Multi Tech Systems Network Card MT2834MR6 User Manual

MultiModem

MT2834MR6

User Guide

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Contents

Chapter 1 - Introduction ..................................................................................... 7

1.1 Introduction ............................................................................................. 8

1.2 Manual Organization............................................................................... 8

1.3 Description ............................................................................................. 9

1.4 FCC Regulations for Telephone Line Interconnection........................... 10

1.4.1 FCC Fax Update ................................................................................. 10

1.5 Canadian Limitations Notice ................................................................. 11

1.6 Technical Specifications ....................................................................... 12

1.7 Power Supply ....................................................................................... 14

1.8 Modem LED Indicators ......................................................................... 15

1.9 Busy Switch ......................................................................................... 15

1.10 MT2834MR6 Installation Notes ............................................................. 16

1.11 Safety Warnings ................................................................................... 16

Chapter 2 - Dialing and Answering ................................................................. 17

2.1 Introduction ........................................................................................... 18

2.2 Dial-UpAutomaticAnswering ............................................................... 18

2.3 Dial-Up Handshaking Details ................................................................ 18

2.4 Call Termination .................................................................................... 19

Chapter 3 - AT Commands .............................................................................. 20

3.1 Working with AT Commands ................................................................ 21

3.1.1 ModesofOperation ............................................................................ 21

3.2.2 CommandStructure ............................................................................ 22

3.3.3 CommandEditing ............................................................................... 22

3.2 Dialing Commands............................................................................... 26

3.3 Dial Modifier Commands ...................................................................... 27

3.4 Phone Number Memory Commands.................................................... 30

3.5 Configuration Storage and Recall Commands ..................................... 32

3.6 Modem Response (Result Code) Commands ..................................... 34

3.7 Online Connection Commands ............................................................ 36

3.8 V.34 Commands................................................................................... 40

3.9 RS-232 Interface Commands .............................................................. 41

3.10 Error Correction and Data Compression Commands.......................... 43

3.11 Speed Conversion Commands ............................................................ 45

3.12 Immediate Action Commands .............................................................. 47

3.12 Flow Control Commands ..................................................................... 49

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3.13 Escape Sequences .............................................................................. 52

3.14 Remote Configuration Commands....................................................... 53

3.15 Line Probe Commands ........................................................................ 54

3.16 Diagnostic Commands......................................................................... 55

Chapter 4 - S-Registers .................................................................................... 56

4.1 Introduction ........................................................................................... 57

4.2 S-Registers .......................................................................................... 57

4.3 Reading and Assigning S-Register Values ........................................... 63

4.3.1 Examples of Assigning Values ........................................................... 63

4.3.2 Examples of Reading Values.............................................................. 63

4.4 AT Commands Affecting S-Registers................................................... 64

Chapter 5 - Error Correction, Data Compression & Speed Conversion..... 65

5.1 Introduction ........................................................................................... 66

5.2 How V.42 Detects and Corrects Errors ................................................ 67

5.3 Data Compression ............................................................................... 68

5.4 MNP Classes........................................................................................ 68

5.5 V.42 Mode Select Command (#L)......................................................... 69

5.5.1 #L0Command ..................................................................................... 69

5.5.1.1 Originate Mode ................................................................................ 69

5.5.1.2 Answer Mode ................................................................................... 69

5.5.2 #L1Command ..................................................................................... 69

5.5.3 #L2Command .................................................................................... 69

5.5.4 #L3Command ..................................................................................... 69

5.6 Modes of Operation .............................................................................. 70

5.6.1 Non-ErrorCorrectionMode(&E0)........................................................ 70

5.6.2 ReliableMode(&E2) ........................................................................... 70

5.6.3 AutoreliableMode(&E1) ..................................................................... 70

5.7 Flow Control ......................................................................................... 71

5.8 Modem-Initiated Flow Control ............................................................... 72

5.8.1 XON/XOFFFlowControl(&E5) ........................................................... 72

5.8.2 HardwareFlowControl(&E4) .............................................................. 72

5.9 Pacing (&E13) ...................................................................................... 73

5.9.1 XON/XOFFPass-Through(&E7) ........................................................ 73

5.9.2 Non-ErrorCorrectionModeFlowControl(&E10and&E11)................. 73

5.9.3 Hewlett Packard ENQ/ACK Pacing (&E9)........................................... 73

5.10 Compression, Error Correction, Flow Control,

and Pacing Commands........................................................................ 74

5.10.1 V.42 Error Correction Modes .............................................................. 74

5.10.2 Modem-InitiatedFlowControl ............................................................. 74

5.10.3 XON/XOFFPass-Through .................................................................. 74

5.10.4 Hewlett Packard ENQ/ACK Pacing..................................................... 74

5.10.5 Non-ErrorCorrectionModeFlowControl ............................................. 74

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5.10.6 Pacing(Computer-InitiatedFlowControl)............................................ 74

5.10.7 DataCompression .............................................................................. 74

5.11 Result Codes........................................................................................ 75

5.11.1 MNPErrorCorrection .......................................................................... 75

5.11.2 LAP-MErrorCorrection ....................................................................... 75

5.11.3 DataCompression .............................................................................. 75

5.12 Speed Conversion ................................................................................ 75

5.12.1 Baud Adjust ($BA) .............................................................................. 76

5.12.2 Modem Baud Rate ($MB).................................................................... 76

5.12.3 Serial Port Baud Rate ($SB) ............................................................... 77

5.13 Related Commands ............................................................................. 78

5.13.1 AutoreliableBuffering($A) .................................................................. 78

5.13.2 Maximum Block Size (&BS) ............................................................... 78

5.13.3 AutoreliableFallbackCharacter($F) ................................................... 78

5.13.4 RetransmitCount($R) ........................................................................ 79

5.13.5 V.42 Error Correction at 300 bps ($E) ................................................. 79

5.14 Summary.............................................................................................. 79

Chapter 6 - Testing & Troubleshooting.......................................................... 80

6.1 Introduction ........................................................................................... 81

6.2 Local Analog Loopback Test (V.54 Loop 3) ........................................... 82

6.2.1 TestProcedure ................................................................................... 82

6.3 Remote Digital Loopback Test (V.54 Loop 2)........................................ 83

6.3.1 TestProcedure ................................................................................... 83

6.4 Local Digital Loopback Test (V.54 Loop 2)............................................ 84

6.4.1 TestProcedure ................................................................................... 84

Chapter 7 - Warranty & Service ....................................................................... 85

7.1 Multi-Tech Systems, Inc. Warranty & Repairs Policies......................... 86

7.1.1 Warranty ............................................................................................. 86

7.1.2 U.S. and Canadian Customers............................................................ 86

7.1.3 International Customers (outside U.S.A. and Canada) ........................ 87

7.1.4 InternationalDistributors ..................................................................... 87

7.2 Repairs ................................................................................................. 88

7.2.1 Repair Procedures for U.S. and Canadian Customers ........................ 88

7.2.2 RepairProceduresforInternationalCustomers................................... 88

7.2.3 RepairProceduresforInternationalDistributors .................................. 89

7.2.4 ReplacementParts ............................................................................. 89

7.3 Technical Support ................................................................................. 89

7.4 Internet Site .......................................................................................... 89

Appendices........................................................................................................ 90

AppendixA ..................................................................................................... 91

ASCIIConversionChart................................................................................... 91

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Appendix B .................................................................................................... 92

Dial Pulses ...................................................................................................... 92

ToneDialFrequencies ..................................................................................... 93

Appendix C .................................................................................................... 94

ResultCodeSummary..................................................................................... 94

Appendix D .................................................................................................... 96

S-RegisterSummary ....................................................................................... 96

Appendix E .................................................................................................... 98

AT Command Summary .................................................................................. 98

Appendix F................................................................................................... 106

RS-232CInterfaceSpecifications .................................................................. 106

Functional Description of the RS-232C Signals ............................................. 107

Transmitted Data (TD) — Pin 2 ...................................................................... 107

Received Data (RD) — Pin 3.......................................................................... 107

RequestTo Send (RTS) — Pin 4 .................................................................... 107

ClearTo Send (CTS) — Pin 5 ......................................................................... 107

Data Set Ready (DSR) — Pin 6 ..................................................................... 107

Signal Ground (SG) — Pin 7 .......................................................................... 107

Carrier Detect (CD) — Pin 8 ........................................................................... 107

Test Voltage (+V) — Pin 9 .............................................................................. 108

High Speed (HS) — Pin 12............................................................................. 108

Transmit Clock (TC) — Pin 15 ........................................................................ 108

Receive Clock (RC) — Pin 17 ........................................................................ 108

DataTerminal Ready (DTR) — Pin 20 ............................................................ 108

Ring Indicator (RI) — Pin 22 .......................................................................... 109

External Transmit Clock (XTC) — Pin 24........................................................ 109

Terminal Busy (OOS) — Pin 25...................................................................... 109

Appendix G .................................................................................................. 110

CableandConnectorDiagrams ..................................................................... 110

APPENDIX H ................................................................................................111

Introduction to MultiTech Escape Methods ................................................... 111

How to Select an Escape Method.................................................................. 112

Escape Method 1:+++AT<CR> ..................................................................... 112

Escape Method 2:<BREAK>AT<CR> ........................................................... 112

S-Registers and Escape Sequence ............................................................... 113

Aborting an Escape Sequence ...................................................................... 113

APPENDIX I ................................................................................................. 114

IntroductiontoRemoteConfiguration ............................................................. 114

BasicProcedure ............................................................................................ 114

Setup 114

ChangingthePasswords ............................................................................... 115

ChangingtheRemoteEscapeCharacter ....................................................... 115

Index ................................................................................................................. 116

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Chapter 1 - Introduction

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Chapter 1 - Introduction

1.1 Introduction

Welcome to the world of data communications. You have acquired one of the finest rack-mount intelligent

modems available, the MT2834MR6, from Multi-Tech Systems. This owner’s manual will help you install,

configure, test, and use your modem.

Your MT2834MR6 is designed to operate as an enhanced ITU-T V.34 dial-up modem. As such, it includes

the advanced features of Multi-Tech standalone modems, such as the popular MultiModemZDXb.

This manual documents all of the MT2834MR6’s features and capabilities, such as autodial, autoanswer,

auto-fallback, number linking, option switches, phone number memory, call progress detection, and more.

The next section will show you how to use this manual. The contents of each chapter are described, so you

will know where to turn for specific information.

1.2 Manual Organization

Chapter 1 Introduction and Description

This chapter describes the MT2834MR6 and its LED indicators, gives its technical specifications, and

provides a guide to the organization of the manual.

Chapter 2 Dialing and Answering

This chapter describes answer mode operation in detail, including handshaking procedures between two

modems and an autoanswer application. Various methods of call termination are also described.

Chapter 3 Command Mode Operation

This chapter provides an introduction to MT2834MR6 command mode fundamentals, followed by a detailed

explanation of each AT command, providing examples where applicable.

Chapter 4 S-Registers

This chapter describes the MT2834MR6’s S-registers, which are used to store various modem options. Each

S-register is defined and explained.

Chapter 5 Error Correction, Data Compression and Speed Conversion

This chapter provides detailed information about some of the advanced features of the MT2834MR6, namely,

V.42 error correction, data compression, speed conversion, and other features that improve throughput.

Chapter 6 Testing the MT2834MR6

This chapter describes loopback testing for the MT2834MR6.

