 in steps of 0.05.
data_ampl 1.00
data_ampl?
Data Amplitude Query. Returns the current amplitude setup of the Generator's data
output signal.
Min. Abbr.
Returns
data_ampl?
<NR2>
Example
data_ampl?
DATA_AMPL 1.00
(command)
(response)
data_off_up and
data_off_dn
Data Offset Up/Down (Default). This command pair is used to increment or decrement
the current baseline offset of the Generator data output by a default amount of 0.05 volts.
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Remote Commands
Min. Abbr.
data_off_u
data_off_d
Arguments
Example
none
data_off_up
data_off_up [v] and
data_off_dn [v]
Data Offset Up, Data Offset Down. This command pair is used to increment or
decrement the current baseline offset of the Generator data output by a specified step size
of [v] volts.
Min. Abbr.
data_off_u
data_off_d
Arguments
v: <NR2>, in the range 0.05 to 3.00, in steps of 0.05.
in the range 0.05 to 3.80 in 0.05 v steps (PECL option)
data_off_up 0.20
Example
data_offset [v]
Data Offset. Sets the baseline offset of the Generator data output to a specified value of
[v] volts.
Min. Abbr.
Arguments
data_offs
v: <NR2>, in the range -2.00 to 1.00 in steps of 0.05.
in the range -2.00 to 1.80 in 0.05 v steps (PECL option)
data_offset -0.50
Example
data_offset?
Data Offset Query. Returns the current baseline offset of the Generator data output in
terms of volts.
Min. Abbr.
Returns
data_offs?
<NR2>
Example
data_offset?
DATA_OFFSET -0.50
(command)
(response)
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Remote Commands
offset [v]
Offset. This command sets the Generator clock and data baseline offset to the same
specified value of [v] volts.
Min. Abbr.
Arguments
off
v: <NR2>, in the range -2.00 to 1.00 in steps of 0.05.
in the range -2.00 to 1.80 in 0.05 v steps (PECL option)
offset 1.50
Example
offset?
Offset Query. Returns two message units, the first containing the Generator clock
output baseline offset and the second containing the Generator data output baseline
offset.
Min. Abbr.
Returns
off
<NR2>, <NR2>
Example
offset?
CLOCK_OFFSET 1.500
DATA_OFFSET 1.500
(command)
(response)
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Remote Commands
Error Injection Commands
error_rate [off|ext|rate_3|rate_4|rate_5|rate_6|rate_7]
Error Rate. Sets the Generator output bit error injection rate to "off", "external", or one
-3 -4 -5 -6
-7
of the following specified values: 10 , 10 , 10 , 10 , or 10 .
Min. Abbr.
Arguments
error_r
off:
turns error injection off.
ext:
selects the external error injection mode.
-3
rate_3
rate_4
rate_5
rate_6
rate_7
sets bit error injection rate to 10 .
-4
sets bit error injection rate to 10 .
-5
sets bit error injection rate to 10 .
-6
sets bit error injection rate to 10 .
-7
sets bit error injection rate to 10 .
Example
error_rate rate_6
error_rate?
Error Rate Query. Returns a character string indicating the current Generator output
error injection mode and rate.
Min. Abbr.
Returns
error_r?
[off|ext|rate_3|rate_4|rate_5|rate_6|rate_7]
Example
error_rate?
ERROR_RATE RATE_6
(command)
(response)
error_single
Error Single. This command injects a single bit error into the Generator output signal.
Min. Abbr.
Arguments
Example
error_s
none
error_single
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Remote Commands
Analyzer Commands
The following commands are found only in the Analyzer command set.
Results Retrieve Commands
Analyzer results commands are used to query the Analyzer for Test, Window, and
Totalize interval results. Note that Analyzer numeric results are returned in one three
basic formats:.
q <NR1> or integer results, which include various counts such as bits or bit errors,
up to a maximum of 16 digits. Examples: 0, 1, 15, 45959, 1234567890123456.
Note that at a bit rate of 700 Mb/s, 16 digits can represent a bit count equivalent
to over 165 days.
q <NR2> or "real number without exponent" results, such as percentages.
Examples: 100.00. 99.99, 0.01, 0.00, 50.00, 27.83.
q <NR3> or "real numbers with exponent" results, such as BER, have three
significant digits, with two places to the right of the decimal place, and a signed
exponent following the letter "E". Examples: 1.00E-9, 9.99E-7, 2.08E-14.
þ
NOTE: Returning Current or Previous Test Results. In response to queries for test
interval results, the Analyzer will return results from the current interval (so far), or from
the previous interval, based on the following rules:
1. If the TEST PREV has been set to CURRENT and a test is in progress, then the
instrument will return results from the current test interval. A test is in progress
after TEST STATE is set to RUN, until the controller (or user) sets TEST
STATE to STOP, or the instrument automatically stops a test at the end of a
timed test interval.
2. If TEST PREV has been set to PREVIOUS and there are previous results
available, then the instrument will return results from the previous test interval.
Previous results become available after TEST STATE has made at least one
RUN to STOP transition.
3. Otherwise, the Analyzer will not return results but instead will set the EXE bit (bit
4) of the Standard Event Status Register (SESR).
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Remote Commands
clock_freq?
Clock Frequency. Returns the CLOCK input frequency in Hz that is measured by the
Analyzer.
Min. Abbr.
clock_f
Returns
Example
<NR3>, in format ddd.ddE+6
clock_freq?
CLOCK_FREQ 700.00E+6
(command)
(response)
res_bits?
Results Bits Query. This command returns the number of bits counted, either in the
current interval so far or the previous test interval, depending on the setup of TEST
PREV and the current test state.
Min. Abbr.
Returns
res_b?
<NR1>
Example
res_bits
RES BITS 4230452921
(command)
(response)
res_cur_rate?
Results Current Rate Query. This command returns the BER measured, either in the
most recent second of the current test interval or the last second of the previous test
interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_c?
<NR3>
Example
res_cur_rate?
RES_CUR_RATE 1.00E-6
(command)
(response)
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Remote Commands
res_dm?
Results Degraded Minutes Query. This command returns the number of degraded
minutes counted, either in the current interval so far or in the previous test interval,
depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_dm?
<NR1>
Example
res_dm?
RES_DM 12
(command)
(response)
res_dm_per?
Results Degraded Minutes Query. This command returns the percentage of
degraded minutes calculated, either in the current test interval so far or in the previous test
interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_dm_?
<NR2>
Example
res_dm_per?
RES_DM_PER 20.20
(command)
(response)
res_efs?
Results Error-Free Seconds. This command returns the number of error free seconds
counted, either in the current test interval so far or in the previous test interval, depending
on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_efs?
<NR1>
Example
res_efs?
RES_EFS 273
(command)
(response)
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Remote Commands
res_efs_per?
Results Error-Free Seconds. This command returns the percentage of error free
seconds calculated, either in the current test interval so far or in the previous test interval,
depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_efs_?
<NR2>
Example
res_efs_per?
RES_EFS_PER 100.00
(command)
(response)
res_elapsed?
Results Elapsed (Time). This command returns a quoted string indicating the time
elapsed, either in the current interval so far or the previous interval, depending on the
setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_el?
<qstring>, in format "ddd-hh:mm:ss", where ddd = days, hh =
hours, mm = minutes, and ss = seconds.
Example
res_elapsed?
(command)
RES_ELAPSED "000-23:52:30"(response)
res_errors?
Results Errors. This command returns the total number of bit errors counted, either in
the current test interval so far or in the previous test interval, depending on the setup of
TEST PREV and the current test state.
Min. Abbr.
Returns
res_er?
<NR1>
Example
res_errors?
RES_ERRORS 81252873
(command)
(response)
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Remote Commands
res_es?
Results Errored Seconds. This command returns the total number of errored seconds
counted, either in the current test interval so far or in the previous test interval, depending
on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_es?
<NR1>
Example
res_es?
RES_ES 384
(command)
(response)
res_es_per?
Results Error-Free Seconds Percentage. This command returns the percentage of
errored seconds calculated, either in the current test interval so far or in the previous test
interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_es_?
<NR2>
Example
res_es_per?
RES_ES_PER 89.35
(command)
(response)
res_los?
Results Loss of Signal Seconds. This command returns the total number of seconds
counted, that contained a loss of signal event, either in the current test interval so far or in
the previous test interval, depending on the setup of TEST PREV and the current test
state.
Min. Abbr.
Returns
res_l?
<NR1>
Example
res_los?
RES_LOS 1
(command)
(response)
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Remote Commands
res_pha_es?
Results Phase Errored Seconds. This command returns the total number of phase
errored seconds counted, either in the current test interval so far or in the previous test
interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr. res_p?
Returns
Example
<NR1>
res_pha_es?
RES_PHA_ES 591
(command)
(response)
res_ses?
Results Severely Errored Seconds. This command returns the total number of
severely errored seconds counted, either in the current test interval so far or in the
previous test interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_ses?
<NR1>
Example
res_ses?
RES_SES 1290121
(command)
(response)
res_ses_per?
Results Severely Errored Seconds Percentage. This command returns the
percentage of severely errored seconds counted, either in the current test interval so far
or in the previous test interval, depending on the setup of TEST PREV and the current
test state.
Min. Abbr.
Returns
res_ses_?
<NR2>
Example
res_ses_per?
RES_SES_PER 27.70
(command)
(response)
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Remote Commands
res_start?
Results Start (Time). This command returns a quoted string indicating the start time,
either of the current test interval or the previous test interval, depending on the setup of
TEST PREV and the current test state.
Min. Abbr.
Returns
res_sta?
<qstring>, <qstring> in the format: yy/mm/dd
"hh:mm:ss.th" where yy = year, mmm = month (JAN, FEB, ...,
DEC), dd = day, hh = hours, mm = minutes, ss = seconds, th =
tenths and hundreds of seconds.
Example
res_start?
(command)
(response)
RES_START "20/DEC/93, "14:00:00.00"
res_stop?
Results Stop (Time). Returns a quoted string indicating the stop time of the previous
test interval. This command will produce a return if and only if previous results are
available. Previous results become available after TEST STATE has made at least one
RUN to STOP transition.
Min. Abbr.
Returns
res_sto?
<qstring>, <qstring> in the format: yy/mm/dd
"hh:mm:ss.th" where yy = year, mmm = month (JAN, FEB, ...,
DEC), dd = day, hh = hours, mm = minutes, ss = seconds, th =
tenths and hundreds of seconds.
Example
res_stop?
(command)
RES_STOP "20/DEC/93", "14:30:00.00" (response)
res_sync?
Results Synchronization Loss Seconds. This command returns the number of
seconds in which one or more pattern synchronization loss events occurred, either in the
current test interval so far or in the previous test interval, depending on the setup of TEST
PREV and the current test state.
Min. Abbr.
Returns
res_sy?
<NR1>
Example
res_sync?
RES_SYNC 23
(command)
(response)
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Remote Commands
res_tes?
Results Threshold Errored Seconds. This command returns the total number of
threshold errored seconds counted, either in the current test interval so far or in the
previous test interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_tes?
<NR1>
Example
res_tes?
RES_TES 9823
(command)
(response)
res_tes_per?
Results Threshold Errored Seconds Percentage. This command returns the
percentage of threshold errored seconds, either in the current test interval so far or in the
previous test interval, depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_tes_?
<NR2>
Example
res_tes_per?
RES_TES_PER 5.52
(command)
(response)
res_tot_rate?
Results Total (Bit Error) Rate. This command returns the totalized error rate of the
entire current test interval so far or of the entire previous test interval, depending on the
setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_to?
<NR3>
Example
res_tot_rate?
RES_TOT_RATE 4.29E-7
(command)
(response)
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Remote Commands
res_us?
Results Unavailable Seconds. This command returns the total number of unavailable
seconds counted, either in the current test interval so far or in the previous test interval,
depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_us?
<NR1>
Example
res_us?
RES_US 120
(command)
(response)
res_us_per?
Results Unavailable Seconds Percentage. This command returns the percentage of
unavailable seconds, either in the current test interval so far or in the previous test interval,
depending on the setup of TEST PREV and the current test state.
Min. Abbr.
Returns
res_us_?
<NR2>
Example
res_us_per?
RES_US_PER 29.01
(command)
(response)
total_bits?
Totalize Bits Query. Returns the total number of bits accumulated in the current
Totalize measurement interval. The Totalize bit count is zeroed at the start of each new
Totalize measurement interval, that is at power-up and after each error reset.
Min. Abbr.
Returns
total_b?
<NR1>
Example
total_bits?
TOTAL_BITS 32365018072
(command)
(response)
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Remote Commands
total_error?
Totalize Error Query. Returns the number of bit errors counted so far in the current
Totalize measurement interval. The Totalize error count is zeroed at the start of each
new Totalize measurement interval, that is at power-up and after a error reset.
Min. Abbr.
Returns
total_e?
<NR1>
Example
total_error?
TOTAL_ERROR 20984
(command)
(response)
total_rate?
Totalize (Bit Error) Rate Query. Returns the bit error rate (BER) calculated so far in
the current Totalize measurement interval. Totalize BER equals the Totalize bit error
count divided by the Totalize bit count. The number will reset at power-up and on error
reset.
Min. Abbr.
Returns
total_r?
<NR3>
Example
total_rate?
TOTAL_RATE 8.62E-6
(command)
(response)
total_time?
Totalize Time Query. Returns a quoted string indicating the amount of time
accumulated in the current Totalize measurement interval. Totalize time is zeroed at the
start of each new Totalize measurement interval, that is at power-up and after each error
reset.
Min. Abbr.
Returns
total_t?
<qstring>, in the format "ddd-hh:mm:ss" where ddd = days,
hh = hours (00 ... 23), mm = minutes (00 ... 59), ss = seconds (00
... 59)
Example
total_time?
"000-12:34:56"
(command)
(response)
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Remote Commands
Input Setup Commands
clock_term [neg_2v | gnd | ac]
Clock Termination. Sets the Analyzer clock input termination voltage to "v".
Min. Abbr.
Arguments
clock_ter
neg_2v
gnd
50 ohms to -2 volts.
50 ohms to ground.
ac
Example
50 ohms via 0.01 mF capacitor to ground.
clock_term gnd
clock_term?
Clock Termination Query. Returns a character string indicating the current Analyzer
clock input termination setup voltage.
Min. Abbr.
Returns
clock_ter?
[neg_2v | gnd | ac ]
Example
clock_term?
CLOCK_TERM GND
(command)
(response)
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Remote Commands
data_del_up and
data_del_dn
Data Delay Up/Down (Default). This command pair is used to increment (data_del_up)
or decrement (data_del_dn) the current DATA input delay by the default amount, 0.005
nSec.
Min. Abbr.
data_del_u
data_del_d
Argument
Example
none
data_del_up
data_del_dn
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Remote Commands
data_del_up [v] and
data_del_dn [v]
Data Delay Up/Down. This command pair is used to increment (data_del_up) or
decrement (data_del_dn) the current DATA input delay by v seconds. Note that v is
expressed as a real number with an exponent and is in the range of 0.1 to 3.99 nSec in
0.005 nSec steps.
Min. Abbr.
data_del_u
data_del_d
Argument
Example
v
<NR3>, 0.1E-9 to 3.99E-9 in 0.005E-9 steps
data_del_up 0.02E-9
data_del_dn 0.10E-9
data_delay [v]
Data Delay. Sets the Analyzer DATA input delay to any value from 0.0 nS to 3.99 nS in
0.005 nSec steps. . Note that v is expressed as a real number with an exponent of -9.
Min. Abbr.
Argument
Example
data_dela
v:
0.00E-9 to 3.99E-9 in 0.005E-9 steps
data_delay 1.62E-9
data_delay?
Data Delay Query. Returns the current value of the Analyzer DATA input delay setup
parameter.
Min. Abbr.
Returns
data_dela?
<NR3>
Example
data_delay?