Chapter 7- Warranty, Service, and Technical Support

This chapter provides the terms of the MT2834MR6’s warranty, instructions for obtaining factory service, and

information about Multi-Tech’s BBS and technical support. Information on upgrading the MT2834MR6’s

firmware is also provided.

Appendices

This chapter includes sections pertaining to ASCII/HEX/Decimal Conversion Chart, Dial Pulses and Tone

Dial Frequencies, Result Code Summary, S-Register Summary, AT Command Summary, RS-232 Interface

Specifications, Cable and Connector Diagrams, Escape Methods, and Remote Configuration.

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Chapter 1 - Introduction

1.3 Description

Each MT2834MR6 card contains six integrated 33,600 bps MultiModems. Each modem on the MT2834MR6

card can be configured independently of the others via the MultiModemManager controller card (Model

MR4800 or MR4800E), which can support and control up to 16 MultiModem cards per rack. Refer to your

MultiModemManager Owner’s Manual for more information about the rack and its components.

Perhaps the most significant extras incorporated in the MT2834MR6 are its V.42 error correction and V.42bis

data compression features. With error correction and data compression, transmission errors are eliminated

while increasing the modem’s throughput by a ratio of up to 4:1, for an effective overall transmission rate

approaching 115,200 bps.

The MT2834MR6 offers interactive automatic dialing capability, as well as command mode option

configuration. Two dial command strings, of up to 60 digits each, can be stored in each modem’s nonvolatile

memory. The modem supports both pulse and tone dialing, and can recognize dial tones and busy signals

for reliable call-progress detection.

The MT2834MR6 is registered by the FCC for direct connection to the public telephone networks. No Data

Access Arrangements (DAAs) are required.

The MT2834MR6 is fully compatible with the standard AT command set, and is therefore compatible with all

popular communications software packages.

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Chapter 1 - Introduction

1.4 FCC Regulations for Telephone Line Interconnection

1. No repairs are to be made by you. Repairs are to be made only by Multi-Tech Systems or its licensees.

Unauthorized repairs void registration and warranty. Contact Multi-Tech Systems, Inc. for details of how

to have repairs made.

2. When trouble is experienced, you must disconnect your modem from the telephone company’s jack to

determine the cause of the trouble, and reconnect your modem only when the trouble is corrected.

3. The modem cannot be connected to pay telephones or party lines.

4. If requested by the telephone company, you must notify them of the following before the MT2834MR6 is

installed:

a. The particular phone line (phone number) to which the connection is to be made.

b. The FCC Registration Number: AU7USA-30805-MM-E

c. The Ringer Equivalence: 0.3B

d. Modems can only be connected to the phone lines through standard modular jacks. The

Uniform Service Order Code (U.S.O.C.) for the standard modular jack which connect the modem

to the phone lines are: RJ-11C or RJ-11W (single line)

e. The manufacturer’s name and model number: Multi-Tech Systems - Model MT2834MR6

5. If the telephone company notifies you that your device is causing harm, unplug it. The telephone

company may disconnect your service if necessary and also may change its facilities, equipment,

operations or procedures which may affect operation of your equipment. Where practical, the telephone

company must promptly inform you in writing of the temporary disconnect or change in service, give you

the opportunity to make changes allowing uninterrupted service, and inform you of your rights to bring a

complaint to the FCC.

1.4.1 FCC Fax Update

The Telephone Consumer Protection Act of 1991 makes it unlawful for any person to use a computer or other

electronic device to send any message via a telephone fax machine unless such message clearly contains in

a margin at the top or bottom of each page or the first page of the transmission, the date and time it is sent

and an identification of the business or other entity, or other individual sending the message and the

telephone number of the sending machine or such business, other entity, or individual.

See your fax software manual for setup details.

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Chapter 1 - Introduction

1.5 Canadian Limitations Notice

Notice: The ringer equivalence number (REN) assigned to each terminal device provides an indication of the

maximum number of terminals allowed to be connected to a telephone interface. The termination of a

interface may consist of any combination of devices subject only to the requirement that the sum of the ringer

equivalence numbers of all the devices does not exceed 5.

Notice: The Industry Canada label identifies certificated equipment. This certification means that the

equipment meets certain telecommunications network protective, operational and safety requirements.

Industry Canada does not guarantee the equipment will operate to the user’s satisfaction.

Before installing this equipment, users should ensure that it is permissible to be connected to the facilities of

the local telecommunications company. The equipment must also be installed using an acceptable method of

connection. The customer should be aware that compliance with the above conditions may not prevent

degradation of service in some situations.

Repairs to certified equipment should be made by an authorized Canadian maintenance facility designated

by the supplier. Any repairs or alterations made by the user to this equipment, or equipment malfunctions,

may give the telecommunications company cause to request the user to disconnect the equipment.

Users should ensure for their own protection that the electrical ground connections of the power utility,

telephone lines and internal metallic water pipe system, if present, are connected together. This precaution

may be particularly important in rural areas.

Caution: Users should not attempt to make such connections themselves, but should contact the appropriate

electric inspection authority, or electrician, as appropriate.

Industry Canada Certification Number:

Ringer Equivalence Number (REN): 0.2

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Chapter 1 - Introduction

1.6 Technical Specifications

Model Number

MT2834MR6

Data Rates (Modem)

Six independent modems (Modem A, B, C, D, E, F), each operating at 33,600,

31,200, 28,800, 26,400, 24,000, 21,600, 19,200, 16,800, 14,400, 12,000, 9600,

4800, 2400, 1200, or 0-300 bps

Data Rates (Fax)

14,400, 9600, 4800, and 2400 bps

Data Format (Modem) Serial, binary, asynchronous at all data rates

Configuration

Each of the card’s six modems is independently configurable

Compatibility (Modem) ITU-T V.42bis, V.42, V.34, AT&T V.32terbo, ITU-T V.32bis, V.32, V.25bis, V.21,

V.22bis, V.22, V.23, V.17, Bell 212A* and 103/113*

Compatibility (Fax)

Error Correction

ITU-T Group 3, T.4, T.30, V.21, V.27ter, V.29, V.17, and EIA TR29.2

ITU-T V.42 (MNP® Classes 3 and 4, and LAP-M)

Data Compression

Speed Conversion

ITU-T V.42bis (4:1 throughput) or MNP 5 (2:1 throughput)

Serial port data rates adjustable to 300, 1200, 2400, 4800,9600, 19,200, 38,400,

57,600, and 115,200 bps

FlowControl

XON/XOFF, CTS/RTS, ENQ/ACK

Mode of Operation

Half or full duplex over dial-up lines; automatic or manual dialing, automatic or

manual answer

Intelligent Features

Fully AT command compatible; autodial; redial; repeat dial*; dial linking*; pulse or

tone dial; dial pauses; call status display; auto-parity and data rate selection;

keyboard-controlled modem options; nonvolatile memory; on-screen displays of

modem parameters, stored telephone numbers, and help menus; and remote

configuration.

AT Commands

100% compatible with standard AT command set

60 characters

Command Buffer

Automatic Dialing

ModemModulations

Standard AT command asynchronous dialing

FSK at 300 bps, PSK at 1200 bps, QAM at 2400, 4800, and 9600 bps (non-trellis),

QAM with trellis-coded modulation (TCM) at 9600, 12,000, 14,400, 16,800, 19,200,

21,600, 24,000, 26,400, 28,800, 31,200, and 33,600 bps

FaxModulations

V.21 CH2 FSK at 300 bps

V.27ter DPSK at 4800 and 2400 bps

V.29 QAM at 9600 and 7200 bps

V.17TCM at 14400, 12000, 9600, and 7200 bps

1600, 1646, 1680, 1800, 1829, 1867, 1920,

1959, 2000 Hz

Carrier Frequencies

ITU-T V.34

Carrier Frequencies:

AT&T V.32 terbo/

ITU-T V.32bis/V.32

Carrier Frequencies:

V.22bis/V.22 or

1800 Hz

Transmit originate:

Transmit answer:

Receive originate:

Receive answer:

1200 Hz

2400 Hz

1200 Hz

Bell 212A Standard

(2400 & 1200 bps)

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Chapter 1 - Introduction

Carrier Frequencies:

Bell 103/113

Transmit originate:

1270 Hz mark

1070 Hz space

(300 bps)

Receive originate:

Transmit answer:

Receive answer:

Transmit originate:

2225 Hz mark

2025 Hz space

2225 Hz mark

2025 Hz space

1270 Hz mark

1070 Hz space

Carrier Frequencies:

V.21

980 Hz mark

1180 Hz space

Receive originate:

Transmit answer:

Receive answer:

Transmit originate:

1650 Hz mark

1850 Hz space

1650 Hz mark

1850 Hz space

980 Hz mark

1180 Hz space

Carrier Frequencies:

V.23

390 Hz mark

450 Hz space

Receive originate:

Transmit answer:

1300 Hz mark

2100 Hz space

1300 Hz mark

2100 Hz space

Receive answer:

390Hz mark

450Hz space

FaxModulations

V.21Ch2 FSK at 300 bps

V.27ter DPSK at 4800 and 2400 bps

V.29 QAM at 9600 and 7200 bps

V.17 TCM at 14400, 12000, 9600, and 7200 bps

V.21 CH2 (half duplex)

Fax Carrier

Frequencies

1650 Hz mark, 1850 Hz space for transmit originate

1650 Hz mark, 1850 Hz space for transmit answer

V.27ter: 1800 Hz Originate/Answer

V.29 QAM: 1700 Hz Originate/Answer

V.17 TCM: 1800 Hz Originate/Answer

Transmit Level

Frequency Stability

Receiver Sensitivity

AGC Dynamic

Range

-13 dBm

+0.01%

-43 dBm under worst case conditions

43 dB

Serial Interface

Diagnostics

EIA RS-232C

Power-on self-test; ITU-T V.54 local analog loop, local digital loop, remote digital

loop.

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Chapter 1 - Introduction

Firmware Upgrades

Indicators

Via flash PROM technology on Multi-Tech’s BBS

LEDs for Transmit Data, Receive Data, Carrier Detect, Speed, and Off Hook/Out-

Of-Service

Controls

Toggle switches for busy-out

Environmental

Temperature range: 0°–50° C (32°–120° F)

Humidity range: 20–90% (noncondensing)

Power

5 VDC at 0.95 A

Requirements

Power Consumption

Dimensions,

card modem

Weight

±16 VDC at 0.1 A

Approximately 6 watts

.9 × 11 × 15 in. (2.2 × 28 × 37 cm) H × W × D

2.5 lb. (1.1Kg)

Limited Warranty

Fuses

Two years

F1 (+5V), F2 (-16V), F3 (+16V)

1.7 Power Supply

DC voltages are supplied to all modems in the CC4800A rack through one or two PS4800A power supplies,

designed for conventional 115 or 230 VAC connection. The power supply is a universal input switching

power supply.

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Chapter 1 - Introduction

1.8 Modem LED Indicators

The MT2834MR6 has five LED indicators per modem:

TD Transmit Data. This LED blinks when data is being transmitted, on for a space, off for a mark. The

state of this LED matches that of the TD circuit on Pin 2 of the RS-232C interface.

RD Receive Data. This LED blinks when data is received, on for a space, off for a mark. The state of

this LED matches that of the RD circuit on Pin 3 of the RS-232C interface.

CD Carrier On. This LED lights when a valid carrier tone has been detected.

Speed Speed. This LED blinks at different rates to indicate the speed of the data connection:

Data Rate (bps)

LED State

12000 or less

Off

14400 or 16800

19200 or 21600

24000 or 26400

28800 or more

Slow blink rate

Medium blink rate

Fast blink rate

OH/OOS Off Hook/Out of Service. This LED lights when the modem is off hook, which occurs when the

modem is dialing, online, or answering a call. The LED flashes when the modem is in the busy-

out or out-of-service state.

Note: The PS4800 modem rack power supply has one LED that indicates the presence of all supply voltages.

1.9 Busy Switch

The MT2834MR6 has six two-position Busy switches on the front panel. Each switch can be used to create a

“busy-out” (OOS) condition for one of the six on-board modems (i.e., modem A, B, C, D, E, or F).

To place a modem in the Busy condition, move the appropriate Busy switch to the right. The selected modem

goes off-hook, its OH/OOS LED begins to flash, and incoming calls to this modem get a busy signal. If you

suspect a problem with a particular modem, you can use the Busy switch to have an optional device (such as

a “hunt group”) that looks for a non-busy line to perform a rollover to the next available modem while you

check the status of the Busy modem.

Note: The MultiModemManager can perform the same function using software.

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Chapter 1 - Introduction

1.10 MT2834MR6 Installation Notes

All installation must be done by a qualified service person.

The installation instructions in your MultiModemManager Owner’s Manual include information about the use

of blanking plates to cover empty slots in the card frame. Be sure to follow those instructions.

Warning: Interconnection directly, or by way of other apparatus, of ports marked “SAFETY WARNING see

instructions for use” with ports marked or not so marked may produce hazardous conditions on the network.

Advice should be obtained from a competent engineer before such a connection is made.

This product is intended to be hard wired to the network. The final connection to the network is the

responsibility of the public telecommunications network operator or a person authorized by that operator.

Any other apparatus, including cable and wiring, connected between the MT2834MR6K modem and the

point of connection to any speechband circuit shall comply with the following:

1. The overall characteristics of this apparatus shall be such as to introduce no material effect upon the

electrical conditions presented to one another by the modem and he speechband circuit.

2. The apparatus shall comprise only

a. apparatus approved for the purpose of connection between the modem and a speechband

circuit; and

b. cable and wiring complying with a code of practice for the installation of equipment covered by

this part of BS 6328 or such other requirements as may be applicable.

Note: Such apparatus may have been approved subject to limitations in its use.

1.11 Safety Warnings

• Never install telephone wiring during a lightning storm.

• Never install telephone jacks in wet locations unless the jacks are specifically designed for wet locations.

• Never touch uninsulated telephone wires or terminals unless the telephone line has been disconnected at

the network interface.

• Use caution when installing or modifying telephone lines.

• Avoid using a telephone (other than a cordless type) during an electrical storm. There may be a remote

risk of electrical shock from lightning.

• Do not use the telephone to report a gas leak in the vicinity of the leak

• Ports that are connected to other apparatus are defined as SELV. To ensure conformity to EN 41003,

ensure that these ports are only connected to the same type on the other apparatus.

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Chapter 2 - Dialing and Answering

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Chapter 2 - Dialing and Answering

2.1 Introduction

This chapter describes the dialing and answering capabilities of the MT2834MR6 modems, which are

standard ITU-T V.34 full duplex dial-up modems.

2.2 Dial-Up Automatic Answering

The MT2834MR6 can answer calls automatically. The MT2834MR6 is in originate mode in its idle state.

When it detects an incoming call, it automatically switches to answer mode. You can program the modem to

answer a call after a certain number of rings by using register S0 (see Chapter 4).

2.3 Dial-Up Handshaking Details

This section briefly explains what happens between two modems in a normal call. We are assuming that

there are MT2834MR6s at both the originating and at the answering end of the telephone line. (If other

brands of modems are used with our modems, they will still communicate, but each manufacturer tends to

use slightly different delay timings and sequences, and many of the brands vary in their indicator

designations.)

Before V.34 negotiation takes place, remote and local modems transfer their functional capabilities using

modulated calling and answering tones. First, the Calling Menu (CM), a data sequence using V.21 low-band

modulation (a handshaking technique originally developed for 300 bps modems), is sent from the originating

V.34 modem to the answering V.34 modem. This describes the range of functional capabilities the originating

modem supports. The answering V.34 modem responds to the CM with a Joint Menu, or JM (using V.21 high-

band modulation), indicating the common capabilities of the modem at each end.

Once this is done, a probing signal is passed between the modems to identify impairments in the telephone

channel. After receiving the results of the probing signal, the modem receivers and transmitters will start with

the lowest speed and move up until reaching the highest speed at which they can exchange data. All this

occurs in about five seconds.

Note: In order for the called modem to be able to answer the call, it must have a high DTR (Data Terminal

Ready) signal on pin 20 of the RS-232C interface. This signal comes from the computer or terminal to which

the modem is connected.

Note: If you are using reliable or auto-reliable mode, some additional handshaking takes place. This is

explained in Chapter 5, in the “Auto-Reliable Mode” section.

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Chapter 2 - Dialing and Answering

2.4 Call Termination

There are several methods by which you can terminate a call, or simply stated, hang up:

1. Command Mode Control. It is possible to enter command mode while remaining online by entering an

escape sequence (+++AT<CR> in most cases). From command mode, you can return to the online state

by typing ATO, or you can terminate the call by using the H command. Typing ATH will hang up the line

(bring it on-hook). So the command to hang up a call is three plus signs followed by ATH.

2. DTR Control. If DTR (Data Terminal Ready) is turned off for 50 milliseconds or more, a disconnect will

occur. This is probably the most common method used by computer systems at the autoanswer end of

the line to cause the calling modem to disconnect after logoff procedures.

3. Loss of Carrier. Once a data connection has been established, the modem will disconnect if a loss of

carrier occurs for 700 milliseconds (0.7 seconds) or longer. This time can be configured with register S10

for any time from 0 to 25.5 seconds (in 100 mSec increments). Note that one cause of carrier loss would

be if one of the modems were to disconnect normally. S10 works for speeds of 2400 bps or below. S10

has no effect at connections above 2400 bps.

4. Abort Timer. Answer Mode: When OH (Off Hook) comes on, the called modem starts a 45 second timer

and waits for a carrier signal from the originating modem. If a carrier is not detected within this period, the

modem disconnects (hangs up) and is ready for another call. Originate Mode: The abort timer functions

the same as in the answer mode, except that the timer begins after the modem has completed dialing,

instead of when it first goes off hook. It is possible to change this 45-second wait period to any other

value from 1 second up to 254 seconds by reconfiguring register S7 (see Chapter 4).

5. Inactivity Timer. Causes the modem to disconnect if no data is being transmitted or received for a

certain period of time. The timer is reset anytime a character passes through the serial port in either a

send or receive direction. This function is controlled by register S30. The inactivity timer can be disabled

by setting S30 to 0, which is the factory default setting, or set to time out after number of minutes selected

by register S30.

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Chapter 3 - AT Commands

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Chapter 3 - AT Commands

3.1 Working with AT Commands

The MT2834MR6’s modems are controlled by instructions called AT commands, so called because the

attention characters AT precede each command or command string (sequence of commands). You can send

commands to the modem from your keyboard while in terminal mode, or you can use communications

software to issue these commands automatically.

The MT2834MR6 is in command mode when it is not dialing or online. When it is in command mode, you

have access to a complete communications system that allows you to use several features, including the

basic AT command set described in this chapter. Using the basic AT command set, you can enter phone

numbers for automatic dialing, configure modem options, and monitor telephone activity. In addition, you can

command your modem to perform advanced features such as error correction, data compression, speed

conversion, and more.

This chapter explains command mode, and shows you how to use each of the MT2834MR6’s AT commands.

MT2834MR6 commands and responses are compatible with all systems and with all data communications

software using the AT command set.

For easy reference, the MT2834MR6 has a help command that provides you with short, on-screen

descriptions of the modem commands. The help command is explained later in this chapter.

3.1.1 Modes of Operation

The MT2834MR6 operates in two basic functional modes: command mode and online mode. (There is also

an in-between state, wait-for-carrier, in which the modem is out of command mode but not yet online.) When

you power up the modem, it is in command mode, and is ready to accept and respond to commands from

your keyboard or software.

An MT2834MR6 modem enters online mode after it dials, connects with another modem, and detects a valid

carrier signal. If it does not detect a carrier signal within the time frame controlled by register S7, the modem

abandons the call and re-enters command mode.

You can make the modem enter online mode without dialing by typing either the D command or the A

command.

The modem exits online mode if the carrier signal is lost or intentionally dropped. When this happens, the

modem hangs up and re-enters command mode.

By sending certain “escape” characters to the modem while online, you can make it enter command mode

without losing the carrier signal.

For autoanswer-only applications, you can disable a modem’s ability to recognize AT commands by using

the %DC1 command. When you do this, the MT2834MR6 ignores all commands, and functions as a non-

intelligent modem. The %DC1 command and other MT2834MR6 commands are explained later in this

chapter.

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Chapter 3 - AT Commands

3.2.2 Command Structure

You can control a wide variety of modem operations and options when the modem is in command mode. AT

commands tell the modem to dial a number, to answer a call, to operate at a certain speed, to use a certain

compression technique, and many other functions. AT commands consist of one or two letters, which may be

preceded by an ampersand (&), a dollar character ($), a pound character (#), a percent character (%), or a

greater-than character (>). The Q command, for example, determines whether the modem returns result

codes, while the &Q command selects which AT command set the modem uses.

A parameter after a command (0, 1, 2, etc.) tells the modem which option to use. If you do not specify a

parameter, the modem assumes the 0 (zero) option. E, for example, is the same as E0. You can issue several

commands on a single line (a command string) as long as the line does not exceed 60 characters. Note that

though Q1 is one command, it counts as two characters in the command line.

Each command has a valid range of parameters; for instance, &W can have only 0 or 1 as a parameter. Valid

commands generate an OK result code. A few generate an additional response, such as a list of parameters.

An invalid command, such as &W3, which has a parameter outside the valid range, generates an ERROR

result code. Most commands have a default parameter, one that is enabled when the modem is turned on or

reset with the ATZ or AT&F command. Factory defaults are stored in read-only memory (ROM), and cannot

be changed. User-defined defaults can be stored in nonvolatile random-access memory (NVRAM), and can

be changed or deleted at will.

3.3.3 Command Editing

Always begin a command with the letters AT. You may type the command in upper case or lower case, but

not both. The AT command is not executed until you press the ENTER key. Use the BACKSPACE key to

erase the previous command character; it will not erase the AT characters once they are typed. If your

keyboard has no BACKSPACE key, use CTRL+H. You can change the character recognized by the modem

as BACKSPACE to any other ASCII character by changing register S5.

To cancel an entire command that has been typed but not yet executed, press CTRL+X. This also clears the

command buffer. The effect is the same as backspacing the command, only quicker.

The MT2834MR6 stores characters entered in a command in the modem’s command buffer until they are

executed by pressing ENTER. The command buffer’s capacity is 60 characters. The attention characters (AT)

do not count in the 60 allowed command characters. You may use spaces for increased readability when

typing a command; they are neither stored in the command buffer nor counted in the 60 allowed characters.

Hyphens, parentheses, etc., are not allowed.

If you exceed the 60-character limit or type invalid characters, the command buffer is automatically erased

and an ERROR message is displayed. You must then retype the command within the 60-character limit,

using only the allowed characters.

The commands in this chapter are organized by function. A brief summary follows.