DATA_DELAY 1.62E-9
(command)
(response)
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Remote Commands
data_term [neg_2v | gnd | ac]
Data Termination. Sets the Analyzer data input termination voltage to "v".
Min. Abbr.
Arguments
data_te
neg_2v:
gnd
50 ohms to -2 volts.
50 ohms to ground.
ac
Example
50 ohms via 0.01 mF capacitor to ground.
data_term ac
data_term?
Data Termination Query. Returns a character string indicating the current Analyzer
data input termination setup.
Min. Abbr.
Returns
data_te?
[neg_2v | gnd | ac ]
Example
data_term?
DATA_TERM AC
(command)
(response)
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Remote Commands
data_thr_up and
data_thr_dn
Data Threshold Up/Down (Default). This pair of commands increments (data_thr_up)
or decrements (data_thr_dn) the current Analyzer DATA input threshold by the default
increment of 0.05 volts.
Min. Abbr.
data_thr_u
data_thr_d
Arguments
Examples
none
data_thr_up
data_thr_dn
(increments threshold by 0.05 volts)
(decrements threshold by 0.05 volts)
data_thr_up [v] and
data_thr_dn [v]
Data Threshold Up/Down. This pair of commands increments (data_thr_up) or
decrements (data_thr_dn) the current Analyzer DATA input threshold by an amount v.
Min. Abbr.
data_thr_u
data_thr_d
Arguments
Examples
v:
0.05 to 2.50 in 0.05 V steps
data_thr_up 0.10
data_thr_dn 2.00
(increments threshold by 0.1 volt)
(decrements threshold by 2 volts)
data_thres [v]
Data Threshold. Sets the threshold voltage for the Analyzer DATA input to v, where
the allowed range for v depends on the current DATA input termination.
Min. Abbr.
Arguments
data_thre
v: -1.50 to 1.00 in 0.05 v steps, for input terminations
GND, AC
-2.50 to 0.00 in 0.05 v steps, for input terminations -2V
Example
data_thres -1.50
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Remote Commands
data_thres?
Data Threshold Query. Returns the current threshold voltage for the Analyzer DATA
input.
Min. Abbr.
data_thre?
<NR2>
Returns
Example
data_thres?
(command)
(response)
DATA_THRES -1.50
rdata_del_up and
rdata_del_dn
Reference Data Delay Up/Down (Default). This command pair is used to increment
(rdata_del_up) or decrement (rdata_del_dn) the current REF DATA delay by the default
increment of 0.1 nSec.
Min. Abbr.
rdata_del_u
rdata_del_d
Arguments
Examples
none
rdata_del_up
rdata_del_dn
rdata_del_up [v] and
rdata_del_dn [v]
Reference Data Delay Up/Down. This command pair is used to increment
(rdata_del_up) or decrement (rdata_del_dn) the current REF DATA delay by v, where v
is in <NR3> format and may be set in the range 0.1 nSec to 3.99 nSec in 0.1 nSec steps.
Min. Abbr.
rdata_del_u
rdata_del_d
Argument
Examples
v:
<NR3>, 0.10E-9 to 3.90E-9 in 0.10E-9 steps.
rdata_del_up 1.00E-9
rdata_del_dn 1.00E-9
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Remote Commands
rdata_delay [v]
Reference Data Delay. Sets the Analyzer REF DATA input delay to v, where v may
be set in the range 0.0 nSec to 3.99 nSec in 0.1 or 0.2 nSec steps. v is expressed as a
real number with an exponent of -9.
Min. Abbr.
Argument
Example
rdata_dela
v:
0.00E-9 to 3.99E-9, in steps of 0.10E-9 or 0.2E-9
rdata_delay 1.10E-9
rdata_delay?
Reference Data Delay Query. Returns the current Analyzer REF DATA input delay.
Min. Abbr.
Returns
rdata_dela?
<NR3>
Example
rdata_delay?
RDATA_DELAY 1.10E-9
(command)
(response)
rdata_term [neg_2v | gnd | ac]
Reference Data Termination. Sets the Analyzer REF DATA input termination.
Min. Abbr.
Arguments
rdata_te
neg_2v:
gnd
50 ohms to -2 volts.
50 ohms to ground.
ac
Example
50 ohms via 0.01 mF capacitor to ground.
rdata_term neg_2v
rdata_term?
Reference Data Termination Query. Returns a character string indicating the current
Analyzer Reference Data Input termination setup.
Min. Abbr.
Returns
rdata_te?
[neg_2v | gnd | ac]
Example
rdata_term?
RDATA_TERM NEG_2V
(command)
(response)
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Remote Commands
rdata_thr_up and
rdata_thr_dn
Reference Data Threshold Up/Down (Default). This command pair is used to
increment (rdata_thr_up) or decrement (rdata_thr_dn) the current REF DATA threshold
by the default increment of 0.05 volts.
Min. Abbr.
rdata_thr_u
rdata_thr_d
Argument
Examples
none
rdata_thr_up
rdata_thr_dn
rdata_thr_up [v] and
rdata_thr_dn [v]
Reference Data Threshold Up/Down. This command pair is used to increment
(rdata_thr_up) or decrement (rdata_thr_dn) the current REF DATA threshold by v,
where v is in <NR2> format and may be set in the range 0.05 to 2.50 Volts in 0.05 V
steps.
Min. Abbr.
rdata_thr_u
rdata_thr_d
Argument
Examples
v:
<NR2>, 0.05 to 2.50 volts, in 0.05 V steps.
rdata_thr_up 0.10
rdata_thr_dn 0.50
rdata_thres [v]
Reference Data Threshold. Sets the threshold voltage for the Analyzer REF DATA
input to v, where the allowed range for v depends on the current input clock termination.
Min. Abbr.
Arguments
rdata_thre
v: -1.50 to 1.00 in 0.05 v steps, for terminations
GND, AC
-2.50 to 0.00 in 0.05 v steps, for termination -2V
Example
rdata_thres 1.00
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Remote Commands
rdata_thres?
Reference Data Threshold Query. Returns the current threshold voltage for the
Analyzer REF DATA input.
Min. Abbr.
Returns
rdata_thre
<NR2>
Example
rdata_thres?
RDATA_THRES 1.00
(command)
(response)
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Remote Commands
Error Detector and History Setup Commands
auto_search [auto | off | disab]
Auto_Search. Enables or disables the Auto Search and Automatic pattern re-alignment
functions.
Min. Abbr.
Arguments
auto_s
auto: Auto Search on, pattern re-alignment enabled
off:
Auto Search off, pattern re-alignment enabled
disab :Auto Search off, pattern re-alignment disabled
Example
auto_search auto
auto_search?
Auto_Search Query. Returns a character string representing the current setup of
AUTO SEARCH and automatic pattern re-alignment.
Min. Abbr.
Returns
auto_s?
[auto | off | disable]
Example
auto_search?
AUTO_SEARCH AUTO
(command)
(response)
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Remote Commands
auto_mode [ber, fast]
Auto_Mode. Sets the Auto Search mode for finding the Data Delay.
Arguments ber:
fast
Uses the Bit Error Rate to find the Data Eye Crossing
Uses the Clock to Data Phase to quickly find the Data Crossing
auto_mode ber
Example
auto_mode?
Returns the Auto Search Data Delay mode.
Response BER or FAST
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Remote Commands
auto_sample [n]
Auto_Sample. Sets the number of Data Bits to Sample when Auto Search is in BER
mode. This is the exponent for the number of Bits accumulated at the Delay Settings, in
terms of 10E+n:
Arguments
Example
n:
4 to 11
auto_sample 4
auto_sample?
Returns the exponent of the number of Data Delay Sampling Bits.
Response <NR1 Numeric>
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Remote Commands
auto_thresh [n]
Auto_Thresh. Sets the Error Rate Threshold used when Auto Search is in BER mode.
This the exponent for the error rate used for the Delay settings, in terms of 10E-n
Arguments
Example
n:
3 to 10
auto_thresh 3
auto_thresh?
Returns the exponent of the number used as the Data Delay Error Rate Threshold.
Response
<NR1 Numeric>
auto_width?
Returns the Width of the Data Eye as determined by Auto Search, in either mode. These
values are in terms of seconds. (Example, 100E-12 is 100 pS.) The following delay error
codes are returned if appropriate:
1
Only 1 Data Eye Crossing found
No Data Eye Crossing found
Auto Search not run
2
3
Response
<NR1 Numeric>
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Remote Commands
disp_select [total | window | test]
Display Select. Selects the total, window, or test display mode. The display mode
determines which BER and bit error results are shown in the top-middle, and top-right
fields respectively of the display.
Min. Abbr.
Arguments
dis
total: selects the Totalize display mode, Totalize Error
Rate/Total
window: selects the Window display mode, Window Error Rate/
Total
test: selects the Test display mode, Test Error Rate/Total
Example
disp_select test
disp_select?
Display Select Query. Returns a character string that indicates the current display
mode of the Analyzer.
Min. Abbr.
Returns
dis?
[total | window | test]
Example
disp_select?
DISP_SELECT TEST
(command)
(response)
error_reset
Error Reset. This command resets the Totalize and Window measurement processes.
This does not affect Test results.
Min. Abbr.
Arguments
Example
er
none
error_reset
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Remote Commands
histry_bits?
History Bits Query. Returns a character string indicating the state of the BIT error
history indicator.
Min. Abbr.
Returns
histry_b?
[on | off]
Example
histry_bits?
HISTRY_BITS OFF
(command)
(response)
histry_clear
History Clear. This command clears (resets) all four Analyzer history LEDs: Sync
Loss, Bit Error, Phase Error, and Power Loss.
Min. Abbr.
Arguments
Example
histry_c
none
histry_clear
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Remote Commands
histry_phase?
History Phase. Returns a character string indicating the state of the PHASE error
history indicator.
Min. Abbr.
Returns
histry_ph?
[on | off]
Example
histry_phase?
HISTRY_PHASE ON
(command)
(response)
histry_power?
History Power. Returns a character string indicating the state of the POWER Loss
history indicator.
Min. Abbr.
Returns
histry_po?
[on | off]
Example
histry_power?
HISTORY_POWER OFF
(command)
(response)
histry_stat?
History Status Query. This command returns a summary of the Analyzer's front panel
status. The response will be in the form of multiple message units separated by
semicolons.
Min. Abbr.
Returns
histry_st?
Window error rate
Totalize error rate
Received clock frequency
Sync Lock status
History status indicators
<NR3>
<NR3>
<NR3>
[on | off]
[on | off]
Example
histry_stat
(command)
(response)
WIN_RATE 1.5E-03;
TOTAL_RATE 3.7E-06;
CLOCK_FREQ 701.47E+6;
SYNC OFF;
HISTRY_SYNC ON;
HISTRY_BITS ON;
HISTRY_PHASE OFF;
HISTRY_POWER OFF
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Remote Commands
histry_sync?
History Sync Indicator Query. Returns a character string indicating the state of the
SYNC Loss history indicator.
Min. Abbr.
Returns
histry_sy?
[on | off]
Example
histry_sync?
HISTRY_SYNC OFF
(command)
(response)
sync?
Synchronization Query. Returns a character string indicating whether the Analyzer
synchronization LOCK LED is on or off. If it is on, then the Analyzer is in pattern
synchronization. If it is off, then the Analyzer is out of pattern synchronization.
Min. Abbr.
Returns
sy?
[on|off]
Example
sync?
SYNC ON
(command)
(response)
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Remote Commands
TEST Setup Commands
test_discard
Test Discard. This command discards all results from the previous test interval, making
previous results unavailable until the next test state RUN to STOP transition occurs.
Min. Abbr.
Arguments
Example
test_d
none
test_discard
test_length [t]
Test Length. Sets the test length to the time specified in the string "s". The string will be
in 24-hour format "HH:MM:SS" enclosed in single or double quotes. This command sets
the timed test interval. This interval will be in effect only when the test mode is timed or
repeat.
Min. Abbr.
Arguments
test_l
t <qstring>, in format "hh:mm:ss", where hh = hours
(0 to 24) mm = minutes (0 to 59), ss = seconds (0 to 59).
Example
test_length "02:00:00"
test_length?
Test Length Query. Returns the current value of the timed test length parameter.
Min. Abbr.
Returns
test_l?
<qstring>, in format "hh:mm:ss"
Example
test_length?
TEST_LENGTH "02:00:00"
(command)
(response)
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Remote Commands
test_mode [untimed|timed|repeat]
Test Mode. Sets the test timing mode. The test once started, will stop and start
according to the mode.
Min. Abbr.
Arguments
test_m
untimed: after test start, a test interval will continue until a test
stop command is received, or the test is stopped manually from
the front panel, or power loss.
timed: after a test start, a test interval will stop automatically
after test length has elapsed, front panel key, remote command or
power loss.
repeat: after test start, a test interval will stop and then restart
automatically after test length has elapsed. This process will
continue until a test stop command is received, or testing is
stopped manually from the front panel, or by power loss.
Example
test_mode timed
test_mode?
Test Mode Query. Returns the current Analyzer test timing mode.
Min. Abbr.
Returns
test_m?
[untimed|timed|repeat]
Example
test_mode?
TEST_MODE TIMED
test_prev [current|previous]
Test Previous. Sets test_prev parameter to "current" or "previous". This parameter
determines whether responses to results query commands will be based on the current
interval or the previous interval.
Min. Abbr.
Arguments
test_pre
current:
Test status commands will return results from
the current test interval
previous:
Test status commands will return results from
the previous test interval
Example
test_prev current
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Remote Commands
test_prev?
Test Previous Query. Returns the current state of the test_prev command.
Min. Abbr.
test_pre?
Returns
Example
[current|previous]
test_prev?
TEST_PREV CURRENT
(command)
(response)
test_print
Test Print. This command causes the Analyzer to print a Test Summary report. This
report has the same basic format and contents as an End-of-Test report. If a test is in
progress, the report will be based on current interval results. If no test is in progress, then
the report will be based on results from the previous interval and will be an End-of-Test
summary.
Min. Abbr.
Arguments
Example
test_pri
none
test_print
test_report [eot|on_error|both|none]
Test Report. This command enables or disables End of Test and On Error reports.
Min. Abbr.
Arguments
test_r
eot:
on_error:
both:
End-of-Test reports are enabled.
On-Error reports are enabled.
Both End-of-Test and On-Error
reports are enabled
none:
Neither End-of-Test nor On-Error reports
are enabled.
Example
test_report both
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Remote Commands
test_report?
Test Report Query. Returns a character string indicating the current setup of the test
report parameter.
Min. Abbr.
Returns
test_r
[eot|on_error|both|none]
Example
test_report?
TEST_REPORT BOTH
(command)
(response)
test_squelch [on|off]
Test Squelch. Enables or disables squelching of On-Error reports.
Min. Abbr.
Arguments
test_sq
on:
On-Error reports will be squelched after 10 consecutive
reports, that is 10 consecutive seconds in which BER
is above the Test Error Rate threshold. On-Error
reports will then be automatically unsquelched
after five consecutive seconds in which BER is not
above the Test Error Rate threshold.
off:
On-Error report squelching is disabled.
Example
test_squelch on
test_squelch?
Test Squelch Query. Returns a character string indicating the current setup of the test
squelch parameter.
Min. Abbr.
Returns
test_sq?
[on|off]
Example
test_squelch?
TEST_SQUELCH ON
(command)
(response)
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Remote Commands
test_state [run|stop]
Test State. This command is used to start or stop the test measurement process.
Min. Abbr.
Arguments
test_st
run: starts the test measurement process. Will initiate an
untimed, timed, or repeat test depending on the setup
of test mode.
stop: Stops the test measurement process. Will terminate
untimed or repeat tests. Will also prematurely end
timed tests before "test length" has elapsed.
Example
test_state run
test_state?
Test State Query. Returns a character string indicating the current state of the test
process. A response of RUN indicates that a test is in progress. A response of STOP
indicates that no test is in progress.
Min. Abbr.
Returns
test_st
[run|stop]
Example
test_state?
TEST_STATE RUN
(command)
(response)
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Remote Commands
test_thres [v]
-v
Test Threshold. Used to set the test error rate threshold to the value: 1 x 10 . This
threshold determines which seconds are counted as Threshold Errored Seconds (TES).
It also determines when On-Error reports are generated.
Min. Abbr.
Arguments
test_t
v
<NR1>, in the range 2, 3, ..., 16. That is the test
error
rate threshold may be set in the range 10 to 10
-2
-16
.
Example
test_thres 12
test_thres?
Test Threshold Query. Returns the value v, indicating that the current test error rate
-v
threshold is set to 1 x 10 .
Min. Abbr.
Returns
test_t?
<NR1>
Example
test_thres?
TEST_THRES 12
(command)
(response)
indicating that the test error rate threshold
-12
is set to 1 x 10
.
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Remote Commands
WINDOW Setup Commands
win_bit_len [v]
v
Windows Bit Length. Sets BER window bit length parameter to 1 x 10 bits. This
parameter determines window length when WIN_MODE is set to BITS.
Min. Abbr.
Arguments
Example
win_bit_
v
<NR1>, in the range 8, 9, ..., 16.
win_bit_len 15
win_bit_len?
Windows Bit Length Query. Returns the value v, indicating that the BER window bit
v
length parameter is set to 1 x 10 bits.
Min. Abbr.
Returns
win_bit_?
<NR1>
Example
win_bit_len?
WIN_BIT_LEN 15
(command)
(response)
win_bits?
Window Bits. Returns the total number of bits evaluated so far in the BERwindow
interval.
Min. Abbr.
Returns
win_bits?
<NR1>
Example
win_bits?
WIN_BITS 49098302
(command)
(response)
win_error?
Windows Errors. Returns the total number of bit errors counted so far in the BER
window current or previous interval.
Min. Abbr.
Returns
win_e
<NR1>
Example
win_error?
WIN_ERROR 27
(command)
(response)
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Remote Commands
win_mode [bits|sec]
Windows Mode. Determines whether BER window length is determined by the
windows bits (pattern length) parameter or the windows seconds (time length) parameter.
Min. Abbr.
Arguments
win_m
bits:
sec:
selects the windows bits length parameter
selects the windows seconds length parameter.
Example
win_mode bits
win_mode?
Windows Mode Query. Returns the current BER window length mode.
Min. Abbr.
Returns
win_m
[bits|sec]
Example
win_mode?
WIN_MODE BITS
(command)
(response)
win_prev [current|previous]
Window Previous. Sets the WIN_PREV parameter to current or previous. This
parameter determines whether Analyzer responses to win_bits?, win_error?, win_rate?,
and win_time? queries will be based on the current window interval or the previous
window interval.
Min. Abbr.
Arguments
win_p
current
previous
selects the current window interval
selects the previous window interval
Example
win_prev current
win_prev?
Window Previous Query. Returns the current value of the WIN_PREV parameter.
Min. Abbr.
Returns
win_p
[current|previous]
Example
win_prev?
WIN_PREV CURRENT
(command)
(response)
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Remote Commands
win_rate?
Window Rate Query. Returns the BER measured in either the current window interval
so far, or the previous window interval, depending on the setup of WIN_PREV.
Min. Abbr.
Returns
win_ra?
<NR3>
Example
win_report [on|off]
Windows Report. This command enables or disables End-of-Window reports.
Min. Abbr.
Arguments
win_re
on
off
enables End-of-Window reports.
disables End-of-Window reports.
Example
win_report on
win_report?
Windows Report Query. Returns a character string indicating whether End-of-
Windows reports are enabled (on) or disabled (off).
Min. Abbr.
Returns
win_re?
[on|off]
Example
win_report?
WIN_REPORT ON
(command)
(response)
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Remote Commands
win_sec_len [s]
Windows Seconds Length. Sets the BER window seconds length parameter to the
duration indicated by the quoted string s.
Min. Abbr.
Arguments
win_s
s
<qstring>, in format "hh:mm:ss", where hh = hours (00 to
23), mm = minutes (00 to 59), and ss = seconds (00 to 59).
Example
win_sec_len 00:30:00
win_sec_len?
Windows Seconds Length Query. Returns a quoted string indicating the value of the
BER window seconds length parameter.
Min. Abbr.
Returns
win_s?
<qstring>
Example
win_sec_len?
WIN_SEC_LEN "00:30:00"
(command)
(response)
win_time?
Windows Time Query. Returns either the elapsed time in the current BER window so
far, or the duration of the previous BER window, depending on the setup of the
WIN_PREV parameter.
Min. Abbr.
Returns
win_t?
<qstring>, in the format "ddd-hh-mm-ss", where ddd = days (0 to
999), hh = hours (0 to 23), mm = minutes (0 to 59), and ss =
seconds (0 to 59).
Example
win_time?
WIN_TIME "000-01:00:00"
(command)
(response)
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Remote Commands
PRINT Setup Commands
print_enable [on| off]
Print Enable. This command turns the "master" Analyzer Print Enable parameter on or
off. When Print Enable is off, then no reports will be printed. When Print Enable is on,
then all enabled reports will be printed. Remember that individual reports will not print
unless they are enabled individually and Print Enable has been set to "on".
Min. Abbr.
Arguments
print_e
on
off
enabled reports will print.
no reports will print
Example
print_enable on
print_enable?
Print Enable Query. Returns the current state of the Print Enable parameter.
Min. Abbr.
Returns
print_e?
[on|off]
Example
print_enable?
PRINT_ENABLE ON
(command)
(response)
print_port [ parallel | gpib | serial ]
Print Port. This command selects the port on which all Analyzer reports will be printed.
Min. Abbr.
Arguments
print_p
parallel
gpib
serial
selects the rear-panel "PRINTER" port
selects the rear-panel "GPIB" (IEEE-488) port.
selects the rear-panel "RS-232C" port.
Example
print_port parallel
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Remote Commands
print_port?
Print Port Query. Returns the currently selected printer port.
Min. Abbr.
print_p?
Returns
Example
[ parallel | gpib | serial ]
print_port?
PRINT_PORT PARALLEL
(command)
(response)
print_string ["s"]
Print String. This command prints a character string s to the currently selected printer
port.
Min. Abbr.
Arguments
Example
print_s
"s"
a character string enclosed in quotes.
print_string "This is a test"
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Remote Commands
Audio Beeper Setup Commands
audio_rat_up and
audio_rat_dn
Audio Rate Up/Down (Default). This command pair is used to increment
(audio_rat_up) or decrement (audio_rat_dn) by one the exponent of the current error rate
threshold of the BER beeper.
Min. Abbr.
audio_rat_u
audio_rat_d
Arguments
Example
none
audio_rat_up
This command adds one to the exponent of the beeper BER
threshold.
audio_rat_up [v] and
audio_rat_dn [v]
Audio Rate Up/Down. This command pair is used to increment (audio_rat_up) or
decrement (audio_rat_dn) the exponent of the error beeper BER threshold by an amount
v. Note that because the exponent is negative, the audio_rat_up command decreases the
BER threshold while audio_rat_dn increases the threshold.
Min. Abbr.
audio_rat_u
audio_rat_d
Arguments
Example
v:
1, 2, 3, ..., 14.
audio_rat_up 9
The above example adds 9 to the exponent, for example changing
-3
-12
the audio rate threshold from 1 x 10 to 1 x 10
.
audio_rate [v]
-v
Audio Rate. Sets the BER threshold for the error beeper to 1 x 10 .
Min. Abbr.
Arguments
Example
audio_rate
v:
2, 3, ..., 16
audio_rate 9
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Remote Commands
audio_rate?
Audio Rate Query. Returns the current error beeper BER threshold.
Returns
Example
<NR1>
audio_rate?
AUDIO_RATE 9
(command)
(response)
audio_vol [v]
Audio Volume. Sets the volume of the error beeper to v, where v can range from 0
(off) to 4 (maximum volume).
Min. Abbr.
Arguments
Example
audio_vol
v:
0, 1, 2, 3, or 4
audio_vol 4
audio_vol?
Audio Volume Query. Returns a decimal number in the range 0, 1, 2, 3, or 4, that
represents the current error beeper .
Min. Abbr.
Returns
audio_vol?
<NR1>
Example
audio_vol?
AUDIO_VOL 4
(command)
(response)
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Remote Commands
audio_vol_up and
audio_vol_dn
Audio Volume Up/Down (Default). This command pair is used to increment
(audio_vol_up) or decrement (audio_vol_dn) the current error beeper volume by one
level.
Min. Abbr.
audio_vol_u
audio_vol_d
Argument
Example
none
audio_vol_up
audio_vol_dn
audio_vol_up [v] and
audio_vol_dn [v]
Audio Volume Up/Down. This command pair is used to increment (audio_vol_up) or
decrement (audio_vol_dn) the current error beeper volume by "v" levels.
Min. Abbr.
audio_vol_u
audio_vol_d
Argument
Example
v
<NR1>, 1, 2, 3, or 4
audio_vol_up 2
audio_vol_dn 2
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Remote Commands
Misc. Analyzer Commands
date ["yyyy-mm-dd"]
Date. Sets the current date in year-month-day format. Note that the argument is a
quoted character string.
Min. Abbr.
Arguments
date
yyyy year (NOTE: may be above 2000)
mm
dd
month (1, 2, ..., 12)
day (1, 2, ..., 31)
Example
date "2001-03-21"
date?
Date Query. Returns a quoted string that indicates the current date setup of the
Analyzer in year-month-day format.
Min. Abbr.
Returns
date?
<qstring>
Example
date?
DATE "2001-03-02"
(command)
(response)
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Remote Commands
time [s]
Time. Used to set the instrument's time of day clock.
Min. Abbr.
Arguments
ti
s
<qstring>, in the format "hh:mm:ss". where
hh = hours (00 ... 23), mm = minutes (00 ... 59), and
ss = seconds (00 ... 59).
Examples
time 16:30:02
time?
Time Query. Returns a quoted string indicating the current setting of the instrument's
time of day clock.
Min. Abbr.
Returns
ti?
<qstring>
Example
time?
TIME "16:30:11.45"
(command)
(response)
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Remote Commands
1 MB Option Commands
The following section identifies commands that are modified or added when the 1 MB
Option is installed.
Modified Commands
When the 1 MB Option is installed, the All_mem command will operate as before except
that it will not return any saved word patterns.
Replaced Commands
The standard GB1400 Generator and Analyzer command set includes the following
"word" commands:
word_bits; word_memory ; word_length ; word_mem_len
These commands are limited to creating and editing short word patterns, that is patterns
that are 8 or 16 bits in length. They will not work on long word patterns. Instead, long
word editing functions are performed using "byte" commands, which are added as part of
the 1 MB Option. Moreover, byte commands also work on short words. Therefore,
"word" commands have limited application in instruments equipped with the 1 MB Option.
However, "word" commands will still function in units equipped with the 1 MB Option.
This insures that a Generator or Analyzer equipped with the 1 MB Option can replace a
standard unit in automated applications designed to use standard (short word) commands.
Commands specific to I MB Option
When the 1 MB Option is installed all of the following commands are added to the
Generator and Analyzer command sets except for the byte_sync command, which is
added to only the Analyzer command set.
The following general rules apply to new 1 MB commands:
1. Commands used to edit long words execute properly only when received after an
edit_begin command and before an edit_end command. These include:
q byte_length
q byte_fill
q byte_block
q byte_edit
q byte_insert
q byte_delete
2. If a command includes a bit address argument [a], then [a] must be less than the
length, which can be specified by the byte_length command.
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Remote Commands
byte_block [a], [i], [b1], ..., [bn]
Byte Block. This command overwrites a block of i bits in the edit pattern, beginning at
address a, with the overwrite pattern indicated by bytes b1 through bn.
Min. Abbr.
Arguments
byte_b
a
<NR1>, the following ranges indicate the starting
address of the overwrite block.
0 to 131071 (1M mode)
0 to 65535
0 to 32767
(512K mode)
(256K mode)
0 to 16,383 (128K mode)
0 to 8191 (64K mode)
i
<NR1>, in the range 1 to 80, the number of bits to
overwrite. 10 Bytes maximum.
b1, ..., bn
<non-decimal numeric(s)> Indicating the bytes that
make up the overwrite pattern. Each byte may be in
the range #H00 to #HFF (hex), #Q000 to #Q377
(octal), or #B00000000 to #B11111111 (binary).
Example
byte_block 4096, 24, #HBB, #H10, #HFF
Note: The address "a" plus the number of bytes being changed ('i'/8) must be less than
the pattern length.
Note: n of "bn" must equal 1/8.
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Remote Commands
byte_block? [a]
Byte Block Query. Returns the hex., octal, or binary representation of the 80 bit section
of the edit pattern beginning with the bit at address a. Note that if there is no editing
session in progress, this command will return the indicated 80 bit section from the current
word pattern.
"a"
0 to 131071 (1M mode)
0 to 65535
0 to 32767
(512K mode)
(256K mode)
0 to 16,383 (128K mode)
0 to 8191
(64K mode)
Min. Abbr.
Response
byte_b?
[a], [i], [b1], ..., [b2]
in format: <NR1>, <NR1>, <non-dec. numeric(s)>
Example
byte_block? 500
BYTE_BLOCK 500, 16, #H12, #HF1
NOTE: If address [a] is within 10 bytes of the end of the pattern, then less than 10 bytes
will be returned. Also, if the last byte of the pattern is included in the requested block, and
this byte contains one or more unused bits, then these bits will be returned with a value of
0.
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Remote Commands
byte_delete [a], [i]
Byte Delete. This command deletes i bits from the edit pattern starting with bit a.
Min. Abbr.
Arguments
byte_d
<NR1>, in the range "a", the block of bits to be deleted
begins at this address.
a
0 to 131071 (1M mode)
0 to 65535 (512K mode)
0 to 32767 (256K mode)
0 to 16,383 (128K mode)
0 to 8191
(64K mode)
<NR1>, in the range 8 to 80, in steps of 8, this is the
number of bits to delete.
i
Example
byte_delete 512, 80
Note: The address "a" plus the number of bytes being changed ('i'/8) must be less than
the pattern length.
Note: n of "bn" must equal 1/8.
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Remote Commands
byte_edit [a], [b1]
Byte Edit. This command is similar to byte_block except that it can overwrite (edit) only
one byte at a time. The command overwrites 8 bits starting at address a.
Min. Abbr.
Arguments
byte_e
<NR1>, in the range "a", the address of the overwrite
byte.
a
0 to 131071 (1M mode)
0 to 65535 (512K mode)
0 to 32767 (256K mode)
0 to 16,383 (128K mode)
0 to 8191
(64K mode)
<non-decimal numeric> indicates the overwrite byte
pattern. May be in the range #H00 to #HFF (hex),
#Q000 to #Q377 (octal), or #B00000000 to
#B11111111 (binary).
b1
Example
byte_edit 1000, #Q320
byte_edit? [a]
Byte Edit Query. Returns the hex., octal, or binary representation of the C-bit section
of the edit pattern at address a.
Note that if there is no editing session in progress, this command will return the indicated
byte from the current word pattern.
Min. Abbr.
Response
Example
byte_e?
[a], [b1] in the format <NR1>, <non-decimal numeric>
byte_edit?
BYTE_EDIT 500, #H12
(command)
(response)
NOTE: If the returned byte is the last byte, and if this byte contains one or more unused bits,
then these bits will be returned with a value of 0.
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Remote Commands
byte_fill [i], [b1], [b2], ..., [bn]
Byte Fill. This command fills the entire edit pattern with a repeating i-bit pattern, b1, b2,
b3, ..., bn.
Min. Abbr.
Arguments
byte_f
<NR1>, in the range 8 to 80, in steps of 8, indicates the
number of bits in the fill pattern.
i
<non-decimal numeric(s)> indicating the contents of
the fill pattern. Each byte may be in the range: #H00
to #HFF (hex), #Q000 to #Q377 (octal), or
#B00000000 to #B11111111 (binary).
b1, ...,
bn
Example
byte_fill 16, #HAA, #HFF
byte_insert [a], [i], [b1], ..., [bn]
Byte Insert. This command inserts a pattern of length i, bits, starting at address a in the
edit pattern. The insert pattern is indicated by bytes b1, ..., bn.