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Chapter 3 - AT Commands

Table 3-1. AT Commands by Function

Topic:

Command:

Description:

DialingAction

Dial

Continuous redial

On-hook/off-hook

Dial Modifiers

Pulse dialing

Tone dialing

Wait for new dial tone

Reverse originate/answer mode

Dialing pause

Continuous redial

;

Return to command mode after dialing

Flash on-hook

Quiet answer

Call card tone detect

Phone Number

Memory

D...N

N...N

Store a phone number

Dial a stored number

Number linking

List stored telephone numbers

Configuration

Storage & Recall

Store configuration

Load default configuration

Reset modem

Modem Responses

(Result Codes)

Echo command mode characters

Result codes: enable/disable

Result codes: Multi-Tech or standard

Result codes: verbose/terse

Result codes and call progress

Answerback

OnlineConnection

Auto speed detection

Answer tone

%DC

&CD

>DT

&RD

Command mode control

Cleardown at disconnect

DTMF detection

Fallback modes when online

Guard tones

Busy-Out After Disconnect

Pulse dial ratios

Square wave ring detect

Calling tones

Trellis-coded modulation

Long space disconnect

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Chapter 3 - AT Commands

Table 3-1. AT Commands by Function (con't)

Topic:

Command:

Description:

V.34 Controls

&RA

Echo canceler frequency offset comp.

Asymmetric bit rate

V.32terbo handshake

RS-232 Interface

Controls

Carrier Detect control

Data Terminal Ready control

Clear to Send control

&RF

&SF

Data Set Ready control

CTS/RTS interaction control

DSR/CD interaction control

Error Correction &

Data Compression

&E0

&E1

&E2

&E14

&E15

Non-error correction mode

Autoreliable mode

Reliable mode

Data compression disabled

Data compression enabled

V.42 error correction modes

V.42 error correction at 300 bps

Autoreliable buffering

Autoreliable fallback character enable

Retransmit count

Speed Controls

$BA

$MB

$SB

Baud adjust

Modem baud rate

Serial port baud rate

Immediate Action

&RN

&RR

Repeat last command

Inquire product code

List current operating parameters

List S-register values

List current operating parameters

List online diagnostics

Rate renegotiation

Retrain

FlowControl

&BS

$EB

&E3

&E4

&E5

&E6

&E7

&E8

&E9

Maximum reliable block size

Asynchronous word length (10/11-bit)

Flow control disabled

Hardware flow control

XON/XOFF flow control

XON/XOFF no pass-through

XON/XOFF pass-through

Hewlett Packard ENQ/ACK pacing off

Hewlett Packard ENQ/ACK pacing on

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Chapter 3 - AT Commands

Table 3-1. AT Commands by Function (con't)

Topic:

Command:

Description:

&E10

&E11

&E12

&E13

Non-error correction mode flow control off

Non-error correction mode flow control on

Pacing off

Pacing on

Number of XOFF characters sent

Escape

+++AT<CR>

Default in-band escape sequence

Sequences

Alternate out-of-band escape sequence

Escape sequence selection

Force answer mode

Go back online

Remote

%%%AT<CR> Remote configuration escape sequence

Configuration

Change login password

Change setup password

Line Probes

%DP

%DF

&RP

L10

L11

Read line probe data

Format line probe data

Immediate line probe

Display signal strength

Display signal to noise ratio

Display noise strength

Diagnostics

Respond to remote digital loopback signal

Loopback test modes

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Chapter 3 - AT Commands

3.2 Dialing Commands

Dialing commands are used to dial and to hang up.

Dial

s = phone number

Default: none

The letter D in a command causes the modem to dial the telephone number immediately

following it. For example, if you type ATD5551212<CR>, the modem dials the number 555-

1212.

The MT2834MR6 supports several dialing methods. With the D command, you can specify

either pulse (ATDP) or tone (ATDT) dialing. You can also modify the dialing command with

several characters that are explained in “Dial Modifier Commands” in this chapter.

The MT2834MR6 lets you select either smart (wait-for-dial-tone) dialing or blind dialing.

With smart dialing, the modem waits for and detects dial tones and busy signals. With blind

dialing, the modem works with timed pauses (determined by the value of register S6), not

dial tone and busy signal detection. See the X command for more information on blind and

smart dialing.

ContinuousRedial

If you select smart dialing through the X3 or X4 command, the A: command lets you

continuously redial a busy number until your call is answered. (North American units have a

maximum of 10 redials; this command is not available on U.K. or International models.)

Use this command only if you have reached a busy number after executing a normal dial

command. Type A: (you need not type AT, nor do you need to press ENTER), and the

modem redials the number. If you again reach a busy signal, the modem continues to redial

until it gets through. You can stop the modem from redialing by pressing any key.

To save a step when redialing a phone number, enter a colon (:) at the end of the phone

number. The result is the same as if you had entered A:

Note: This command has been largely superseded by software-based continuous redial features.

On-Hook/Off-Hook

n = 0 or 1

Default: none

You can make the modem go on-hook (hang up) or go off-hook with the H command.

H0 (or H) hangs up the modem

H1 brings the line off-hook, just as if you had picked up the telephone handset.

It is not necessary to use the H1 command to bring the line off-hook when using the D

command. The modem automatically goes off-hook when you press ENTER at the end of

the dial command.

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Chapter 3 - AT Commands

3.3 Dial Modifier Commands

The dial string can include the digits 0 through 9, the pound sign (#), the asterisk (*), and the letters A, B, C,

or D. The latter are used by some PBXs; the exact function will depend on the PBX manufacturer’s feature set

and implementation. There are also several command characters, called “dial modifiers,” that can be

included within a dialing command after the letter D. Their functions include pulse or tone dialing, pauses in

the dial sequence, automatic redials if a number is busy, and reverting to command mode or switching to

answer mode after dialing.

P, T

Pulse or Tone Dialing

Default: P

The MT2834MR6’s modems can dial numbers by using pulse dialing, tone dialing, or a

combination of both methods. Pulse dialing, used by rotary-dial telephones, uses the timed

opening and closing of a relay to encode the numbers. Tone dialing, used by push-button

(touch-tone) telephones, uses dual tone multifrequency (DTMF) dialing.

P selects pulse dialing.

T selects tone dialing.

Insert P or T in the dialing command just before the digits you want to pulse- or tone-dial.

For example, to pulse-dial the number 555-1212, type ATDP5551212 and press ENTER.

To tone-dial the same number, type ATDT5551212 and press ENTER. If neither pulse nor

tone dialing is specified in the dial command, the modem uses whatever method was used

last.

Immediately after the modem has been turned on or reset, it uses pulse dialing, even if you

do not include P in your dial command.

As an example of combining pulse and tone dialing, assume you are calling out of a PBX

(switchboard) system where a 9 has to be pulse-dialed, then the rest of the number has to

be tone-dialed after pausing for a second dial tone. To dial this example, type

ATDP9,T5551212 and press ENTER. (The comma causes a pause.)

Wait for New Dial Tone

Inserting W into the dialing command causes the modem to wait for another dial tone before

it resumes dialing. (It is not necessary to enter W at the beginning of the dialing command.)

Because the modem must be able to detect the dial tone for this command to work, you also

must select wait-for-dial-tone dialing with the X2 or X4 command.

Reverse Originate/Answer Mode

n = 0 or 1

Default: R0

The R command lets you reverse the modem’s mode of operation from originate to answer,

or from answer to originate; for example, if you need the modem to answer the phone but

then go into originate mode.

R (with no number) at the end of the dialing string reverses in originate mode.

R0 disables mode reversing.

R1 enables mode reversing when R is added to the dial string.

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Chapter 3 - AT Commands

Dialing Pause

Enter a comma in the dialing string to make the modem pause while dialing. This pause

lasts two seconds (North American models) or four seconds (U.K. and International models)

for each comma entered. You can force longer pauses by entering multiple commas, or you

can change the length of the pause caused by a comma by setting register S8 to any value

from 0 through 255 seconds (North American models), 4 through 7 seconds (U.K. models)

or 4 through 255 seconds (International models).

Each comma in a dialing command counts as one of the 60 allowed characters.

ContinuousRedial

Enter a colon (:) as the last character of a dialing command, to cause the modem to

continuously redial the number, if it detects a busy signal, until the call is answered. North

American models are limited to 10 redials. You must select smart dialing (X3 or X4) for this

to work. (Not available in U.K. or International models.)

Note: This command has largely been superseded by software-based continuous redial features.

;

Return to Command Mode After Dialing

Enter a semicolon (;) as the last character of a dialing command to cause the modem to

return to command mode immediately after executing the command instead of waiting for a

carrier signal and going online.

For example, type ATDT5551212; to tone-dial the number and immediately go back into

command mode. The semicolon is useful when modem data transfer is not desired, as in

voice communications, or in applications using touch tones as a data entry method, such as

bank-by-phone.

Flash On-Hook

Some switchboard systems react to a momentary on-hook condition. Insert an exclamation

mark into the dialing command to cause the modem to “flash” on-hook for half a second,

just as if you had pressed the switch hook on a telephone set for half a second. (With U.K.

models, the exclamation mark causes the modem to flash on-hook for 90 milliseconds.)

For example, to flash on-hook to transfer to extension 5678 after dialing the number 555-

1234, type ATDT5551234,,!5678. The commas cause a 4-second pause.

Quiet Answer

Use the @ command to access a system that does not provide a dial tone. The @ command

causes the modem to wait before processing the next character in the dialing string. The

wait is for one or more rings back followed by five seconds of silence.

For example, ATDT5551212@6313550 causes the modem to dial the first number (555-

1212), then wait for the time specified in register S7 for at least one ringback and five

seconds of silence. If the modem detects a busy signal, it hangs up and generates a BUSY

result code. If it does not detect five seconds of silence, it hangs up and generates a NO

ANSWER result code. If it does detect five seconds of silence, it dials the second number

(631-3550).

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Chapter 3 - AT Commands

Call Card Tone Detect

Use the $ command to dial services that require you to enter your call card number after a

tone. A $ character in the dialing string causes the modem to pause and wait for an AT&T

call card “bong” or a 1600 Hz tone (prevalent in the U.K.). When the modem detects the

tone, it processes the rest of the dialing string. If it does not detect a tone within the time set

by register S7 (a 45-second default), the modem aborts with a NO CARRIER message.

Pressing any key also aborts the $ command.

In the following example, the $ command is placed between an access/phone number and

the caller’s credit card number:

ATDT1028806127853500$123456789

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Chapter 3 - AT Commands

3.4 Phone Number Memory Commands

The modem can store up to two telephone numbers in nonvolatile memory. You can store the numbers with

the DsNd command, dial them with the Nd command, link them so that one will be automatically dialed after

the other with the NdNe command, or list them with the L command.

DsNd

Store a Phone Number

s = phone number

d = 0 or 1

Default: none

You can store a telephone number command string of up to 60 characters in the modem’s

phone number memory. You can store two of these 60-character strings using the DsNd

command. The memory locations are labeled N0 and N1.

Store a command line by typing it as you would any other command, appending the

appropriate Nd memory location.

For example, the tone-dialed number 1-612-555-1212 is stored at memory location N0 by

typing ATDT16125551212N0 and pressing ENTER. The number is not dialed with this

store command.

After storing a number, check to see that it has been stored correctly by typing ATL and

pressing ENTER.

When you store a phone number, you store the entire command string, so you can

effectively create a macro for each number. For example, if you know a particular number

needs to have extended result codes, detect busy or dial tone, error correction, XON/XOFF

flow control, pacing, and data compression enabled, the command to store the entire

command string at location N0 is ATX4&E1&E5&E13&E15DT16125551212N0.