Min. Abbr.
Arguments
byte_i
<NR1>, in the range "a", the insert pattern will be
inserted at this address.
a
0 to 131071 (1M mode)
0 to 65535 (512K mode)
0 to 32767 (256K mode)
0 to 16,383 (128K mode)
0 to 8191
(64K mode)
<NR1>, in the range 8 to 80, in steps of 8, the number
of bits to insert.
i
<non-decimal numeric(s)> Indicating the bytes that
make up the insert pattern. Each byte may be in the
range #H00 to #HFF (hex), #Q000 to #Q377 (octal),
or #B00000000 to #B11111111 (binary).
b1, ...,
bn
Example
byte_insert 1600, 32, #HFF, #HFF, #H00, #H00
(inserts the sequence FFFF0000 hex into the edit
pattern at address 1600, and increments
the edit pattern length by four bytes).
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Remote Commands
byte_length [m], [n]
Byte Length. This command sets the length of the edit pattern to m bytes plus n bits.
Min. Abbr.
Arguments
byte_l
m
<NR1>, in the range:
0 to 131072 (1M mode)
0 to 65536 (512K mode)
0 to 32768 (256K mode)
0 to 16,384 (128K mode)
0 to 8192 (64K mode)
n
<NR1>, in the range 0 to 7.
Example
byte_length 16384, 0
NOTE: If the number of whole bytes (m) is greater than 2047, then the number of added bits
(n) must be set to 0. If m is greater than 16384, then n must be even.
byte_length?
Byte Length Query. Returns the current length of the edit pattern in terms of whole
bytes plus up to seven additional bits. Note that if there is no editing session in progress,
this command will return the length of the current word pattern.
Min. Abbr.
Returns
byte_l?
<NR1>, <NR1>, indicating the number of bytes and the
number of additional bits.
Example
byte_length?
(command)
BYTE_LENGTH 100, 5
(response indicating an edit
pattern length of 805 bits)
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Remote Commands
byte_mode [n]
Byte_Mode. Controls the WORD storage mode. There will always be a Current Word
Buffer. In addition to that, there is 0 to 10 memory storage buffers. In different modes,
the buffers permit patterns of different lengths.
Arguments
n
64, 128, 256, 512, 1024
64
10 Word memory buffers of 64 kbits (locations 0 to 9)
6 Word memory buffers of 128 kbits (locations 0 to 5)
3 Word memory buffers of 256 kbits (locations 0 to 2)
1 Word memory buffers of 512 kbits (location 0)
128
256
512
1024 0 Word memory buffers of 1024 kbits
byte_mode 64
Example
byte_mode?
Returns the current Word storage buffer mode.
Response <NR1 Numeric>
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Remote Commands
byte_sync [n] (Analyzer only)
Byte Synchronization. This command sets the long-word pattern synchronization
threshold. This threshold does not apply to short-word patterns, or PRBS patterns. The
long-word synchronization threshold is set in terms of an integer, n, which corresponds to
a BER threshold. In the table below, the ratios of errors to bits corrrespond to the window
examined and the maximum errors for the threshold.
Level
BER
Ratio (errors/bits)
(256/8192)
1
2
3
4
5
6
7
8
9
3.1E-2
7.8E-3
1.9E-3
9.7E-4
4.8E-4
2.4E-4
1.2E-4
6.1E-5
3.0E-5
(256/32768)
(256/131072)
(256/262144)
(256/524288)
(256/1048576)
(256/2097152)
(256/4194304)
(256/8388608)
byte_s
Min. Abbr.
Arguments
Example
i
<NR1>, in the range 1 (highest BER) to 9 (lowest BER).
byte_sync 4
NOTE: This command is found in the Analyzer command set only.
byte_sync? (Analyzer only)
Byte Synchronization Query. Returns a single decimal digit which represents the
current long-word synchronization threshold.
Min. Abbr.
Returns
byte_s?
<NR1>
Example
byte_sync?
BYTE_SYNC 4
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Remote Commands
edit_begin [n]
Edit Begin. You must issue this command to the instrument before starting an editing
session. In effect this command loads the contents of a word memory location specified
by n into a scratch pad memory location. Once in the scratch pad memory it can be
edited, uploaded to the controller, or saved to the same or a different memory location.
You also must issue the edit_begin command before downloading a word pattern to the
instrument.
Min. Abbr.
Arguments
edit_b
n
<NR1>, a decimal number in the range -1 to 9, where -1
indicates the current word pattern and 0 through 9 indicate the
memory locations.
-1 only (1M and 512K modes)
-1 to 2 (256K mode)
-1 to 5 (128K mode)
-1 to 9 (64K mode)
edit_begin 2
Example
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Remote Commands
edit_cntrl?
Edit Control Query. This command returns a character string that indicates whether or
not a long-word (1 MB Option) editing session is in progress and if that session is under
local or remote control.
Min. Abbr.
Returns
edit_c
[local|remote|none], where:
local:
indicates a long-word editing session is in
progress under local (front panel) control
remote:
indicates a long-word editing session is in
progress under remote (RS-232C or GPIB)
control
none:
indicates that there is no long-word editing
session in progress
Example
edit_cntrl?
(command)
EDIT_CNTRL NONE
(response)
edit_end [n]
Edit End. You must issue this command to finish a 1 MB word editing session. This
command either moves the edited pattern from scratchpad memory to the current word
location, or saves the edited pattern into one of the instruments eight word memory
locations. You can also use this command to discard the edit pattern.
Min. Abbr.
Arguments
edit_e
n
<NR1>, a decimal number in the range -2 to 9, where -2 discards
the edited pattern, -1 copies the edited pattern to the current
word location, and 0 through 9 saves the edited pattern to the
indicated memory location.
-1 only (1M and 512K modes)
-2 to 2 (256K mode)
-2 to 5 (128K mode)
-2 to 9 (64K mode)
edit_end -1
Example
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Remote Commands
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Using GPIB, RS-232 Interfaces
This chapter describes the use of the GB1400 Bit Error Rate Tester Remote
Interfaces. Since the remote interfaces enable automatic testing, the user does
not have to complete any of the manual procedures necessary for front panel
operation. However, the user can write programs to conduct the test sessions.
Using the GPIB Interface
The GB1400 supports remote control through the GPIB interface bus connector
on the rear panel. The unit can be operated from the front panel and over the
remote interface simultaneously. All of the front panel functions can be controlled
over the GPIB interface, except `POWER.'
Remote commands sent to the GB1400 differ from front panel control. The
current operating mode is entered directly rather than through submenus.
GPIB Interface Device Settings
For proper GPIB Interface communication and handshaking, the GPIB controller
(system that controls the operation) and the device (GB1400) must have their
addresses and terminating characters set up before use.
Each instrument on the GPIB interface bus needs a unique INSTRUMENT
address, programmed by 'GPIB ADDR:' key. The INSTRUMENT address range
for the GB1400 is 0 - 30 decimal. The GPIB Message Terminator is set to either
EOI or EOL/LF. For EOI, the EOI line will be asserted when the last byte of a
message is transmitted. For EOI/LF, the last byte of the message will be the line
feed character, and the EOI line will be asserted with its transmission, using
Utility menu (F1) key.
Step 1: Press the GPIB ADDR, "GPIB xx" is displayed on the LCD.
Step 2: Press the left-most UP/DOWN key (INPUT) to select the desired GPIB
address "xx".
Step 3: Press GPIB ADDR a second time.
The BERT will then respond to commands sent to that INSTRUMENT address.
This will done without affecting the remote command processing.
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Using GPIB, RS-232
Interface Functions
The GB1400 is configured as a talker/listener. No controller functions are
implemented. As described in the IEEE-488 standards, the GB1400 supports the
following implementation:
SH1
AH1
T6
Complete source handshake
Complete acceptor handshake
Basic talker; serial poll, no talk only, unaddressed if
addressed to listen, no extended talker
Basic listener, no listen only, unaddressed if addressed to
talk, no extended listener
L4
SR1
RL1
PP0
DC1
DT0
C0
Complete service request
Complete remote/ local capability including local lockout
No parellel poll capability
Complete device clear capability
No device trigger capability
No controller capability
E2
Tri-state drivers used on DI0 lines for maximum data
transfer rate
GPIB Connector Pin-Outs
The GB1400 uses the standard D-type 24 pin GPIB connector located on the rear
panel. All signals and pins conform to the standard GPIB pin out protocol.
Programming GPIB Remote Commands
There are two types of remote commands for the GB1400:
·
·
Set commands (commands)
Queries commands (queries
The set commands force the GB1400 to take a specific action. The query
commands direct the GB1400 to return status information. The controller sends
commands to the GB1400 as strings terminated at EOI or EOI/LF characters.
These command lines can contain either a single command or multiple commands.
The command line may contain both queries and commands. Each individual
command within the command line must be separated by semi-colons (;),
parameters must be separated by comma (,). Hexadecimal parameters must be
preceded by a ‘#H’.
Each query command sent to the GB1400 will return one response. The response
may contain multiple response units (separated by semi-colons), however only one
EOI/LF response termination is sent by the GB1400 to the controller for each
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Using GPIB, RS-232
query command. The GB1400 responses commands will be either character
mnemonics (for example, INT or EXT) or numerics (Example: 200.0).
GPIB Numeric Responses
When responding with a numeric, the receiver specifies it as one of the following
types:
<NR1 Numeric>:
decimal integer
<NR2 Numeric>:
<NR3 Numeric>:
<Non-decimal Numeric>:
decimal real number without exponent
decimal real number with exponent
non-decimal number with leading #H (Hex), #Q
(Octal), #B (Binary) and always in the range of 0
to 255 decimal (for example, #H55)
GPIB Status Reporting
There is a status reporting function provided for the GPIB interface, which is
based on the SRQ (Service Request) and is defined in the ANSI/IEEE standard
488.2-1987. The implementation used by GB1400 for status reporting includes one
additional register from what is specified within the IEEE-488.2 standard.
Status Byte
There is a status byte which is used to define the SRQ status. The individual bits
within the status byte represent the different conditions which might cause the
request for service defined as follows:
Bits 1 to 3
Bit 4
Unused
(TSB) Test
Event Status
Bit
This is a summary of Test Event Status
Byte. It will be set whenever an enabled
Test event condition occurs
Bit 5
Bit 6
(MAV)
Set whenever there is output available for
the controller
Message
Available Bit
(ESB)
Standard
Event Status
Bit
This is the summary of the Standard Event
Status Byte. It will be set whenever an
enabled standard event condition occurs
Bit 7
Bit 8
(MSS) Master This is the Master Summary Status. It is a
Summary
Status Bit
summary of the status byte, so that
whenever one of the bits (TSB, MAV or
ESB) is set and it is also enabled (by the
Service Request Enable byte), the MSS bit
will set
Unused
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Using GPIB, RS-232
Service Request Enable
Different conditions for a service request can be individually enabled. The Service
Request Enable byte contains the enabling bits for the status byte. For a service
request to occur, either the TSB, MAV or ESB bit must be enabled. Each time
the GB1400 is powered on, this byte is RESET so that no bits are enabled. The bit
definition is the same as the status byte, except bit 7 is undefined.
Service Request (SRQ)
The status byte enables the creation of a service request. Whenever a condition
requiring service from the controller occurs and is enabled, the SRQ line is set. It
is reset after the controller finishes a serial poll of the GB1400 receiver, or when
all of the enabled service request conditions have stopped.
Standard Event Status Register
The ESB bit is the summary of the Standard Event Status Register. This byte has
an enabling byte similar to the Status Byte. Individual bits within the Standard
Event Status Register represent the different possible causes of a Standard
Event. The bit definitions for the Standard Event Status Register are as follows:
Bit 1
Operation
Complete
Only set following an *OPC command
Bit 2
Bit 3
Request Control Not Used
Query Error
Set under the following conditions:
·
·
·
when output has been requested from the
GB1400 and none is available
when a command is sent to the GB1400 and
GB1400 still has a message available
when output has been requested from the
GB1400 and an unterminated command has
been set to the GB1400
Bit 4
Bit 5
Device
Dependent Error
Set under the following conditions:
·
·
when input data is lost over the interface
when the input buffer overflows due to a too-long
command line without a terminator
Execution Error Set under the following conditions:
when a command parameter is out of range
when the command has too many or too few
parameters
when the command cannot be properly executed
due to a device condition
Bit 6
Command Error Set whenever the GB1400 receives an unrecognized
command, or invalid GPIB command
Bit 7
Bit 8
User Request
Power On
Not used
Set whenever the GB1400 is powered on
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Using GPIB, RS-232
Standard Event Status Enable Register
Different conditions within the Standard Event Status Register can be individually
enabled or disabled. The Standard Event Status Enable Register contains enabling
bits. Each time one of the event conditions or one of the enabling bits change, the
status of the ESB bit is re-evaluated. If any status bit is set and its corresponding
enable bit is set, the ESB bit is set also.
Each time the GB1400 is powered on, this byte is reset so that no bits are
enabled. The bit definition for the Standard Event Status Enable Register is the
same as it is for the Standard Event Status Register.
Test Status Event Register (Analyzer only)
The TSB bit is the summary of the Test Status Event Register. This byte has an
enabling byte which works in a similar manner to the above Status Byte. The
individual bits within the Test Status Event Register represent the different
conditions which might cause a Test Event. The bit definitions for the Test Status
Event Register are as follows.
Bit 1
End-of Window
condition
Set at the end of each window period
Bit 2
Bit 3
End-of-Test condition
Threshold Error
condition
Set at the end of each Test
Set whenever Test is running and Errored
Second occurs, where error rate is above Test
Error Rate Threshold
Bit 4
Synchronization Loss Set whenever SYNC LOSS occurs
condition
Bit 5
Bit 6
Phase Error condition Set whenever a Phase Error occurs
Auto Synchronization
complete
Set whenever AUTO SEARCH locks on a Data
Pattern
Bit 7
Bit 8
Not Used
Not Used
Test Status Event Enable Register (Analyzer only)
The different conditions within the Test Status Event Register can be individually
enabled and disabled. The Test Status Event Enable Register contains enabling
bits. Each time one of the event conditions or one of the enabling bits change, the
status of the TSB bit is re-evaluated. If any status bit is set and its corresponding
enable bit is set, the TSB bit will set. Each time the GB1400 is powered on, this
byte is reset so that no bits are enabled. The bit definition for the Test Status
Event Enable Register is the same as for the Test Status Event Register.
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Using GPIB, RS-232
GPIB Common Commands
The following commands are provided to use with GPIB status reporting, as
defined by IEEE 488.2 for service request:
*STB? *SRE *SRE? *ESR? *ESE *ESE? *CLS
Additional SRQ GPIB Commands (Rx only)
The following commands are provided to use with the Test Status SRQ feature:
TSE TSE? TSR?
IEEE-488.2 Programming Manual Requirements
Certain programming requirements are specified for GPIB interfaces by the
American National Standard Institute (ANSI) document, ANSI/IEEE Std. 488.2-
1987, which are detailed in this section.
Power-on settings
The GB1400 will restore the device settings to their same values from when it
was last powered off. No remote commands affect this. The only exception to
this is when the non-volatile RAM becomes corrupted (which should never
happen during normal operation). RAM corruption, if it occurs, will be displayed
on the unit’s LCD display. When this happens, the GB1400 will revert to its
factory-default settings.
Message Exchange
The message exchange options are as follows:
·
The input buffer is command line oriented. There is a new input buffer for
each command line or program message. The maximum input buffer length is
80 characters.
·
·
·
The only remote commands that return more than one response message unit
are: *lrn?; sta?; rdm?; rfm?; all?
All queries immediately generate their own response messages when parsed.
No queries wait until the responses are read for them to be generated.
No commands are coupled.
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Using GPIB, RS-232
Functional Elements
The IEEE 488.2 standard requires a list of the functional elements which are used
by the GB1400 receiver. These are the functional elements used in constructing
the remote commands that control the receiver. For more information, see the
IEEE 488.2 standard, sections 4.3, 7.1.1, and 7.3.3. From Tables 4.2 and 4.3 of
the IEEE 488.2 standard, the receiver does the following:
< program message>
< program message terminator>
<program message unit separator>
<query message unit>
< program message unit>
<command message unit>
< command program header>*
< program header separator>
< program data>
< query program header>*
< program data separator>
< decimal numeric program data>
<non-decimal numeric program data>
< character program data>
* <compound command program header> and <compound query program
header> are not handled.
Specific Command Implementations
The reset command “*rst” performs a device reset. As defined in the IEEE
488.2, it will:
·
reset the device settings to default settings, with the exception of stored
memory locations and any remote interface settings
·
·
Macros are not implemented in the GB1400, thus macros are ignored
force the receiver into Operation Complete Command Idle State (OCIS) and
Operation Complete Query Idle State (OQIS)
Self Test Query
This tests the receiver's basic functionality. The scope of the self test function is
limited.
Overlapped vs. Sequential Commands
All commands are sequential commands.
Operation Complete Message
All command actions are immediate (no overlapped commands), such that
operation complete is immediate.
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Using GPIB, RS-232
Using the RS-232 Interface Option
The GB1400 supports remote control through the RS-232C connector on the rear
panel The unit can be operated from the front panel and over the remote interface
simultaneously. Any unit changes made remotely are displayed on the front panel.
All of the front panel functions can be controlled over the RS-232C interface,
except “POWER.”
The remote commands sent to the GB1400 differ from front panel - the current
operating mode is entered directly rather than through sub-menus.
Commands are provided to read back stored data memory contents. Memory
contents can be read back and printed out for hardcopy archiving.
RS-232 Interface Device Settings
The RS-232C interface device settings are programmable through the front panel.
The following RS-232C parameters are programmable, along with the default
setting and other values.
Parameter
Baud, BPS rate
Parity
Data Size
Echo
Default
9600
Even
8
OFF
ON
Values
4800, 2400, 1200, 600, 300
None, Odd
7
ON
OFF
LF/CR, CR, LF
XON/XOFF
EOL
CR/LF
To change an RS-232C setting through the front panel.
Step 1: Press F1 to select menu mode.
Step 2: Select the RS232C menu choice.
Step 3: Select the desired setting type.
Step 4: Select the desired setting.
Step 5: Press F4 to set the selection
Step 6: Press F1 to EXIT.
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Using GPIB, RS-232
RS-232 Interface Hardware/ Handshaking Considerations
The remote interface consists of a 25-pin female D-type connector on the rear
panel. When using the RS-232C interface, connect the controller to the GB1400
with an appropriate 25-pin cable. The GB1400 is configured as an RS-232C DCE
(Data Circuit terminating Equipment). For a local (direct) connection to a DTE
device (most RS-232C controllers), connect the controller to the GB1400 with a
straight (non-null modem) cable. To connect to another DCE device, you need a
null modem to cross-connect signal pairs 2 & 3, 4 & 5, and 6 & 20.
Refer to the following table for RS-232C signal names, pinouts, and functional
descriptions.
Pin
Name
GND
RxD
TxD
CTS
RTS
DTR
GND
DSR
Function
1
2
3
4
5
6
7
20
Protective Ground
Received Data Input
Transmitted Data Output
Clear to Send (See note)
Request to Send (always high)
Data Terminal Ready (always high)
Signal Ground
Data Set Ready
All other pins
Not used
Note: Sent to the GB1400, a high-level indicates that external device is ready to
accept data from the unit. This pin must be high or open for the BERT to transmit
data. This pin is pulled high internally by 27K Ohm to +12V.
RS-232 Interface Testing
To test that the RS-232C interface is properly connected, attach a standard 25-pin
D-type connector cable between the RS-232C rear panel connector and the
controller, with the GB1400 turned off. Turn on the GB1400. The following
message should appear on the RS-232C controller’s screen, followed by the
GB1400>.
**** GB1400 RECEIVER VX.X
GB1400>
NOTE: V X.X indicates the unit's software version . The "GB1400>" line is a
prompt message indicating that the GB1400 is ready to accept a command.
If the message does not appear, check the following:
The cable may be defective.
The controller may be configured as DCE equipment. A null modem may be
needed.
The controller signal format or BAUD rate may not match the GB1400's settings.
Refer to the first part of this section for interface setting
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Using GPIB, RS-232
Programming RS-232C Remote Commands
There are two types of remote commands for the GB1400:
·
·
Set commands (commands)
Queries commands (queries
The set commands force the GB1400 to take a specific action. The query
commands direct the GB1400 to return status information.
Commands are entered one line at a time. Errors may be corrected while entering
a line, with the backspace key. A command string is terminated by a carriage
return, which transmits the string to the GB1400 and executes the command
string. All valid commands are executed. Incorrect or unsupported commands are
responded to by an error message. RS-232C error messages follow after this
section.
These command lines can contain either a single command or multiple commands.
The command line may contain both queries and commands. Each individual
command within the command line must be separated by semi-colons (;),
parameters must be separated by comma (,). Non-decimal numeric parameters,
Hexadecimal, Octal, and Binary must be preceded by a ‘#H’, ‘#Q’, or ‘#B’,
respectively. The entire command name does not have to be completely entered
for the command to be recognized as valid. There is a minimum valid length
associated with each command, which is the length that makes it unique from all
other commands.
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Using GPIB, RS-232
RS-232C Error Messages
All RS-232C remote commands received by the GB1400 are checked for
command validity and appropriate parameters (parameters listed with commands
within brackets [ ]). All valid command strings are executed. Incorrect command
strings are responded to with error messages
Error Message
Error
“*** Input Lost”
“*** Input Buffer Overflow”
Input data lost over interface
Input buffer overflow, command line
too long without terminator
Command not found
“*** Command Mnemonic Not
Found”
“*** Invalid Command for Interface”
Command found, but not valid for this
interface
“*** Invalid Command Type”
Command mnemonic found, but
command issued incorrectly: missing,
or added, '?' on end of command
Missing parameter
Too many parameters or training
garbage at end of command
Parameter invalid
“*** Too Few Parameters”
“*** Too Many Parameter”
“*** Invalid Parameters”
“*** Parameter Out of Range”
“*** Parameter Not in Set”
Parameter out of range
Parameter not one of the values
specified for the command
Parameter string too long
Parameter separator, ‘;’, is missing or
command line is terminated following
separator
“*** Invalid String Length”
“*** Parameter Separator”
“*** Command Execution Error”
“*** Out of Memory”
"*** Invalid Hexadecimal Parameter
Command not executed properly
Processor out of memory
Parameter not in hexadecimal format
or more than two hexadecimal
characters
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Using GPIB, RS-232
D-12
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p
Customer Acceptance Test
For
GB1400 Generator & Analyzer
NOTICE TO ALL PERSONS RECEIVING THIS DOCUMENT
THIS DOCUMENT IS ONLY CONDITIONALLY ISSUED, AND NEITHER RECEIPT NOR POSSESSION
THEREOF CONFERS OR TRANSFERS ANY RIGHT IN, OR LICENSE TO USE, THE SUBJECT MATTER
OF THE DOCUMENT OR ANY DESIGN OR TECHNICAL INFORMATION SHOWN THEREON, NOR ANY
RIGHT TO REPRODUCE THIS DOCUMENT OR ANY PART THEREOF, EXCEPT FOR MANUFACTURE BY
VENDORS FOR TEKTRONIX AND FOR MANUFACTURE UNDER THE CORPORATION’S WRITTEN
LICENSE, NO RIGHT TO REPRODUCE THE DOCUMENT IS GRANTED UNLESS BY WRITTEN
AGREEMENT WITH OR WRITTEN PERMISSION FROM THE CORPORATION.
Revision History
Date
Description
Pages Affected
9/29/94
9/3/96
Initial Release
Whole Document
Whole Document
Change Name to Tektronx
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Performance Verification
Performance Verification
The following tests verify that the GB1400 Generator & Analyzer achieve their specified
performance. These instruments are not user-adjustable. If the GB1400 needs repair,
return it to Tektronix.
Recommended Test Equipment
The recommended test equipment needed to verify performance is listed below.
Description
Specification
GB1400 Generator
GB1400 Analyzer
Coaxial SMA cables
Standard Instrument
75 Ohm option
equal length
six each 50 Ohm
four each 75 Ohm, two each 50
Ohm
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Performance Verification
Functional Test
To functionally test the GB1400, connect the Generator to the Analyzer and confirm
their correct operation as described below.
Note
In these procedures, the Generator and Analyzer are returned to their default
settings. The word memories will be reset. If you have entered word patterns
that you do not want to lose, use a GPIB or RS-232C controller to save them
before beginning these procedures.
q Step 1: Make connections appropriate to the options installed as follows:
Connections for Functional Test
Option
From
To
Comment
Standard Instrument
TX Clock
RX Clock
RX Not Clock
RX Data
50 Ohm, SMA coax
50 Ohm, SMA coax
50 Ohm, SMA coax
50 Ohm, SMA coax
50 Ohm, SMA coax.
TX Not Clock
TX Data
TX Not Data
TX Clock
RX Not Data
RX Clock
RX Not Clock
RX Data
75 Ohm Option
Use SMA to BNC
adapters and 75 Ohm
BNC coaxial cables
TX Not Clock
TX Data
TX Not Data
RX Not Data
See Figure 1 for Setup of Functional Test.
q Step 2: Reset both the Generator and Analyzer to their factory default settings.
Press the ‘CLEAR’ key in the PATTERN section, the ‘MSB(1)’ key and the ‘VIEW
ANGLE’ key, and hold down all three keys while cycling the power.
The message DEFAULT SETTINGS should appear briefly on the display of each unit,
followed by the GB1400 logo, before the functional display appears.
q Step 3: At the Generator, verify that error injection is off (you should see ERR OFF
on the display). If error injection is on, press the ‘SINGLE’ key in the ERROR
INJECT section to turn it off.
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Performance Verification
gigaBERT-1400TRANSMITTER
Data
Not Data
OUTPUT
Clock
Not Clock
DATA THRESHOLD (on rear panel)
gigaBERT-1400RECEIVER
Not Clock
Clock
Data
Not Data
Figure 1 -- Setup for Functional Test of Standard Instrument
q Step 4: At the Generator, verify that PRBS is selected (the PRBS LED light, in the
PATTERN, section, should be on.) If not, press the ‘PRBS’ key to select it.
q Step 5: At the Analyzer, press the ‘CLEAR’ key in the ERROR DETECTION section
and the ‘CLEAR’ key in the ERROR HISTORY section to clear the error display and
the error history LED lights. All four history LEDs should be off.
Because the Analyzer defaults to Autosearch mode, the Analyzer and the Generator are
now linked and synchronized. The following checks will confirm the functionality of the
units.
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Performance Verification
Confirmation of Frequency Function
q Step 6: In the Generator CLOCK section, the FREQUENCY LED should be on. If it
is not, press the ‘FREQUENCY’ key to select it.
q Step 7: Use the Generator CLOCK up/down keys to change the output frequency.
q Step 8: Check that the frequency displayed by the Analyzer matches the Generator
output to within ± 0.1 MHz. (Note that the resolution of the Analyzer is 0.01 MHz and
that the resolution of the Generator is 0.001 MHz.
q Step 9: At the Generator, use the ‘STEP’ key to select another frequency step size
(note the placement of the underscore on the Generator frequency display), and
repeat steps 7 and 8 at this step size.
q Step 10: Repeat steps 7 through 9 for all step sizes.
Confirmation of Selectable Data Patterns
q Step 11: In the Generator PATTERN section, verify that the PRBS LED light is on.
If not, press the PRBS key to select it.
q Step 12: Press the Generator PATTERN up/down keys to select PRBS pattern PN7.
q Step 13: Verify that the Analyzer displays the same PRBS pattern as the Generator.
q Step 14: At the Analyzer, press the ‘CLEAR’ key in the ERROR HISTORY section.
q Step 15: Verify that the four ERROR HISTORY LEDs are off and stay off.
q Step 16: At the Generator, use the PATTERN up/down keys to select the next PRBS
pattern.
q Step 17: Repeat steps 13 through 16 for each of the five PRBS patterns.
q Step 18: In the Generator OUTPUT section, press the ‘INVERT DATA’ key. The
INVERT DATA LED will light.
q Step 19: Verify that the INVERT DATA LED in the Analyzer INPUT section is also
on.
q Step 20: Repeat steps 12 through 17, noting that INV is displayed after the PRBS
pattern on the Analyzer display.
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Performance Verification
Confirmation of Generator Output Data Level Change
In this part of the functional test procedure, you will verify that the Analyzer threshold
responds correctly to the sample values of baseline offset and amplitude in the
Generator output. The sample values and threshold limits are summarized in the
following Data Levels table. Repeat steps 21 through 27 for each row of the Data Levels
table.
Note
Values in the following table are repeated; the purpose of this test is to
determine that the GB1400 responds correctly to changes in data level. You
do not need to read the results except at Step 26.
Data Levels
Generator Baseline Offset
Generator Amplitude
Analyzer Threshold Limits
-0.70 to -0.30
-1.00
0.00
1.00
1.00
2.00
0.30 to 0.70
-1.00
-0.20 to 0.20
q Step 21: Connect the cable to DATA THRESHOLD on the rear panel of the
Analyzer.
q Step 22: In the Generator OUTPUT section, the DATA LED should be on. If not,
press the ‘DATA’ key. The INVERT DATA LED should be off. If it is not, press the
key to turn it off.
q Step 23: Use the Generator BASELINE OFFSET up/down keys to set the baseline
offset value shown in the Generator Baseline Offset column of the Data Levels table.
q Step 24: Use the AMPLITUDE up/down keys to set the amplitude to the value
shown in the Generator Amplitude column of the Data Levels table.
q Step 25: At the Generator, select another PRBS pattern (using the PATTERN
up/down keys) to initiate a resynchronization by the Analyzer.
q Step 26: Select the PRBS pattern PN7.
q Step 27: At the Analyzer, verify that once the green LOCK LED in the SYNC section
lights, the displayed threshold is between the limits shown in the Analyzer
Threshold Limits column of the Data Levels table. Cycle through all five PRBS
patterns (PN7, PN15, PN17, PN20, and PN23) and verify that the Analyzer
synchronizes on each pattern.
q Step 28: At the Analyzer, press the CLEAR button in the ERROR HISTORY section
to ensure than the SYNC LOSS LED is off.
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Performance Verification
Confirmation of Error Injection Rates
q Step 29: In the Analyzer ERROR DETECTION section, press the ‘DISPLAY
SELECT’ key until there is an ¥ (infinity) symbol on the display preceding the error
rate.
q Step 30: At the Analyzer, press the ‘CLEAR’ key in the ERROR HISTORY section,
and press the ‘CLEAR’ key in the ERROR DETECTION section to clear the history
LEDs and error rate display.
q Step 31: In the Generator ERROR INJECTION section, press the ‘SINGLE’ key and
confirm on the Analyzer the BIT LED (in the ERROR HISTORY section) lights and
that the displayed error total increases by one each time you press the ‘SINGLE’ key.
Press this key at least 20 times.