Dial a Stored Number

d = 0 or 1

Default: none

You can automatically dial a telephone number that is stored in the modem’s number

memory by typing ATNn, where n = 0 or 1. For example, you can dial a number stored at N0

by typing ATN0 in terminal mode and pressing ENTER.

Warning: Do not include the letter D in this command, or the stored number will be erased.

NdNe

NumberLinking

d = 0 or 1

e = 1 or 0

Default: none

Number linking allows the modem to dial a second stored number if the first stored number

is busy. (See the DsNd command.) This command is useful when a computer can be

accessed through more than one phone number. However, it cannot be used with blind

dialing, since busy signals would not be detected.

To link the number in memory location N0 to the number in N1, type ATN0N1 and press

ENTER. You can cycle back and forth between two numbers by linking them several times

in one command: ATN0N1N0N1N0N1<CR>. The only limit on the number of times the

modem can cycle between two numbers is the 60-character maximum allowed in a

command line.

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Chapter 3 - AT Commands

List Stored Telephone Numbers

Use the L command to display dialing commands stored in the modem’s nonvolatile

memory. Typing ATL<CR> displays the stored N numbers in the following format:

T14082345678

P9,T14089876543

All digits and command letters are displayed. The N number is shown first, followed by the

complete dialing command and telephone number as originally entered.

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Chapter 3 - AT Commands

3.5 Configuration Storage and Recall Commands

The MT2834MR6 stores parameters in two places. It stores factory default parameters in read-only memory

(ROM), and customized parameters in nonvolatile random access memory (NVRAM). You cannot change the

default parameters in ROM; however, you can change parameters in temporary memory and then store them

in NVRAM as custom settings. You can then recall the custom settings as if they were factory default settings.

&Wn

Store Configuration

n = 0 or 1

Default: &W1

The &W command stores current AT commands and S-register values in nonvolatile

memory, so you won’t lose your custom settings when you turn off the modem or reset it.

&W0 (or &W) stores all current AT command and S-register values in nonvolatile random

access memory (NVRAM) and configures the modem so that it reads your custom settings

in NVRAM when the modem is turned on or when it is reset with the Z command. (The &F

reset command will continue to read the factory default settings in ROM unless you store

the &F9 command.)

&W1 erases your custom settings in NVRAM when the modem is turned off or reset,

causing the modem to read the factory default settings in ROM when it is subsequently

turned on or reset.

For further information on how the &W command interacts with the reset commands, see

Table 3-2.

&Fn

LoadDefaultConfiguration

n = 0, 8, or 9

Default: &F8

The MT2834MR6 modems store factory default AT command settings and S-register values

in read-only memory (ROM); they store your custom AT command and S-register values in

nonvolatile random access memory (NVRAM).

The &F0 (or &F) command resets the modem to the factory default values stored in ROM or

to your custom values stored in NVRAM, depending on whether you last stored an &F8 or

an &F9 command.

When &F8 is stored and an &F command is issued, the modem reads the factory default

settings stored in ROM.

When &F9 is stored and an &F command is issued, the &W setting determines whether the

modem reads settings stored in NVRAM or ROM. If the modem is set to &W0, it reads your

custom settings stored in NVRAM. If the modem is set to &W1, it erases your stored settings

(including the &F9 command) and reads the factory default settings stored in ROM. Many

communications programs issue the &F command automatically—the &F9 command allows

you to select your own defaults.

Note that for either an &F8 or an &F9 command to be effective after a reset it must be stored

using the &W0 command.

Table 3-2 summarizes how the &F and Z reset commands interact with the &W command;

note that the &F reset command operates differently from the Z reset command:

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Chapter 3 - AT Commands

Table 3-2. Where the Modem Reads Configuration Parameters

Power-On

and ATZ

Previous Command

AT&F

AT&W1 (default)

AT&W0

AT&F8&W0

AT&F9&W0

ROM

NVRAM

ROM

NVRAM

Reset Modem

The Z command resets the modem to its default configuration and clears the command

buffer. The result is the same as turning the modem off and on. When you type ATZ, the

state of the &W command determines where the default values originate. &W0 defaults

come from the customized configuration in NVRAM, and &W1 defaults come from the

factory default configuration in ROM. Because Z clears the command buffer, it must be the

last command in a command string; normally it is issued by itself: ATZ.

Note that the Z reset command operates differently from the &F reset command. See Table

3-2.

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Chapter 3 - AT Commands

3.6 Modem Response (Result Code) Commands

The MT2834MR6’s modems can give responses to commands. The most common one is OK, but the

modems also can alert you or your software to dial tones, busy signals, connection speeds, and whether the

connection is made with error correction or compression enabled. These responses are called result codes,

and they can be terse or verbose, Multi-Tech or standard, basic or extended.

Echo Command Mode Characters

n = 0 or 1

Default: E1

Normally, when you type commands on the keyboard, the modem echoes the characters

back to the computer or terminal, which displays them on the monitor. Use the E command

to turn this feature off and on.

E0 disables the echo.

E1 enables the echo.

Result Codes Enable/Disable

n = 0, 1, or 2

Default: Q0

You can use the Q command to enable or disable result codes for applications such as

computer-controlled autodialing. You can also use it to disable responses and echo in

answer mode while leaving originate mode still intelligent; this is called the no response

answer mode of operation.

Q0 (or Q) enables result codes.

Q1 disables result codes for applications such as computer-controlled auto-dialing.

Q2 enables the no response answer mode, which leaves originate mode intelligent

while turning off answer mode responses and echo.

&Qn

Result Codes (Multi-Tech or Standard AT)

n = 0 or 1

Default: &Q0

The MT2834MR6 gives you a choice between Multi-Tech result codes and standard AT

command set responses. Multi-Tech result codes give you more information, but some

datacomm programs may not be able to use them, in which case, select the standard result

codes.

&Q0 selects Multi-Tech responses with RELIABLE, LAPM, and COMPRESSED modifiers.

With &Q0, the verbose result code for 14,400 bps is CONNECT 14400 LAPM

COMPRESSED.

&Q1 selects AT responses with no RELIABLE, LAPM, or COMPRESSED modifiers. With

&Q1, the verbose result code for 14,400 bps is CONNECT 14400.

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Chapter 1 - Introduction

Result Codes (Verbose/Terse)

n = 0 or 1

Default: V1

The V command controls whether the modem’s result codes display as verbal (“verbose”) or

digital (“terse”) messages. For example, if no carrier signal is detected after dialing, the

result can be displayed either as NO CARRIER, or as the digit 3.

V0 (or V) displays the modem’s result codes as digits.

V1 displays result codes as words.

Result Codes and Call Progress Selection

n = 0–4

Default: X0

The X command selects which result codes the modem provides in command mode and

whether the modem uses “smart dialing” or “blind dialing”. When it smart dials, the modem

listens for dial tones and busy signals and responds to them. When it blind dials, the

modem ignores the signals and relies on timing instead.

X0 causes the modem to blind dial. Instead of looking for a dial tone, it pauses for the time

set in register S6 and then dials regardless. Once a connection has been made, it sends

the Bell 103 basic code CONNECT to the terminal. It ignores any busy signals.

X1 causes the modem to blind dial, but in addition to the basic CONNECT code it provides

extended codes consisting of the word CONNECT and the speed of the connection:

CONNECT 2400, CONNECT 4800, CONNECT 9600, CONNECT 14400, CONNECT 19200,

CONNECT 28800, and so forth. In this mode, the modem does not recognize or respond to

dial tones or busy signals.

X2 causes the modem to wait for a dial tone before dialing. If it does not detect a dial tone

within the time set by S6, the modem sends a NO DIALTONE result code to the terminal. In

this mode, the modem provides extended result codes, but does not respond to busy

signals.

X3 causes the modem to blind dial, but also it looks for a busy signal, and if it detects one, it

sends a BUSY result code to the terminal. In this mode, the modem provides extended

result codes, but it does not respond to dial tones.

X4 causes the modem to look for a dial tone and a busy signal, and respond with NO

DIALTONE or BUSY, as appropriate. It also provides extended result codes. It is the most

useful setting for most datacomm programs.

&An

Answerback

n = 0 or 1

Default: &A0

The &A command controls the MT2834MR6’s answerback feature. Answerbacks are used

in some online realty applications and elsewhere as a security measure. The &A command

enables a modem to return a message to an identification request from another computer.

The default identification is MESSAGE NOT PROGRAMMED.

&A0 disables the answerback feature.

&A1 enables the modem to return a message to an inquiry.

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Chapter 3 - AT Commands

3.7 Online Connection Commands

The following commands control the conditions of the online connection.

#An

Auto Speed Detection

n = 0–3

Default: #A0

An MT2834MR6 modem can operate as a 33,600 bps, 28,800 bps, 19,200 bps, 14,400 bps,

9600 bps, 4800 bps, 2400 bps, or 300 bps modem. Use the #A command to select the

speed that the modem uses for initial handshaking and subsequent speed selection. The

#A command does not control the originating bps rate of the modem (that is done by the

modem baud rate command $MB), but only the answer mode starting speed.

#A0 causes the modem to start at maximum speed, with fallback to 31,200 to 28,800 to

26,400 to 24,000 to 21,600 to 19,200 to 16,800 to 14,400 to 12,000 to 9600 to 4800 to 2400

to 1200 to 300 bps.

#A1 causes the modem to operate at maximum speed only.

#A2 causes the modem to start at maximum speed, with decremental fallback to 4800 bps.

#A3 causes the modem to start at 2400 bps in V.22bis mode, with fallback to 1200 to 300

bps.

Answer Tone

n = 0 or 1

Default: B0

The B command selects the frequency the modem uses for its answer tone. (The answer

tone is the tone a modem receiving a call transmits to the modem that called it, thus

initiating the handshake between the two modems.) At higher speeds (2400 to 33,600 bps)

there is no conflict, because all protocols use the Bell frequency of 2225 Hz. However, the

ITU-T specification for V.22 has an answer tone frequency of 2100 Hz. This command is

available only in International models.

B0 enables ITU-T frequencies including V.21 (300 bps) and V.23 (1200/75 bps).

B1 enables Bell frequencies including Bell 103 (300 bps).

%DCn

AT Command Control

n = 0 or 1

Default: %DC0

The %DC command allows you to disable the modem’s ability to respond to AT commands.

It can be used with autoanswer applications in which no call origination is required, with

some UNIX applications, and with other applications that require you to disable the

modem’s command mode.

%DC0 enables command mode.

%DC1 disables command mode.

Note: If you save %DC1 as part of your default configuration, you can re-enable command mode by typing

AT%DC0 and pressing ENTER in the first ten seconds after you power up the modem.

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Chapter 3 - AT Commands

&CDn

>DTn

#Fn

Cleardown at Disconnect

n = 0 or 1

Default: &CD0

In the V.32, V.32bis, and V.34 protocols, a cleardown is sent by one of the modems to

signal the other modem that it is going to hang up. A cleardown is rate renegotiation in

which the modem that is hanging up tells the other modem that it has no speeds that it can

connect at. It is designed to help the remote modem detect a hangup. However, it does take

a second or two to send the cleardown. If you find this delay unacceptable, you can disable

cleardown by using the &CD command.

&CD0 enables cleardown at disconnect.

&CD1 disables cleardown at disconnect.

DTMF Detection

n = 0 or 1

Default: >DT0

Normally, when it goes off-hook, a fax modem ignores tones from the other end of the

connection unless they are fax or modem handshake tones, in which case it responds in

kind. The >DT1 command causes the modem to report DTMF (touch-tone) tones and fax

calling tones to software for further processing. A typical use would be for a program that

routes calls to specific communications applications depending on the type of call or upon a

DTMF tone added to a dialing string.

>DT0 disables DTMF detection.

>DT1 enables DTMF detection when the modem goes off-hook.

Fallback Modes

n = 0, 1, or 2

Default: #F2

The #F command controls whether the modem will fall back to a lower speed because of an

unacceptable error rate. If line conditions deteriorate, the modem has the ability to fall back

from its original speed to the next lower speed when operating in V.34, V.32terbo, V.32bis,

or V.32 mode. If the error rate becomes too great, the modem performs a retrain at the next

lower speed. If, after the retrain, the error rate is still too high, the modem performs a retrain

at the next lower speed, down to 4800 bps.

If the modem returns online at the original speed after the first retrain, the modem starts a

counter and a timer. If three retrains occur within a two-minute period, the modem falls back

to 4800 bps.

The fallback and fall-forward speeds for the modem are 33.6K, 31.2K, 28.8K, 26.4K, 24.0K,

21.6K, 19.2K, 16.8K, 14.4K, 12K, 9.6K, and 4.8K bps.

#F0 (or #F) disables fallback when online.

#F1 lets the modem fall back from the starting speed to a low speed of 4800 bps in 2400

bps decrements.

#F2 lets the modem fall back when line conditions deteriorate, but also lets it fall forward in

2400 bps increments if line conditions improve.

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Chapter 3 - AT Commands

&Gn

Guard Tones

n = 0, 1, or 2

Default: &G0 (models outside U.K.)

&G2 (U.K. models only)

The &G command is used to control the presence or absence of guard tones from the

transmitter when in answer mode at either 1200 or 2400 bps. Guard tones are used in

Europe and other areas to allow the modem to function in the telephone systems. Guard

tones are not used in the United States. U.K. models are locked at &G2 (1800 Hz guard

tone).

&G0 disables ITU-T guard tones.

&G1 enables ITU-T 550 Hz guard tone.

&G2 enables ITU-T 1800 Hz guard tone.

*Hn

Busy-Out After Disconnect

n = 0 or 1

Default: *H0

The *H1 command causes the MT2834MR6 to remain out of service and return a busy

signal until configuration from the MultiModemManager dedicated management console

has finished. If no configuration option is set on the dedicated management console, the

MT2834MR remains out of service for ten seconds after disconnect. Register S94 controls

the length of the out-of-service, or busy-out, time (see Chapter 4).

*H0 disables busy-out after disconnect.

*H1 enables busy-out after disconnect.

&Pn

Set Pulse-Dial Ratios

n = 0 or 1

Default: &P0 (Models outside U.K.)

&P1 (U.K. models only)

The &P command sets the time ratios between the open (break) and closed (make) states

of dialing pulses. U.K. models are locked to &P1 (67:33 ratio). See Appendix B for more dial

pulse information.

&P0 sets a pulse dial ratio of 60 ms break to 40 ms make.

&P1 sets a pulse dial ratio of 67 ms break to 33 ms make.

&RDn

Square Wave Ring Detect

n = 0 or 1

Default: &RD0 (U.K. and International models)

&RD1 (North American models)

The ringback sound that you hear when you dial a number is generated at the local

telephone office or PBX. Normally, it is a sine wave analog tone. However, some PBXs

generate square wave rings that can go undetected by normal ring detection circuits,

resulting in a failure to make a connection. To enable your modem to detect square wave

rings, use the &RD1 command.

&RD0 enables sine wave ring detection only.

&RD1 enables sine wave and square wave ring detection.

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Chapter 3 - AT Commands

$Tn

#Tn

CallingTone

n = 0 or 1

Default: $T1

The $T command enables or disables the modem’s calling tone, which is required by some

European countries to identify the caller as a modem.

$T0 enables the calling tone.

$T1 disables the calling tone.

Trellis-CodedModulation

n = 0 or 1

Default: #T1

The #T command enables or disables trellis-coded modulation (TCM) on the modem. There

is usually no need to disable TCM, except for an unusual line condition called impulse

noise.

#T0 disables TCM.

#T1 enables TCM.

Long Space Disconnect

n = 0 or 1

Default: Y0

When two modems are connected in reliable mode, a link disconnect request packet is sent

to request a disconnect. In non-error correction mode, there is no “polite” way to request a

disconnect. As a result, some “garbage” may be received when a hang-up command is

issued.

Y0 disables the modem’s use of the break signal.

Y1 enables the modem’s use of the break signal, which shuts off the modem’s receiver and

disconnects (both modems must have Y1 enabled).

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Chapter 3 - AT Commands

3.8 V.34 Commands

The following commands apply only in V.34 mode.

%Fn

Echo Canceler Frequency Offset Compensation

n = 0 or 1

Default: %F0

The %F command enables and disables echo canceler frequency offset compensation

which, when enabled, can decrease modem performance.

%F0 disables echo canceler frequency offset compensation.

%F1 enables echo canceler frequency offset compensation.

&RAn

Asymmetric Bit Rate

n = 0 or 1

Default: &RA0

The &RA command enables or disables asymmetric bit rate operation in V.34 mode. The

asymmetric bit rate feature lets the modem transmit at one rate while receiving at a different

rate.

&RA0 enables asymmetric bit rate operation.

&RA1 disables asymmetric bit rate operation.

#Vn

V.32terbo Handshake

n = 0 or 1

Default: #V1

Some V.32/V.32bis modems have problems handshaking when the MT2834MR6 includes

V.32terbo mode (19,200 bps) in its handshake. The bits that are used in the rate sequence

for V.32terbo can cause handshake failure. Use the #V command to include or exclude

V.32terbo mode from the handshake.

#V0 includes V.32terbo mode in the handshake.

#V1 excludes V.32terbo mode from the handshake.

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Chapter 3 - AT Commands

3.9 RS-232 Interface Commands

These commands define how am MT2834MR6 modem will use and respond to standard RS-232 signals.

&Cn

Carrier Detect Control

n = 0, 1, 2, or 4

Default: &C1

The &C command lets you control the Carrier Detect (CD) signal on the RS-232/V.24

interface. Normally, CD goes high when the modem detects a carrier on the

communications link, and drops when it loses the carrier. By using &C, however, you can

force the signal to stay high, or to drop momentarily when the remote modem disconnects.

(This option is useful with some CBX phone systems and mainframe front ends, which

require CD to act in this manner). You can also force the modem to reset when the CD

signal drops.

&C0 forces CD high.

&C1 allows CD to act normally—to go high when the modem detects a carrier, and to drop

when it loses the carrier.

&C2 causes CD to drop for one second on disconnect, and then go high again. (If you want

to set the drop time to something other than one second, change register S24).

&C4 resets the modem when CD drops.

&Dn

Data Terminal Ready Control

n = 0, 1, 2, or 3

Default: &D2

The Data Terminal Ready (DTR) signal on pin 20 of the RS-232/V.24 interface must be

high, or “on,” in order for the modem to operate. A high DTR signal tells the modem that the

computer it is connected to is ready to communicate through the modem.

The DTR signal can also be used to cause the modem to reset to its default parameters, as

if you had given the modem an ATZ command.

&D0 (or &D) causes the modem to ignore DTR.

&D1 causes the modem to hang up when DTR drops. While DTR is low, the modem

accepts commands, but will not dial or auto-answer until DTR goes high again.

&D2 acts the same as &D1.

&D3 causes the modem to reset when DTR drops . It will also hang up if it is online.

&Rn

Clear to Send Control

n = 0, 1, or 2

Default: &R1

The &R command lets you control the state of the Clear to Send (CTS) signal on pin 5 of the

RS-232/V.24 interface. Normally, CTS follows RTS when the modem is online. You have

three choices. You can force the signal high, allow it to act normally, or set it to stay high

until the modem disconnects, go low momentarily, and then go high again. The last option

is useful with CBX phone systems and mainframe front ends that require CTS to act in this

manner.

&R0 lets CTS act normally, that is, to follow RTS.

&R1 forces CTS high. When the modem goes online, CTS still provides flow control.

&R2 lets CTS drop on disconnect for the time set by register S24, then go high again.

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Chapter 3 - AT Commands

&Sn

Data Set Ready Control

n = 0, 1, or 2

Default: &S1

Use the &S command to control the state of the Data Set Ready (DSR) signal on the RS-

232/V.24 interface. Normally, DSR follows CD. You can force the signal high; allow it to act

normally; or set it to stay high until the modem disconnects, go low momentarily, and then

go high again.

&S0 forces DSR high.

&S1 allows DSR to act normally, that is, to follow CD.

&S2 sets up DSR so that it drops for one second on disconnect and then comes up again.

(If you want to set the drop time to something other than one second, change register S24.)

&RFn

CTS/RTS Interaction Control

n = 0 or 1

Default: &RF1

In normal operation, Clear to Send (CTS) follows Request to Send (RTS) when the modem

is online. In other words, if RTS goes off, CTS goes off. In some applications, however, it is

necessary for CTS to operate independently of RTS.

&RF0 enables CTS to follow RTS.

&RF1 enables CTS to operate independently of the state of RTS. See the &R command for

control of CTS.

&SFn

DSR/CD Interaction Control

n = 0 or 1

Default: &SF0

Normally, the Data Set Ready (DSR) signal follows the Carrier Detect (CD) signal. In other

words, if CD goes high, DSR goes high. In some applications, however, it may be

necessary for DSR to operate independently of CD.

&SF0 enables DSR to follow CD.

&SF1 enables DSR to operate independently of CD. For control of DSR, see the &S

command.

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Chapter 3 - AT Commands

3.10 Error Correction and Data Compression Commands

You can configure a modem to any of three different V.42 modes of operation (each mode can be with or

without compression). They are the non-error correction, autoreliable, and reliable modes. You can also turn

data compression on or off.

&En

Error Correction Modes

n = 0, 1, or 2

Default: &E1

Select the modem’s error correction mode using the &E0, &E1, or &E2 command.

&E0 disables the modem’s V.42 error correction capabilities, and the modem functions as a

non-error correction modem.

&E1 enables autoreliable mode. During the handshaking procedures at the start of the

online connection, the modem queries whether the other modem is using V.42 error

correction. If the modem determines that the other modem is using V.42, it switches itself

into reliable (V.42) mode and enables error correction. If it determines that the other modem

is not using V.42, the modem remains in non-error correction mode.

&E2 enables reliable mode, in which the modem uses its V.42 error correction capabilities

for all transmissions. In reliable mode, the modem must be connected to a modem with a

V.42 protocol (MNP or LAP-M).

The V.42 standard includes MNP Class 3 and 4 and LAP-M error correction methods. The

V.42 mode select command (#L) selects which type of error correction the modem uses for

transmissions.

&En

Data Compression

n = 14 or 15

Default: &E15

Data compression is normally enabled, providing &E1 (autoreliable mode) or &E2 (reliable

mode) has also been selected. However, you may wish to turn it off in certain

circumstances.

&E14 disables data compression.

&E15 enables data compression.

#Ln

V.42 Error Correction Modes

n = 0–3

Default: #L0

The #L command selects the V.42 error correction method (MNP or LAP-M) the modem

uses when originating a call. In answer mode, the modem ignores the #L command and

accepts whichever V.42 mode, MNP or LAP-M, the originating modem offers.