Note
Press the ‘SINGLE’ key briefly. If you hold it down, the Generator injects
errors repeatedly into the data stream.
q Step 32: In the ERROR HISTORY section, press the ‘CLEAR’ key to clear the
history LEDs.
q Step 33: In Generator ERROR INJECTION section, press the ‘RATE’ key. ERR 1E-7
will appear on the display. The ERROR INJECTION LED should be on steadily.
q Step 34: In the Generator ERROR DETECTION section, press the ‘CLEAR’ key to
clear the totalize error display.
q Step 35: Wait 15 seconds, then confirm that the error rate displayed on the Analyzer
matches the Generator injected error rate and that the Analyzer BIT LED in the
ERROR HISTORY section is lighted.
q Step 36: In the Generator ERROR INJECTION section, press the ‘RATE’ key once to
select the next error rate.
q Step 37: Repeat steps 33 through 35 until all Generator error rates have been
verified and EXT appears on the Generator display. Press the Generator ‘ERROR
RATE’ key once more to turn off error injection.
q Step 38: Look straight at the Generator LCD panel. Depress the VIEW ANGLE
button until you see the darkest digits. Change the vertical angle from which you
view the display and adjust the clarity by depressing the VIEW ANGLE adjust
button. This is to verify that the contrast of the display can be optimized for the
user’s viewing angle.
q Step 39: Repeat Step 37 for the Analyzer.
q Step 40: Set the Generator and the Analyzer to Factory Default settings. Verify that
the Analyzer SYNC LOCK light illuminates. Push the CLEAR key in the ERROR
HISTORY section. Record the delay value shown on the display (lower left display
area) for later use. De-select AUTOSEARCH on the Analyzer. Press the ‘DELAY’ key
in the input section of the Analyzer. Vary the delay using the ‘UP’ and ‘DOWN’ arrow
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Performance Verification
keys in the input section of the Analyzer until the PHASE light in the ERROR
HISTORY section illuminates. Manually return the Analyzer delay setting to that
recorded above. Verify that the PHASE light can be extinguished by the ‘CLEAR’
key.
Confirmation of Selectable Analyzer Terminations
q Step 41: Set the Generator and Analyzer to Factory Default Settings. Confirm that
the Analyzer F2 LED is not lighted.
q Step 42: Push the Analyzer V-TERM button and confirm that the LCD displays
GND.
q Step 43: Perform the following actions for each termination listed:
a) Select the Analyzer termination by using the ‘UP’ and ‘DOWN’ arrow keys in
the INPUT section.
b) On the Generator, select PN15, wait a few seconds, then select PN7. Use the
‘UP’ and ‘DOWN’ arrow keys to select the different PN values.
c) Wait for the Analyzer LOCK light to come on.
d) Confirm the Analyzer threshold display falls within the limits shown in the
Termination Threshold Limits table.
e) Press F2 on the Analyzer to select CLOCK inputs and confirm that the F2
LED is lighted, and repeat steps a) through d).
Note
The threshold limits listed assume that the Generator is set to default
Amplitude and Baseline Offset.
Analyzer Termination Threshold Limits
Analyzer Termination
50 Ohm to GND
50 Ohm to -2 V
AC
Analyzer Threshold Limits
0 V ± 300 mV
-1.0 V ± 300 mV
0 V ± 300 mV
q Step 44: Set the Generator and Analyzer to Factory Default Settings.
q Step 45: Disconnect the cable from the DATA THRESHOLD on the rear panel of the
Analyzer and connect it to NOT DATA on the front panel of the Generator.
q Step 46: Select PN15 on the Generator.
q Step 47: Verify that the Analyzer LOCK light illuminates.
q Step 48: Repeat Steps 45 and 46 for all PN values.
E-8
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Performance Verification
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Performance Verification
Confirmation of Buttons and Indicators
q Step 49: Reset both the Generator and Analyzer by cycling the power.
q Step 50: Verify the following Generator LEDs.
Section
ON
OFF
CLOCK
FREQUENCY
RECALL
SAVE
EXT
PATTERN
PRBS
WORD
RECALL
SAVE
WORD LENGTH
F1 - F4
Bits 1 - 8
CLOCK
OUTPUT
DATA
INVERT DATA
RATE
ERROR INJECT
Left Side
PANEL LOCK
GPIB ADDR
LOCAL
q Step 51: Verify the Generator LEDs and buttons operate by toggling the following
buttons and observing the LEDs turn ON and OFF.
Section
LED/Button
Indicator
Left Side
PANEL LOCK
GPIB ADDR
ON - OFF
ON - OFF
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Performance Verification
q Step 52: Verify the Analyzer LEDs and buttons operate by toggling the following
buttons and observing the LEDs turn ON and OFF.
Section
LED/Button
Indicator
Left Side
PANEL LOCK
ADDR
ON - OFF
ON - OFF
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Default Settings
This appendix lists factory default settings for the GB1400 Generator and
Analyzer.
These are the value for the various operating parameters, when the unit leaves the
factory. These settings can be changed by the user, and stored in non-volatile
RAM. Should the non-volatile RAM be corrupted (due to battery failure), the
unit will reset all settings as listed here and the message 'RAM CORRUPTION'
will appear on the display for a few seconds to note that all settings are reset.
Returning to Factory Default Settings
Resetting the unit to Factory Default Settings can be done in two ways: through
front panel key sequence; or remotely through the GPIB interface.
How to Recall Factory Default Settings
Using Front Panel Controls
Use the following procedure to recall the factory default settings of the Generator
or Analyzer using front panel controls:
1. Turn instrument power off.
2. While holding down the WORD CLEAR, BIT 1, and VIEW ANGLE keys
simultaneously, turn instrument power back on.
3. After you see the message Default Settings appear in the display, release the
three keys. In a few seconds the normal display format will appear and the
instrument will be in its default setup.
Via Remote Control
To return the Generator or Analyzer to its factory default settings via remote
control, issue the *rst command. Note that this command also returns the
instrument to the Operation Complete Command Idle State and the Operation
Complete Query Idle State. This command does not change the WORD memory
contents.
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Default Settings
Generator (TX) Factory Default Settings
CLOCK
External Clock Source INT
Frequency
1405.0 MHz
Frequency Memory
0
720 MHz
360 MHz
180 MHz
90 MHz
1
2
3
4
45 MHz
5
1360 MHz
680 MHz
340 MHz
170 MHz
85 MHz
6
7
8
9
Frequency Step Size
1000.0 MHz
Data Pattern
7
PRBS pattern
PN 7 (2 -1)
AA 55
AA 55
PRBS
OFF
Word memory (all ten)
Programmable Data Pattern
Current Pattern Setting
Data Invert
Word Order
LSB
CLOCK/ DATA Outputs
Output Clock Amplitude
Clock Baseline Offset
Output Data Amplitude
Data Baseline Offset
Error Injection Rate
1.50 V
-0.75 V
1.50 V
-0.75 V
OFF
F-2
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Default Settings
Remote Interfaces
Remote mode
local
GPIB address (Generator)
GPIB Bus
15
TALK_LISTEN
EOI/LF
BERT1400>
9600
GPIB terminator
RS-232C prompt
RS-232C baud rate
RS-232C parity
even
RS-232C data size
RS-232C EOL
8 bits
CR/LF
OFF
RS-232C echo
RS-232C prompt line feed
OFF
MISC.
View Angle
Panel Lock
Response Header
0
OFF
ON
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Default Settings
Analyzer (RX) Factory Default Settings
Clock, Data, and Reference Data Inputs
Input data delay
0 pS
Input data threshold
Reference Data Delay
Reference Data Threshold
Data Termination
0.00 volts
0 pS
-1.50 V
GND
Clock Termination
GND
Reference Data Termination
GND
Data Pattern
7
PRBS pattern
PN 7 (2 -1)
Word memory (all ten)
Programmable Data Pattern
Current Pattern Setting
Data Invert
AA 55
AA 55
PRBS
OFF
Reference Data Mode
Word Order
OFF
LSB
Auto Search/Pattern Synchronization
Auto Search
ON
Auto Search Delay Mode
Auto Search Data Samples
Auto Search Data BER Threshold
Synchronization Disable
Error display select mode
FAST
10E+7
10E-6
OFF
TOT
Error Beeper
Audio volume
0 (off)
1E-3
Audio error rate threshold
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Default Settings
Time and Date
Date
Time
1-1-1999
00:00:00.0
Printer
Port
parallel
on
Print enable
Current BER
Mode
Seconds
1.0E+9
Bits
Seconds
00:00:01
CURRENT
OFF
Previous Remote Status
Report Enable
Test Parameters
Test Mode
TIMED
00:00:30
ON ERROR
1.0E-05
OFF
Test Length
Test Report Enable
Test Error Rate Threshold
Test Squelch
Previous Remote Status
Test Status Event Enable
PREVIOUS
0
Remote Intefaces
Remote Mode
LOCAL
14
GPIB address
GPIB Off Bus Capability
GPIB Terminator
RS-232C Prompt
RS-232C Baud Rate
RS-232C Parity
OFF
EOI/LF
BERT1400>
9600
EVEN
8 Bits
CR/LF
OFF
RS-232C Data Size
RS-232C EOL
RS-232C Echo
RS-232C Prompt Line-Feed
OFF
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Default Settings
MISC.
View Angle
Panel Lock
Response Header
0
OFF
ON
F-6
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Cleaning Instructions
Clean the GB1400 often enough to prevent dust and dirt from accumulating. Dirt
acts as a thermal insulator, preventing effective heat dissipation, and can also
provide high-resistance leakage paths between conductors or components in a
humid environment.
Cleaning the Exterior
Clean the dust from the outside of the instrument with a soft, clean cloth or small
brush. A brush is especially useful for removing dust from around the buttons
and connectors. Remove hardened dirt with a soft cloth dampened with a mild
detergent and water solution. Do not use abrasive cleaners.
Cleaning the CRT
Clean the light filter and CRT face with a soft, lint-free cloth dampened with
denatured alcohol. Do not use abrasive cleaners.
Cleaning the Interior
Interior cleaning and maintenance should be performed by qualified service
personnel only.
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Cleaning Instructions
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Pattern Editor Requirements and Features
Version 1.10 (9/13/96)
Before You Begin:
Before installing this program, it is suggested that you make a copy of this disk
and store it away in a safe place. To protect against accidentally overwriting any
files on this disk, slide the write protect tab on the back of the disk to the protect
position.
To Install MLPE:
1) Start Microsoft Windows.
2) In the FILE pulldown menu, choose RUN.
3) Type A:\SETUP or B:\SETUP.
4) Choose the OK button.
5) The program will install and create a new Program Manager group.
6) The README document is this document.
7) The installation is complete.
What is MLPE?
MLPE is a specialized pattern editor that can be used with Tektronix
gigaBERT700/1400 series and packetBERT200 BERT products. It allows the
user to create, store, edit, and transfer user defined and created patterns to and
from the BERTS.
Patterns can be created in several different formats and easily converted from one
format to another. The editor allows multiple files to be open at a time to make
editing and transferring data between files easier. See the list of features
described later in this document.
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Pattern Editing Software
Minimum Requirements:
Microsoft Windows 3.1 or later running on a 386 or faster machine with 4 Mb of
memory, For reasonable speed, a 486 DX or DX2 with at least 8 Mb of memory.
At least 2 Mb of free hard disk space.
gB700 Tx or Rx with 128K memory.
gB1400/1600 Tx or Rx with at least 256K memory.
A PB200.
One free RS-232 port or a National Instruments GPIB card with associated driver
and software.
List of Features
·
Editing capability in excess of 1 Mb. File size is in increments of 1 bit.
·
Files can be displayed, edited, and saved in Hex, Decimal, Octal, or Binary
formats.
·
Data can be saved or displayed LSB (Least Significant Bit) or MSB (Most
Significant Bit) first.
·
·
Files saved in one format can be converted to any of the other three formats.
Multiple editing windows can be open simultaneously to allow working on
several files at once.
·
The editor runs under Microsoft Windows with full Windows printing
capability.
·
·
·
Extensive built-in help.
Data can be uploaded to a gB700/1400/1600 Tx or Rx via RS-232 or GPIB.
Uploaded data can be saved in any memory location for any memory
configuration, even while the instrument is performing tests.
·
·
·
Data can be downloaded from a gB700/1400 Tx or Rx via RS-232 or GPIB.
Downloaded data can be saved to disk for safe keeping or later editing, even
while the instrument is performing tests.
Data can be saved to disk and read from disk in a format compatible with the
PB200, both current single file per disk and future multiple files per disk
formats.
The editor has full cut, paste, and copy facilities along with a last action
delete UNDO.
·
·
The editor has full find and replace functions.
Replaced data can be a different length than the data it is replacing.
What the editor cannot do:
H-2
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Pattern Editing Software
·
·
The editor uses a proprietary editor and therefore cannot share data with
other applications via the Clipboard.
The editor will not work with the GB660.
List of Files on this Disk
SETUP.EXE
SETUP.INS
README.DOC
MLPE.Z
MLPE.INI
MLPE.BMP
FPGRID10.VBX
Please verify that the above files are on this disk. If any are missing, please
contact Tektronix.
If you are using an alternate shell, such as Norton Desktop
In some cases the program will not install properly if an alternate shell, such as
Norton Desktop is used as your Windows shell. If the program gives error
messages, try installing the program using the standard Windows
PROGMAN.EXE shell. If the installation proceeds normally without any errors
but the program fails to run properly, check the following:
If you are using Norton Desktop 3.0, in the Tektronix program group select
(single mouse click) the Pattern Editor icon and then select PROPERTIES in the
GROUP menu. Select the ADVANCED icon. If the default path and directory
was chosen for installation, see if the listed STARTUP DIRECTORY shown is:
(drive on which Windows is installed):\MLPE\
If there is a "\" after MLPE then edit the entry to remove it.
The correct entry should look like the following:
(drive on which Windows is installed):\MLPE
Choose OK
The same may have to be done for the README icon if an error message
indicating that the README cannot be found.
The program will run properly now.
If the program should stop working
If the program has been installed and was working properly and then at a later
time fails to run properly, check to see if the "MLPE.INI" file in the WINDOWS
GB1400 User Manual
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Pattern Editing Software
directory is still there and is not corrupted. If it is not there, copy the MLPE.INI
file from the MLPE directory to the WINDOWS directory. See if the program
runs properly. If it is there, it may possibly be corrupted. Rename the file that is
there to MLPE.SAV and copy the MLPE.INI file from the MLPE directory to the
WINDOWS directory. if the program runs properly, delete the MLPE.SAV file
from the WINDOWS directory.
At any time, should any part of the program be corrupted or accidentally deleted,
the program can be re-installed.
RS-232 Cabling
If you are using the Editor with a gigaBERT700/1400/1600 and want to use RS-
232 to Upload or Download patterns, your RS-232 cable should be wired as
shown below:
gigaBERT RS-232 pin number 25 pin Comm Port
9 pin Comm Port
2
3
4
5
6
7
2
3
4
5
6
7
3
2
7
8
6
5
All other pins are not used.
GPIB
This program has been designed to use National Instruments GPIB hardware. It
may not work, or work properly with other brands of hardware.
Program Exclusivity
When running the Tektronix Pattern Editor it is suggested that there be no other
Windows programs running at the same time in the background. The normal
baud rate for operating the program is 9600 baud and other applications that are
running at the same time could cause some transferred data to be dropped. To
avoid lost data, close any other background applications so that Windows can
devote maximum time to the Editor.
H-4
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Pattern Editing Software
Saving patterns
If you open an existing saved pattern from disk and make changes to it, you will
be reminded to save the changes before you can close the file or exit the program.
If you receive a pattern from a gigaBERT to the Tektronix Pattern Editor you
must remember to save the file to disk before closing the file or exiting the
program. The program will not remind you to do so.
Depending on the format selected, if you attempt to save a file with any cells not
completely filled, the Editor will automatically insert zeros to complete the cell.
For example, if the HEX format is chosen and the last cell has an entry of "5", the
editor will save the cell with an entry of "05".
If a pattern of more or less than whole bytes is saved, the partial byte will be
saved with a whole byte entry whose needed bits are correct and the excess being
set to zero(s).
The BACKSPACE key works only within a cell.
Sending Patterns to or from a gigaBERT
Although you can save a pattern with a bit order of either LSB or MSB, you must
set the gigaBERT separately to reflect the correct order. The program does not
automatically set, or read, the gigaBERT to match the order of the file being sent.