#L0 causes the modem to negotiate the V.42 error correction method with the answering

modem, and to begin negotiation with LAP-M. If both modems have LAP-M capability, the

modems will use LAP-M mode. If one or both modems do not have LAP-M capability and

both have MNP, the modems will use MNP.

#L1 enables MNP error correction and disables LAP-M.

#L2 enables LAP-M error correction and disables MNP.

#L3 enables LAP-M error correction and disables MNP, but skips the V.42 detection phase

used by the other commands. Both modems must be set with #L3.

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Chapter 3 - AT Commands

$En

V.42 Error Correction at 300 bps

n = 0 or 1

Default: $E0

At 300 bps, error correction is not normally used.

$E0 disables 300 bps/V.42 error correction altogether.

$E1 enables the modem to function at 300 bps in non-error correction (&E0), autoreliable

(&E1), or reliable (&E2) mode.

$An

Autoreliable Buffering

n = 0 or 1

Default: $A0

In autoreliable mode, the modem has four seconds to establish a reliable connection, after

which the modem drops to non-error correction mode. Any data received during this period

will normally be discarded. The $A command causes the modem to buffer (store) data that

is received during the autoreliable time-out period. This data is then output by the modem

after the CONNECT message.

$A0 discards the data received during the autoreliable time-out period.

$A1 buffers data received during the autoreliable time-out period.

$Fn

Autoreliable Fallback Character Enable/Disable

n = 0 or 1

Default: $F0

In autoreliable mode, the modem has four seconds to establish a reliable connection. If a

single carriage return is received from the remote modem during this period, the

autoreliable modem assumes that the remote modem is not in reliable mode, and drops to

non-error correction mode. The carriage return is the only character that causes the modem

to drop to non-error correction mode. Any other data is either buffered or discarded.

Use the $F command to enable this feature.

You can use the autoreliable fallback character ($F) and autoreliable buffering ($A)

commands together to cause the modem to buffer all data received up until the carriage

return, and then drop to non-error correction mode. All data received is then output

following the CONNECT message.

$F0 causes the modem not to fall back to non-error correction connect if a carriage return is

received.

$F1 causes the modem to fall back to non-error correction connect if a carriage return is

received.

$Rn

Retransmit Count

n = 0 or 1

Default: $R0

If errors are received during a reliable connection, the modem re-sends the block of data

that contained an error. If another error occurs, it re-sends the block again. The modem

counts the number of times that a data block is re-sent.

$R0 causes the modem to disconnect if the same block of data is re-sent 12 times without

being received properly, on the assumption that the line is unsuitable for transmission.

$R1 causes the modem to disable the retransmit counter, so that the modem keeps trying to

send data and will not abort, no matter how many times the same block is resent. Type

AT$R0 to disconnect the modem if all attempts to re-send the block fail.

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Chapter 3 - AT Commands

3.11 Speed Conversion Commands

Speed conversion allows the MT2834MR6 to communicate at a fixed speed through the serial port while

communicating at an independent speed over the online communications link. Speed conversion is

necessary for data compression, since data compression requires data to be sent from the computer to the

modem at a rate up to four times faster than the modem’s transmission speed.

Speed conversion is also useful for an autoanswer modem connected to a computer that does not have

autobaud capability, since the computer must be set at a fixed baud rate regardless of the speed at which the

modem communicates over the phone line.

$BAn

Baud Adjust

n = 0 or 1

Default: $BA0

Turning baud adjust off turns speed conversion on; turning baud adjust on turns speed

conversion off.

When baud adjust is on, the modem matches its RS-232 serial port speed to any changes

in the computer’s serial port speed in originate mode, or to the speed of the originating

modem when it’s in answer mode. With baud adjust on, the speed at which the modem

communicates over the phone line is always the same as the speed at which it

communicates via its RS-232 serial port.

When speed conversion is on, the modem does not adjust its speed at the serial port to

match its transmission speed. Serial port speed and transmission speed can therefore be

set independently. Speed conversion is necessary for a high speed modem that is

connected to a limited speed serial port.

$BA0 turns baud adjust off and speed conversion on.

$BA1 turns baud adjust on and speed conversion off.

$MBn

Modem Baud Rate

n = speed in bits per second

Default: $MB33600

The $MB command sets a modem’s initial transmission speed for originate mode. In V.32

mode (9600 bps), it also sets the transmission speed for answer mode. With speed

conversion on, this transmission speed can be different from the serial port speed.

When the modem answers a call from another modem, it automatically switches its

transmission speed to match the calling modem. However, if the MT2834MR6 originates a

call to another modem that is unable to connect at the same transmission speed, the

MT2834MR6 automatically drops to a lower speed in an attempt to match the speed of the

other modem.

Speed conversion must be on for this command to work. If baud adjust is on ($BA1), speed

conversion is off and a modem baud rate command will be ignored. The S48 register also

can affect maximum transmission speed. See Chapter 4.

$MB75

ITU-T V.23 mode

1200 bps

4800 bps

9600 bps

14,400 bps

$MB300

300 bps

$MB1200

$MB4800

$MB9600

$MB14400

$MB19200

$MB33600

$MB2400

$MB7200

$MB12000

$MB16800

$MB28800

2400 bps

7200 bps

12,000 bps

16,800 bps

28,800 bps

19,200 bps

33,600 bps (default)

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Chapter 3 - AT Commands

$SBn

Serial Port Baud Rate

n = speed

Default: $SB57600

The $SB command sets the speed of the MT2834MR6’s serial port in both originate and

answer modes. Speed conversion allows you to set this serial port baud rate at a fixed

speed of up to 115,200 bps, regardless of the modem’s transmission speed setting.

For this command to work, the modem’s baud adjust feature must first be turned off with the

$BA0 command. When baud adjust is on, as soon as the modem receives its first AT

command, it automatically adjusts its serial port baud rate to match the speed of the

computer or terminal to which it is connected. However, in applications such as automatic

answer, the modem may not receive AT commands. In this case it is helpful to be able to

preset the serial port baud rate with the $SB command.

In addition to setting the modem’s serial port speed, this command sets the speed at which

the modem issues command mode responses (result codes).

The MT2834MR6 accepts AT commands at any speed, regardless of the speed preset by

the $SB command. If the modem receives a command at a speed different from the preset

speed, the modem switches its serial port baud rate to match the new command speed,

even though the baud rate value stored by the $SB command remains the same. This

provides you with a convenient way to switch the serial port speed while still making it easy

to automatically return to the original speed the next time the modem is powered up or

reset.

$SB300

300 bps

2400 bps

9600 bps

38,400 bps

115,200 bps ( default)

$SB1200

$SB4800

$SB19200

$SB57600

1200 bps

4800 bps

19,200 bps

57,600 bps

$SB2400

$SB9600

$SB38400

$SB115200

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Chapter 3 - AT Commands

3.12 Immediate Action Commands

Use these commands to get information about AT commands and the current settings of the modem. For

additional immediate action commands, see “Line Probe Commands.”

Repeat Last Command

Default: None

Type A/ to repeat the previous command. Do not precede this command with AT or press

ENTER to execute it.

Inquire Product Code

n = 0, 1, or 2

Default: none

Some systems or software packages automatically check the identification of the modem by

using the I command. Besides using it to check the modem ID, you can use the I command

to check the version number of the modem’s built-in software, known as firmware.

ATI0 or ATI requests the modem’s ID number.

ATI1 requests the modem’s firmware version number. You can use this command to identify

your modem’s firmware level when calling Technical Support.

ATI2 requests the product name, such as MT2834MR6.

ATI5 requests the digital signal processor version number.

L5, L7

List Current Operating Parameters

Default: none

The L5 and L7 commands cause your modem to list its current operating parameters. These

lists are useful when you are changing communications software, or when you are

changing modem default settings. All modem configuration parameters are listed.

ATL5 lists the modem’s current operating parameters.

ATL7 lists additional modem parameters.

List Current S-Register Values

Default: none

ATL6 lists the current values in the modem’s S-registers. This information can be very

useful if you wish to change S-register values.

List Online Diagnostics

Default: none

The L8 command displays the modem’s online status. You can print this display and use it

as a modem status report or as diagnostic information (such as when calling Technical

Support).

To enter this command while online, type +++ATL8<CR>. Your modem’s online status will

be displayed, listing current operating conditions such as link type, line speed, serial speed,

line quality, and reason for last disconnect.

If you type +++ATL8 with the modem online, the current online status will be displayed. If

you type ATL8 with the modem in command mode, the most recent online status will be

displayed. If you type ATL8 immediately after modem power-up, the message NO

INFORMATION AVAILABLE will be displayed.

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Chapter 3 - AT Commands

&RN

&RR

Rate Renegotiation

Default: none

The &RN command forces the modem to perform a rate renegotiation while online. To issue

it, you must first escape to command mode by issuing the +++AT<CR> command.

Retrain

Default: None

The &RR command forces the modem to perform an immediate retrain while online. To

issue it, you must first escape to command mode by issuing the +++AT<CR> command.

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Chapter 3 - AT Commands

3.12 Flow Control Commands

Flow control refers to the techniques used by data terminal equipment and the modem to pause and resume

the flow of information between them. It prevents a device from accepting more data than it can handle. The

modem implements flow control in both directions. When the modem halts the flow of data, it is called flow

control, and when the computer halts the flow, it is called pacing.

&BSn

Maximum Reliable Block Size

n = 0 or 1

Default: &BS1

When the modem is in reliable mode, use the &BS command to set the maximum size of a

data block. MNP Class 3 sends a 64-character block, while Classes 4 and 5 normally send

blocks of 256 characters or less. Reducing the block size for MNP 4 and 5 may improve

overall throughput whenphone lines are noisy; however, it also could slow data transfer if

line quality is good.

&BS0 sets the maximum transmit block size to 64 characters.

&BS1 sets the maximum transmit block size to 256 characters.

$EBn

Asynchronous Word Length

n = 0 or 1

Default: $EB0

The MT2834MR6 can operate with either a 10-bit format (one start bit, seven data bits, one

parity bit, and one stop bit) or an 11-bit format (one start bit, eight data bits, one parity bit,

and one stop bit) in both command and online modes.

$EB0 enables a 10-bit format It automatically detects parity when an AT command is

issued.

$EB1 enables an 11-bit format.

&E3

&E4

Flow Control Disable

The &E3 command completely disables data flow control initiated by the modem.

Hardware Flow Control

Factory default. The &E4 command enables the modem’s use of the Clear to Send (CTS)

signal on the RS-232/V.24 interface to regulate data flow. When CTS drops, data flow is

suspended until the signal goes high again. This method of flow control works in

conjunction with pacing (i.e., computer-initiated flow control), which uses the Request to

Send (RTS) signal on the RS-232/V.24 interface. Hardware flow control cannot be enabled

unless an active error correction protocol is selected.

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Chapter 3 - AT Commands

&E5

XON/XOFFFlowControl

XON/XOFF flow control is an in-band method of data flow regulation used by the modem or

computer (i.e., by flow control or pacing). If you issue the &E5 command to the modem, it

will respond to XON/XOFF pacing, and use XON/XOFF characters as its own method of flow

control to the computer.

In-band data regulation means that the XON and XOFF characters (^Q and ^S, respectively)

are inserted into the stream of data rather than using separate control lines. When an XOFF

character is detected, the data stream is suspended until an XON character is detected. The

drawback to using this method of pacing is that some files may contain these characters. If

such a file is transferred using a modem, the file transfer can be suspended indefinitely.