If you should have a problem sending a pattern to a gigaBERT or receiving a
pattern from a gigaBERT, there may be a problem with the identification string
that is stored in the gigaBERT. Please consult the remote commands section of
the respective manual for the instrument. Normally, unless you change the
identification strings and prompt, they will remain at the default setting.
Another method for restoring the correct gigaBERT identification string and
prompt is to revert the gigaBERT to its default factory configuration. Reverting
the instrument to its default condition will destroy any saved patterns and clock
frequencies (Tx). To do this, turn the instrument off and then do the following:
For the gB1400 Transmitter: Simultaneously hold in the OUTPUT Clock and
PATTERN Clear buttons and turn the instrument on.
For the gB1400 Receiver: Simultaneously hold in the ERROR DETECTION
Clear and PATTERN Clear buttons and turn the instrument on.
For the gB700 Transmitter or Receiver: Simultaneously hold in the PATTERN
MSB, PATTERN Clear, and VIEW ANGLE buttons and turn the instrument on.
Hold the buttons in until RAM CORRUPTION or DEFAULT SETTING shows
in the display. Retry sending or receiving a pattern.
For help
Double click on the Context Help icon (The arrow and ?).
Corrections to the HELP information
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Pattern Editing Software
The HELP system indicates that only "filename.pat" files can be opened. This is
not true. Although ".pat" is the default extension and should be used for saving
all gigaBERT files, there may be different extensions that may be used for the
packetBERT200 depending on the version of firmware of the instrument. All
possible filename extensions are listed in the "List of File Type" box in the File
Open and File Save menus. Consult your packetBERT200 manual for filenames
that are valid.
To Remove the Tektronix Pattern Editor
1) Start Windows and remove the Tektronix group and all of its entries.
2) Save the configuration.
3) Open File Manager
4) Delete the following:
The MLPE directory and PATTERNS sub directory and all entries in
each.
Delete the MLPE.INI file in the WINDOWS directory.
5) The program edits the PATH statement in the AUTOEXEC.BAT file to add
the WINDOWS\SYSTEM directory to the path. You can edit the file to remove
this statement, or leave it.
There are no other files or changes made by the program.
NOTE:
For technical support or questions pertaining to the installation of this program,
call Tektronix at 800-643-2167 or 978-256-6800.
Microsoft Windows is a trademark of Microsoft Corporation.
National Instruments is a trademark of National Instruments Corporation.
H-6
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Pattern Editing Software
WARNING
Read License Agreement Before Opening
Tektronix / Microwave Logic Products
Copyright ã Microwave Logic, Inc. All Rights Reserved
Part Number 9508-1388
Version 1.0
IMPORTANT
READ BEFORE OPENING SEALED WRAPPER
This software is provided under license from Microwave Logic, Inc. Retention of this program for more
than (30) days, use of the program in any manner, or opening the sealed wrapper surrounding the
program constitutes acceptance of the license terms.
CAREFULLY READ THE ENCLOSED SOFTWARE LICENSE AGREEMENT
BEFORE OPENING THE SEALED WRAPPER SURROUNDING THE PROGRAM.
If you cannot agree to the license terms, promptly return the unopened package to Microwave Logic for a
full refund. Contact the nearest Microwave Logic Field Office for return assistance.
ã Copyright 1995 Microwave Logic, inc. Unpublished-rights reserved under the copyright laws of the
United States RESTRICTED RIGHTS LEGEND Use, duplication, or disclosure by the U.S. Government is
subject to restrictions as set forth in subparagraph (b)(2) of the Technical Data and Computer Software
Commercial Items clause at DFARS252. 211-7015, or in subparagraph (c)(2) of the Commercial
Computer Software-Restricted Rights clause at FAR 52.277-19, as applicable . Microwave Logic, Inc. 285
Mill Road, Chelmsford, MA 01824.
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Pattern Editing Software
TEKTRONIX, MICROWAVE LOGIC PRODUCTS
SOFTWARE LICENSE AGREEMENT
THE ENCLOSED PROGRAM IS FURNISHED SUBJECT TO THE TERMS AND CONDITIONS OF THIS
AGREEMENT, RETENTION OF THE PROGRAM FOR MORE THAN THIRTY DAYS, OPENING THE
SEALED WRAPPER, IF ANY, SURROUNDING THE PROGRAM OR USE OF THE PROGRAM IN ANY
MANNER WILL BE CONSIDERED ACCEPTANCE OF THE AGREEMENT TERMS. IF THESE TERMS
ARE NOT ACCEPTABLE, THE UNUSED PROGRAM AND ANY ACCOMPANYING
DOCUMENTATION SHOULD BE RETURNED PROMPTLY TO MICROWAVE LOGIC, INC. FOR A
FULL REFUND OF THE LICENSE FEE PAID.
DEFINITIONS: "Microwave Logic" means Microwave Logic, Inc. a Delaware corporation, with respect to
a Program acquired by Customer in the United States, with respect to a program acquired by Customer in
Canada.
"Program" means the Microwave Logic software product (executable program and/or data) enclosed with
this Agreement or included within the equipment with which this Agreement is packed.
"Customer" means the person or organization in whose name the Program was ordered.
LICENSE. Customer may:
a. Use the Program under a nontransferable license on a single specified machine.
b. Copy the Program for archival or backup purposes, provided that no
more than one (1) such copy is permitted to exist at any one time.
Each copy of the Program made by Customer must include a reproduction of
any copyright notice or restrictive rights legend appearing in or on the copy of
the Program as received from Microwave Logic.
Customer may not:
a. Transfer the Program to any person or organization outside of Customer
or the corporation of which Customer is a part without the prior written
consent of Microwave Logic.
b. Export or re-export, directly or indirectly, the program, any associated
documentation, or the direct product thereof, to any country to which
such export or re-export is restricted by law or regulation of the United
States or any foreign government having jurisdiction without the
prior authorization, if required, of the Office of Export Administration,
Department of Commerce, Washington, D.C. and the corresponding
agency of such foreign government.
c. For object-code Programs only, reverse compile or disassemble the
Program for any purpose; or
d. Copy the documentation accompanying the Program.
For Programs designed to reside on a single-machine and support one or
more additional machines, either locally or remotely, without permitting the Program to be transferred to
an additional machine for local execution, the additional machines shall be considered within the
definition of "single machine". For programs permitting the Program to be transferred to an additional
machine for local execution, a separate license shall be required for each such machine with which the
Program may be used.
Title to the Program and all copies thereof, but not the media on which the Program or copies may reside
shall be and remain with Microwave Logic.
Customer shall pay when due all property taxes that may now or hereafter be imposed, levied or
assessed with respect to the possession or use of the Program or this license and shall file all reports
required in connection with such taxes.
Any portion of the Program modified by Customer or merged with another program shall remain subject to
these terms and conditions.
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Pattern Editing Software
If the Program is acquired by or for an agency of the U.S. Government, the Program shall be considered
computer software developed at private expense and the license granted herein shall be interpreted as
granting Customer restricted rights in the Program and related documentation as defined in the applicable
acquisition regulation.
THE PROGRAM MAY NOT BE USED, COPIED, MODIFIED, MERGED, OR TRANSFERRED TO
ANOTHER EXCEPT AS EXPRESSLY PERMITTED BY THESE TERMS AND CONDITIONS.
UPON TRANSFER OF ANY COPY, MODIFICATION, OR MERGED PORTION OF THE PROGRAM,
THE LICENSE GRANTED HEREIN IS AUTOMATICALLY TERMINATED.
TERM. The license granted herein is effective upon acceptance by Customer,
and shall remain in effect until terminated as provided herein. The License may be terminated by
Customer at any time upon written notice to Microwave Logic The license may be terminated by
Microwave Logic or any third party from whom Microwave Logic may have obtained a respective licensing
right if Customer fails to comply with any term or condition and such failure is not remedied within thirty
(30) days after notice thereof from Microwave Logic or such third party. Upon termination by either party,
Customer shall return to Microwave Logic, the Program and all associated documentation, together with
all copies in any form.
LIMITED WARRANTY. Microwave Logic warrants that the media on which the Program is furnished and
the encoding of the Program on the media will be free from defects in materials and workmanship for a
period of three (3) months from the date of shipment. If any such medium or encoding proves defective
during the warranty period, Microwave Logic will provide a replacement in exchange for the defective
medium. Except as to the media on which the Program is furnished, the Program is provided "as is"
without warranty of any kind, either express or implied. Microwave Logic does not warrant that the
functions contained in the Program will meet Customer's requirements or that the operation of the
Program will be uninterrupted or error-free.
In order to obtain service under this warranty, Customer must notify Microwave Logic of the defect before
the expiration of the warranty period. If Microwave Logic is unable to provide a replacement that is free
from defects in materials and workmanship within a reasonable time thereafter, Customer may terminate
the license for the Program and return the Program and any associated materials for credit or refund.
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Pattern Editing Software
THIS WARRANTY IS GIVEN BY MICROWAVE LOGIC WITH RESPECT TO THE PROGRAM IN LIEU
OF ANY OTHER WARRANTIES, EXPRESS OR IMPLIED. MICROWAVE LOGIC AND ITS VENDORS
DISCLAIM ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE., MICROWAVE LOGIC'S RESPONSIBILITY TO REPLACE DEFECTIVE MEDIA, OR
REFUND CUSTOMER'S PAYMENT IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO THE
CUSTOMER FOR BREACH OF THIS WARRANTY.
LIMITATION OF LIABILITY, IN NO EVENT SHALL MICROWAVE LOGIC OR OTHERS FROM WHOM
MICROWAVE LOGIC HAS OBTAINED A LICENSING RIGHT BE LIABLE FOR ANY INDIRECT,
SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF OR CONNECTED
WITH CUSTOMER'S POSSESSION OR USE OF THE PROGRAM, EVEN IF MICROWAVE LOGIC OR
SUCH OTHERS HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.
THIRD-PARTY DISCLAIMER. Except as expressly agreed otherwise, third parties
from whom
Microwave Logic may have obtained a licensing right do not warrant the program, do not assume any
liability with respect to its use, and do not undertake to furnish any support or information relating thereto.
GENERAL. This Agreement contains the entire agreement between the parties with respect to the use,
reproduction, and transfer of the Program.
Neither this Agreement nor the license granted herein is assignable or transferable by Customer without
the prior written consent of Microwave Logic.
This Agreement and the license granted herein shall be governed in the United States by the laws of the
State of Delaware.
All questions regarding this Agreement or the license granted herein should be directed in the United
States to the nearest Microwave Logic Sales Office.
H-10
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Theory of Operation
See block diagrams of GB1400 TX and GB1400 RX at end of this section.
GB1400 Generator (TX)
Design Overview
The GB1400 TX is designed to generate a programmable WORD of 16-bits , and
five PRBS of 2n-1 (n=7, 15, 17, 20, 23), at serial data rates of up to 1400 Mb/s.
The unit incorporates a programmable crystal-locked clock source that operates
at this bandwidth, and two programmable pulse output amplifiers, for both Clock
and Data Output.
Very high frequency GaAs, ECL and discrete circuitry is incorporated on
multilayer controlled impedance printed circuit boards. RF shielding and
critically timed coaxial cables provide wideband operation with sub-nanosecond
timing. An embedded CPU controls the programmable clock source, high-speed
data generator hardware, programmable WORD loading, remote RS-232C and
GPIB interfaces, and soft front panel control.
PLL Clock Source PCB
The PLL Clock Source PCB contains the circuitry to generate and distribute the
internal clock signals. The clock source consists of a PLL (Phase Locked Loop)
controlling two VCOs (Voltage Controlled Oscillator). A microprocessor
programs the loop prescale divider ratios.
Data Generator PCB
The Data Generator PCB contains the circuitry required to generate the PRBS
pattern, programmable WORD, clock distribution, error inject circuitry, and
pattern sync generator.
The PRBS data generator utilizes a pattern dependent, n-length shift register
(where of 2n-1 ) with modulo-2 feedback, to generate the desired PRBS pattern.
The shift register operates at 1/2 the system clock frequency. The half-rate data is
split into two phase shifted rails - one is reference, the other is delayed half a
frame. These two rails are available at the rear panel, as "Phase A", and "Phase
B". Internally they are multiplexed together to generate the full rate data output.
The programmable WORD is level shifted from TTL to ECL and loaded into
ECL registers, then multiplexed and clocked out in a serial stream at full-rate.
The 16-bits are loaded at full rate, allowing immediate change to the data pattern.
In PRBS mode, the Pattern Sync circuit detects the start (n, 1, zeros) of the PRBS
pattern. This produces a single bit width pulse once per pattern frame. In WORD
mode, the shift register detects the programmable WORD load pulse, which
occurs once per WORD frame.
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Theory of Operation
The Error Inject circuitry consists of a chain of decade counters, used to generate
a pulse every 10E-n bits (where n=3-7). This pulse generates a single bit error on
the output data streams, providing a known error rate for back-to-back tests.
Data and Clock Output Amplifier PCB
The Data stream generated on the Data Generator PCB is sent to the Output Amp
PCB, relatched into a flip flop, and differentially driven into a monolithic GaAs
pulse amplifier which drives the front panel DATA and DATA invert outputs.
The amplifier provides adjustment, controlled by DACs, of the Data output
Amplitude and baseline Offset. The amplifier will drive 2 Volts peak-to-peak
into a 50 Ohm load, unterminated 4 Volts peak-to-peak, suitable for Fast TTL
and CMOS.
The System Clock signal is sent to the Output Amp PCB, distributed to the Data
latch and also to a discrete GaAs FET pulse amplifier which drives the front
panel CLOCK and CLOCK invert outputs. The amplifier provides adjustment,
controlled by DACs, of the Data output Amplitude and baseline Offset. The
amplifier will drive 2 Volts peak-to-peak into a 50 Ohm load, unterminated 4
Volts peak-to-peak, suitable for Fast TTL and CMOS.
I-2
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Theory of Operation
GB1400 Analyzer (RX)
Design Overview
The GB1400 RX is designed to receive a differential or single-ended
programmable WORD of 16-bits, and five PRBS of 2n-1 (n=7, 15, 17, 20, 23), at
serial data rates of up to 1400 Mb/s, compare it to a locally-generated identical
data stream and perform Bit Error Rate (BER) analysis upon it.
Very high frequency GaAs, ECL and discrete circuitry is incorporated on
multilayer controlled impedance pretend circuit boards. RF shielding and
critically timed coaxial cables provide wideband operation with sub-nanosecond
timing. An embedded CPU controls the high-speed data generator hardware,
programmable WORD loading, error counter calculations, AUTO SEARCH
parameters, remote RS-232C and GPIB interfaces, and soft front panel control.
Input Amplifier PCB
The Input Amp PCB contains the circuitry required to receive differential/ single-
ended Data and Clock, and single-ended Reference Data signals. The signals are
provided with selectable termination voltages, variable threshold level and phase
delay between CLOCK and DATA to accommodate DUT (Device-Under-Test)
skew. Delay and Input Threshold are controlled by the CPU either automatically
in AUTO SEARCH mode, or manually through front panel control.
Data Generator PCB
The Data Generator PCB contains the circuitry required to generate the local
PRBS pattern or programmable WORD for comparison with the received pattern.
The locally-generated pattern is compared bit-by-bit at full rate. The differences
are "Bit Errors" and are counted by the Error Counter PCB.
When the Bit Error Rate (BER) exceeds the SYNC threshold (25% in PRBS,
3.1% in WORD mode, variable with 1 Mbit WORD option), the Data Generator
PCB initiates the synchronization process, by feed-forward technique on
incoming PRBS data, or clock-slip technique on programmable WORD data.
Once synchronization is established BER measurements begin.
The PRBS data generator utilizes a pattern dependent, n-length shift register
(where of 2n-1 ) with modulo-2 feedback, to generate the desired PRBS pattern.
The shift register operates at 1/2 the system clock frequency. The half-rate data is
split into two phase shifted rails - one is reference, the other is delayed half a
frame. These two rails are available at the rear panel, as "Phase A", and "Phase
B". Internally they are multiplexed together to generate the full rate data output.
The programmable WORD is level shifted from TTL to ECL and loaded into
ECL registers, then multiplexed and clocked out in a serial stream at full-rate.
The 16-bits are loaded at full rate, allowing immediate change to the data pattern.
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Theory of Operation
In PRBS mode, the Pattern Sync circuit detects the start (n, 1, zeros) of the PRBS
pattern. This produces a single bit width pulse once per pattern frame. In WORD
mode, the shift register detects the programmable WORD load pulse, which
occurs once per WORD frame.
Error Counter PCB
The Error Counter PCB contains the circuitry to count the Bit Errors detected by
the Data Generator PCB, and also measures the system clock frequency. A Bit
Error Rate (BER) is defined as a ratio of errors/bits, the CPU divides the total
errors by the total bits, and displays the quotient on the front panel LCD as BER.
Total bit errors are also displayed, along with frequency. All counting is done at
full rate, latched and calculated by the CPU.
Common to both GB1400 TX and GB1400 RX
CPU PCB
The CPU PCB contains the CPU, RAM and software PROMs. The 80188
microprocessor handles all inter-board communication, storage and loading of
the programmable 16-bit WORD error counting and frequency calculations,
internal clock PLL control and scale calculations, front panel interface and
remote communication over the RS-232C and GPIB interfaces. Battery-backup
RAM provides storage of ten programmed data patterns, ten programmed clock
frequencies error status, and unit operating status after power loss.
Front Panel PCB
The front panel PCB provides user control of the unit, and contains the key
decoders, LED drivers and 2 x 24 liquid crystal display.
I-4
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0.1uf
EXT CLK
CLOCK/4 OUT
AMPL
50 Ohm
CLK
F/4
CLOCK OUT
F
F
CLOCK SYNTHESIZER
CLK
CLOCK DIVIDER
& DISTRIBUTION
_
F
CLOCK OUT
REAR
PANEL
OFF
PATTERN SYNC
PHASE A
PHASE B
DATA INHIBIT
4:2 MUX
DATA INVERT
AMPL
CLOCK/2
CLK
PRN GEN
SYNC
WORD GEN
CLK
CLK
ERROR
INJECT
DATA OUT
R
Q
D
EXT
CLK
_
DATA
OUT
Q
EXTERNAL
ERROR INJECT
CPU BUS
OFF
FRONT
PANEL
2 x 24 LCD
DISPLAY
CPU BUS
AC INPUT
POWER
SUPPLY
DC OUT
CPU
NON-VOLATILE
RAM
BATTERY
GB1400 Tx
Figure I-1. Block Diagram - GB1400 TX
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Theory of Operation
+
DATA IN
DATA MONITOR
ERROR INHIBIT
Q
_
PROGRAM
DELAY
50ohm
D
-
CLK
Q
50ohm
AC
AC
-2V
DATA INVERT
REAR PANEL
-2V
REF MODE
INTERNAL DATA PATTERN
REF DATA IN
50ohm
+
Q
_
D
PROGRAM
DELAY
Q
CLK
-
REF THRESHOLD
AC
-2V
GND
CLOCK MONITOR
PROGRAMMABLE
ERROR/SYNC
THRESHOLD
SLIP
CLOCK
CLK
CLK
CLOCK
DIST
LOAD
NETWORK
FEED
+
ERRORS
-
50ohm
CLOCK BAR
50ohm
MUX
LOAD
NETWORK
PATTERN SYNC
AC
CLK
SYNC CLK
SYNC SLIP CLK
DATA
CLK
-2V
ERROR
OUT
ERROR
COUNTER
PRN GEN
WORD GEN
ERROR OUT
AC
-2V
DATA THRESHOLD
CPU BUS
FRONT
PANEL
2 x 24 LCD
DISPLAY
REAR PANEL
NON - VOLATILE
RAM
cpu
AC
INPUT
POWER
SUPPLY
DC OUT
BATTERY
GB1400 Rx
Figure I-2. Block Diagram - GB1400 RX
I-6
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Glossary/ Index
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Glossary
Address
A number specifying a particular user device attachment point... The location of
a terminal, a peripheral device, a node, or any other unit or component in a
network...A set of numbers than uniquely identifies something - a location in
computer memory, a packet of data traveling through a network.
Analog-to-Digital Converter
A device that converts an analog signal, that is, a signal in the form of a
continuously variable voltage or current, to a digital signal, in the form of bits.
Attenuation
A decrease in magnitude of current, voltage, or power of a signal in transmission
between points.
Attenuator
An electronic transducer, either fixed or adjustable, that reduces the amplitude of
a wave without causing significant distortion.
Bandwidth
The difference between the limiting frequencies of a continuous frequency
spectrum. The range of frequencies handled by a device or system.
BER
An acronym for Bit Error Ratio (or Rate). The principal measure of quality of a
digital transmission system. BER is defined as:
BER = Number of Errors/Total Number of Bits
BER is usually expressed as negative exponent. For example, a BER of 10-7
means that 1 bit out of 107 bits is in error.
BER Floor
A limiting of the bit-error-ratio (BER) in a digital fiber optic system as a function
of received power due to the presence of signal degradation mechanisms or
noise.
Binary
A numbering system that allows only two values, zero and one, (0 and 1). Binary
is the way most computers store information., in combination of ones and zeros.
Voltage on. Voltage off. See also: Bit.
Bit
A binary digit, the smallest element of information in binary system. A 1 or 0 of
binary data.
Bit Error
An incorrect bit. Also known as a coding violation.
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Glossary
Bit Rate
The number of bits of data transmitted over a phone line per second.
Byte
A unit of 8 bits.
Channel
A communications path or the signal sent over a channel. Through multiplexing
several channels, voice channels can be transmitted over an optical channel.
Clock
1. An electronic component that emits consistent signals that paces a computer’s
operations. 2. An oscillator-generated signal that provides a timing reference for
a transmission link. A clock provides signals used in a transmission system to
control the timing of certain functions, such as the duration of signal elements or
the sampling rate. It also generates periodic, accurately spaced signals used for
such purposes as timing, regulation of the operations of a processor, or
generation of interrupts. A clock has two functions: to generate periodic signals
for synchronization on a transmission facility, and to provide a time base for the
sampling of signal elements. In computers, a clock synchronizes certain
procedures, such as communication with other devices.
Error Detection
Checking for errors in data transmission. A calculation is made on the data being
sent and the results are sent along with it. The receiving station then performs the
same calculation and compares its results with those sent. ...Code in which each
data signal conforms to specific rules of construction so that departures from this
construction in the received signals can be automatically detected. Any data
detected as being in error is either deleted from the data delivered to the
destination, with or without an indication that such deletion has taken place, or
delivered to the destination together with an indication that is has been detected
as being in error.
Error Rate
The ratio of the number of data units in error to the total number of data units.
ES
An acronym for Errored Second. A second with at least one error.
GPIB
A physical layer interface standard for the interconnection of equipment.
Line
The portion of a transmission line between two multiplexers.
LOF
An acronym for Loss of Frame.
LOS
An acronym for Loss of Signal.
glossary-2
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Glossary
Multi-Channel Cable
An optical cable having more than one fiber.
Noise
Unwanted signals that combine with and hence distort the signal intended for
transmission and reception.
Residual error rate
The error rate remaining after attempts at correction are made.
RS-232C
A physical layer interface standard for the interconnection of equipment.
Rx, Receiver
An abbreviation for Receiver
A detector and electronic circuitry to change optical signals to electrical signals.
Tx, Transmitter
An abbreviation for Transmitter
A driver and source used to change electrical signals to optical signals.
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Glossary
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Index
Index
-A-
Appendices
BERT Primer/ Technical Articles, B-1
Analyzer Functions, 3-19
Analyzer Error Messages, 3-45
Cleaning Instructions, G-1
Customer Acceptance Test, E-1
Default Settings, F-1
Audio (Beeper) Function, 3-45
AUTO SEARCH,
"Non-PRBS" Patterns, 3-21
PRBS Patterns, 3-20
Pattern Editing Software, H-1
Remote Commands, C-1
Specifications, A-1
Automatic Setup Func. (SYNC), 3-19
CLEAR Control, 3-45
Theory of Operation, I-1
Using GPIB, RS-232, D-1
Clearing Results, Starting Tests, 3-33
Clock, Data, Ref Data Inputs, 3-23
Applications, 2-38
Display Mode: Totalize, Window or
Test, 3-33
Fibre Channel Link Testing Parallel and
High-Speed Serial, 2-47
Error Detection Set-up, 3-29
Error History Indicators, 3-44
GB700/ GB1400 Optical Component
Test, 2-46
How to DISABLE Automatic Pattern
Resynchonization, 3-21
Method for Very Fast Automatic RX
Synchronization and Eye Width
Measurement, 2-38
Input Data Delay, 3-24
Input Decision Threshold, 3-26
Input Termination, 3-25
QPSK BER Testing using PRBS Data
for 2-Channel I & Q, 2-49
Testing QPSK Modems, I & Q, 2-48
Logically Inverting Input Data, 3-26
Monitor Outputs, 3-28
-B-
Printing Results (Reports), 3-37
BERT Basics - GB1400, 2-2
Burst Mode Option, 2-26
Relationship between AUTO SEARCH
and DISABLE, 3-21
Result Definitions, 3-42
Burst Mode Usage, 2-27
Selecting Reference Data Mode, 3-27
Single-Ended or Differential Op, 3-27
Star & Stop Measurements, 3-46
Synch (LOCK) Threshold, 3-22
Test Process Setup, 3-35
Specifications for Burst Mode, 2-27
Totalize Process Setup, 3-33
Viewing Results, 3-36
Window Process Setup, 3-34
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Index
Nominal Generator Clock, Data
Waveforms showing Amplitude,
Baseline Offset and Vtop, 3-13
-C-
Controls, Indicators, and Connectors, 2-4
Controls & Indicators, 2-18
Analyzer ERROR DETECTION, 2-25
Analyzer Error History, 2-24
Analyzer INPUT, 2-23
Nominal Generator NRZ Data and
Clock Output Waveforms, 2-3
Seven-stage PRBS generator, B-6
TEST Measurement Process, 3-32
Three-stage PRBS generator, B-5
TOTALIZE Measurement Process, 3-30
WINDOW Measurements Process, 3-31
Analyzer SYNC Controls, 2-25
Func (Soft) Keys (F1, F2, F3, F4), 2-21
Generator ERROR INJECT, 2-22
GPIB Controls, 2-19
Functional Overview, 2-1
Functions common to TX and RX, 3-1
AC Power, 3-1
Pattern Controls, Function Keys, 2-20
Power Switches, 2-18
LCD Viewing Angle, 3-1
Locking the Front Panel, 3-2
Recalling Default Setup, 3-2
Reset to Factory Default, 2-18
Unit Cooling , 2-18
Unit Mounting , 2-18
Selecting 115 VAC or 230 VAC
operation, 3-1
View Angle and Panel Lock Keys, 2-18
Turning Instrument Power ON/OFF, 3-1
-D-
Display Formats, 2-6
-G-
Generator Functions, 3-10
Amplitude and Baseline Offset, 3-14
Clock Source and Frequency, 3-10
Clock Source, 3-10
-F-
Figures
Analyzer (RX) Front & Rear Panels, 2-5
Analyzer Clock and Data Input
Equivalent Circuits, 3-22
Data and Clock Outputs, 3-12
Error INJECT Input, 3-18
Error Injection, 3-17
Analyzer Display, 2-7
Block Diagram - GB1400 RX, I-6
Block Diagram - GB1400 TX, I-5
Example of BERT Application, 2-2
Four-stage PRBS generator, B-5
Generator Front & Rear Panels, 2-4
External Clock Input, 3-10
Logically Inverting Output Data
(D-INV), 3-15
Pattern SYNC (PYNC) and CLOCK/4
Outputs, 3-16
Generator Clock and Data Output
Equivalent Circuits, 3-17
Recalling a Frequency, 3-11
Saving a Frequency, 3-11
Generator Display, 2-6
Selection an Error Inject Mode, 3-17
Index-2
GB1400 User Manual
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Index
Single-Ended or Differential Operation,
3-16
Utility Option (OPTION), 3-82
Utility Version (VER), 3-83
Step Size and Frequency, 3-10
Window Interval in Bits (BITS), 3-72
Getting Started, 1-1
Window Interval in Hrs:Min:Sec
(SECOND), 3-73
Window Mode (MODE), 3-71
Window Reports (REPORT), 3-74
Word Edit (EDIT), 3-56
-I-
Initial Self-Check Procedure, 1-7
Word Fill (FILL), 3-58
-M-
Menus, 3-48
Word Length (LENGTH), 3-57
Word Order (ORDER), 3-59
Using the Menu System, 3-48
General Rules, 3-51
Word Synchronization Threshold
(SYNC), 3-60
Menu and Function "Pages", 3-48
Menu Overview, 3-1
-O-
Outputs & Inputs, 2-9
Analyzer INPUT, 2-13
Menu Summaries, 3-52
Auto, 3-62
Buffer, 3-61
Analyzer MONITOR, 2-14
GPIB, 3-81
Analyzer Rear Panel, 2-15
Menu Function Definitions, 3-55
RS-232 Baud Rate (BAUD), 3-75
RS-232 Data Bits (SIZE), 3-77
RS-232 Echo (ECHO), 3-80
RS-232 End-of-Line Char.(EOL), 3-78
RS-232 Parity (PARITY), 3-76
RS-232 Xon/Xoff (XON/XOFF), 3-79
Test Length (LENGTH), 3-63
Test Mode (MODE), 3-64
Test Print (PRINT), 3-68
Test Reports (REPORT), 3-65
Test Squelch (SQUEL), 3-67
Test Threshold (THRES), 3-66
Test View Current (VIEW-CUR), 3-70
Test View Previous (VIEW-PRE), 3-69
Time Option (DATE), 3-84
Time Option (TIME), 3-85
Changing the Line Fuse, 2-12, 2-15
Connectors, Terminations, Levels, 2-16
Generator CLOCK, 2-10
Generator OUTPUT (Set-up), 2-11
Generator OUTPUT, 2-9
Generator Rear Panel, 2-12
-P-
PECL option for GB1400 Tx, 2-29
GB1400 User Manual
Index-3
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Index
-S-
-W-
Selecting an Active Pattern, 3-3
Word Patterns, 3-5
Basics, 3-5
Selecting (Recalling) a Saved Word
Pattern, 3-4
Selecting PRBS Patterns, 3-3
Selecting the Current Word Pattern, 3-3
Creating Word Patterns using front
panel controls, 3-5
Creating Word Patterns using menus,
3-7
Selecting a Pattern, 3-2
Pattern Definitions, 3-2
PRBS Patterns , 3-2
Word Patterns, 3-3
Creating Word Patterns using remote
control, 3-8
Recalling Word Patterns, 3-9
Saving Word Patterns, 3-9
-T-
Tables
Actions taken by Analyzer when
Synchronization is Lost, 3-20
Analyzer Inputs & Outputs, 2-17
Analyzer Menu System Overview, 3-53
Data Inhibit Logic, 3-18
Generator Inputs & Outputs, 2-16
Generator Menu System Overview, 3-54
How F2, F3 set Input Set-up, 3-24
How to Tell which Display Mode is
Active, 3-37
Input Terminations for CLOCK, DATA,
and REF DATA, 3-25
Input Threshold Range as a Function of
Termination, 3-26
Menu Descriptions, 3-52
Output Setup Rules vs. Termination
Impedance, 3-14
PRBS (2N-1) Test Patterns, 3-3
PRBS Polynomials and Shift Register
feedback taps for PB200, B-4
PRBS Polynomials, Shift Register
feedback taps, GB700/ GB1400, B-4
Synchronization Threshold, 3-22
Tutorial, 2-30
Index-4
GB1400 User Manual
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