&En

XON/XOFFPass-Through

n = 6 or 7

Default: &E6

When XON/XOFF pacing is active, the local modem has two options regarding the XON and

XOFF characters. It can respond to and discard the characters from the computer, or it can

respond to the characters and pass them through the datacomm link to the remote modem,

thereby pacing the remote modem as well.

&E6 causes the modem to respond to and discard the XON and XOFF characters.

&E7 causes the modem to respond to the characters and pass them through the data link to

the receiving modem.

&En

Hewlett Packard ENQ/ACK Pacing

n = 8 or 9

Default: &E8

If the MT2834MR6 is used with Hewlett Packard (or compatible) equipment, it can be

configured to respond to ENQ/ACK pacing as a complement to any other form of active flow

control or pacing. In that case, pacing from the Hewlett Packard equipment is processed

according to the HP protocol.

&E8 causes the modem to ignore ENQ/ACK pacing.

&E9 causes the modem to respond to the ENQ (^E) and ACK (^F) characters.

&En

Non-Error Correction Mode Flow Control

n = 10 or 11

Default: &E10

When two modems are connected in non-error correction mode, XON/XOFF flow control

can be used as a complement to XON/ XOFF pacing.

&E10 disables non-error correction mode flow control.

&E11 enables non-error correction mode flow control.

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Chapter 3 - AT Commands

&En

Pacing (Computer-Initiated Flow Control)

n = 12 or 13

Default: &E13

Pacing is the means by which the DTE (data terminal equipment—your computer or

terminal) regulates the stream of incoming data. It is only enabled when the modem has

some form of flow control active, such as RTS/CTS or XON/XOFF. When pacing is enabled,

the modem responds to the DTE’s pacing signals. When pacing is disabled, the modem

ignores any pacing signals from the DTE.

&E12 disables pacing.

&E13 enables pacing.

#Xn

Number of XOFF Characters Sent

n = 0 or 1

Default: #X0

The #X command allows the modem to send either a single or multiple XOFF characters

when the modem’s buffer becomes full. When the buffer is full, the next character received

causes an XOFF character to be sent. In default mode, only one character is sent until the

buffer reaches the XON level; however, it is also possible to send one XOFF character for

every character received after the buffer is full.

#X0 causes only a single XOFF character to be sent after the buffer is full.

#X1 causes one XOFF character to be sent for every character received after the buffer is

full.

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Chapter 3 - AT Commands

3.13 Escape Sequences

Escape sequences (escape codes) cause the modem to enter command mode from online mode without

disconnecting the call. There are two local escape sequences used by the modem, +++AT<CR> and

<BREAK>AT<CR>, and one remote escape sequence, %%%AT<CR> (see “Remote Configuration”).

+++AT<CR>

In-Band Escape Sequence

When the modem is online with a remote modem, enter command mode (without

disconnecting the call) by typing this escape code. The default escape code is three plus

signs (+++) followed by the letters AT, up to 10 command characters and ENTER. The

modem escapes to command mode, executes the command (if any), then remains in

command mode.

<BREAK>AT<CR> Out-of-Band Escape Sequence

An alternate escape method uses a break signal as the escape code. The break signal is

ten or more zero bits issued by data communications software. This allows the DTE to

signal the modem without the modem interpreting data characters as modem control

characters. The break signal is followed by the letters AT, up to 60 command characters,

and ENTER. The modem executes the command and immediately returns to online mode,

unless the command is to hang up and/or reset the modem (an H or Z command). In the

latter case, the modem escapes to command mode after executing the H or Z command.

%En

Escape Sequence Options

n = 0–5

Defaults: %E1 and %E4

Optional settings cause the modem to respond to the <BREAK> method, or respond to

either the +++ or the <BREAK> methods, or for the modem to ignore both methods and not

escape. The %E command is used to select these options as follows:

%E0

Modem doesn’t escape

%E1

%E2

+++ AT<CR> escape method (factory default).

<BREAK> escape method.

%E3

%E4

%E5

Either +++ or <BREAK> escape methods.

Disables OK response to +++ (factory default).

Enables OK response to +++.

%E1 %E5

%E3 %E5

Enables +++ method and OK responses to +++.

Enables +++ or <BREAK> method and OK responses to +++.

Force Answer Mode

Use the A command to force the modem into answer mode. Type ATA when in command

mode to immediately bring the modem off-hook, out of command mode and into online

answer mode, transmitting the carrier signal over the phone line. If no responding carrier

tone is received within forty-five seconds (or by the time you have specified in register S7),

the modem stops transmitting and hangs up, returning to command mode.

Go Back Online

Use the O command to bring the modem out of command mode and back into online mode.

The O command reverses the result of entering the escape code. The O command brings

the modem into whichever online mode (originate or answer) that it was in prior to entering

command mode.

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Chapter 3 - AT Commands

3.14 Remote Configuration Commands

When you are online with another Multi-Tech modem, you can issue AT commands to it by sending a remote

configuration escape sequence. The remote modem responds by displaying a menu and asking for a setup

password. The MT2834MR6 has two default passwords. Please note that if you change them, you cannot

retrieve them by resetting the modem by using AT&W1; you must know the new passwords to make any

further changes. For further information on remote configuration, see Appendix I, “Remote Configuration.”

%%%AT<CR> Remote Configuration Escape Sequence

Enter the remote configuration escape sequence to initiate remote configuration when you

are online with another Multi-Tech modem. The default escape sequence used by the

MT2834MR6 is three percent signs (%%%) followed by the letters AT and ENTER. The

remote configuration escape character, which is stored in register S13, can be changed

either locally or remotely for greater security.

#Ixxxxxx

Change Login Password

xxxxxx = password

Default: #IMULTI-TECH

Use the #I command to enter or change the remote configuration login password.

AT#Ixxxxxx enters the current remote configuration login password, where xxxxxx

represents the password. If the password is wrong, the remote modem responds with

ERROR; if it is correct, the remote modem responds with OK, and you can proceed with the

#S command.

AT#I=xxxxxx stores a new remote configuration login password, where xxxxxx represents

the password. The password is case sensitive, and can be any combination of upper and

lower case keyboard characters. It must be six to ten characters in length.

#Syyyyyy

Change Setup Password

yyyyyy = password

Default: #SMODEMSETUP

Use the #S command to enter or change the remote configuration setup password. Before

you can use it, you must enter the login password using the #I command.

AT#Syyyyyy enters the current remote configuration password, where yyyyyy represents

the password. If the password is wrong, the remote modem responds with ERROR; if it is

correct, the remote modem responds with OK, and you can proceed with the next command.

AT#S=yyyyyy stores a new remote configuration setup password, where yyyyyy represents

the password. The password is case sensitive, and can be any combination of upper and

lower case keyboard characters. It must be six to ten characters long.

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Chapter 3 - AT Commands

3.15 Line Probe Commands

Before V.34 negotiation, the local and remote modems use modulated calling and answering tones to

exchange capability information . If V.34 mode communication is successful, probing signals are exchanged

to identify impairments in the telephone channel. Using the results of these line probes, communication

parameters are set, including carrier frequencies and data rates used for transmission. The following

commands apply to modems only in V.34 mode.

%DPn

Read Line Probe Data

n = 0 or 1

Default: %DP0

The modem does not normally store data acquired during line probe. To examine the line

probe data using the L9, L10, or L11 commands, set the %DP1 command to read and store

line probe data.

%DP0 disables reading of line probe information during the handshake.

%DP1 enables reading of line probe information during the handshake.

%DFn

Format Line Probe Data

n = 0 or 1

Default: %DF0

Use this command to selects line probe data displayed as a graph with the Y axis showing

signal strength in dBm, or as a table with dBm values shown numerically. The graph format

shows data in 150 Hz increments from 150 Hz to 3750 Hz. The table format shows data in

75 Hz increments from 150 Hz to 3750 Hz.

%DF0 displays line probe data in graph format.

%DF1 displays line probe data in table format.

&RP

Immediate Line Probe

Default: none

This command initiates a retrain that makes the processor read line probe information for

display using the L9, L10, and L11 commands. Before issuing this command, escape to

command mode while remaining online. To combine both actions, use the following

command string: +++AT&RP<CR>.

The modem will not read and store the line probe information from this retrain unless a

%DP1 command is first issued.

Display Line Probe Data

n = 9–11

Default: none

These immediate action commands cause the modem to display line probe information

when it is in V.34 mode. The line probe information must first be read and stored by the

modem (see “Read Line Probe Data”). Data format is controlled by the Format Line Probe

Data command, %DF.

The display commands are valid only in online mode. To use them online, you must first

escape to command mode with +++AT<CR>. To return online, enter ATO.

ATL9 displays signal strength information.

ATL10 displays the signal to noise ratio (SNR).

ATL11 displays noise information.

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Chapter 3 - AT Commands

3.16 Diagnostic Commands

The MT2834MR6 has two diagnostic commands and four diagnostic modes. The power-on self-test is

activated every time power is applied. The U command selects a loopback test, while the &T command

enables a modem to respond to a loopback test from another modem. See Chapter 6, “Testing the

MT2834MR6,” for a fuller discussion. Refer to the L8 command to see how to list the diagnostic online status.

&Tn

Respond to Remote Digital Loopback Signal

n = 4 or 5

Default: &T5

The MT2834MR6 has several self-test features, discussed in Chapter 6. The &T command

enables or disables the modem’s ability to recognize the remote digital loopback (RDL) test

signal. (See Chapter 6 for remote digital loopback test procedures.)

AT&T4 lets the modem respond to an RDL signal, and places it in digital loopback.

AT&T5 causes the modem to ignore the RDL signal.

Loopback Test Modes

n = 0–3

Default: None

Loopback tests send data through the modem in such a way that it loops back to the

terminal where it was entered, testing all the circuits along the way. The U command selects

from several loopback tests. See Chapter 6, “Testing Your Modem,” for more information.

ATU0 places the modem in originate mode for the local analog loopback test.

ATU1 places the modem in answer mode for the local analog loopback test.

ATU2 performs the remote digital loopback test.

ATU3 performs the local digital loopback test.

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Chapter 4 - S-Registers

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Chapter 4 - S-Registers

4.1 Introduction

This chapter describes the MT2834MR6’s S-registers, which are small regions of memory where modem

configuration information is stored. Whereas AT commands tell a modem what to do, S-registers tell the

modem how to do it. Each S-register has a name that consists of the letter S and a number (S0, S1, S2, etc.),

hence the term S-register. Use the Sr? command to read the value stored in an S-register, and the Sr=n

command to change it.

4.2 S-Registers

Number of Rings Until Modem Answers

Unit: 1 ring

Range: 0–255

Default: 1

S0 defines the number of rings the modem waits before answering an incoming call. The

default value is one ring, which causes the modem to answer the call immediately after the

first ring. The maximum number of rings that can be configured is 255. Setting the value to

zero disables autoanswer.

RingCount

Unit: 1 ring

Range: 0–255

Default: 0

S1 counts the number of rings that have occurred. It is a “read” type of register and is

seldom, if ever, used in typical operation. Each time an incoming ring signal is detected, S1

increases its value by one, up to a maximum of 255. If you set S1 to a value other than its

default value of zero, or if the value is increasing with rings, this new value remains stored

in S1 for eight seconds after the last ring is counted, after which the value reverts back to

zero.

Escape Code Character

Unit: Decimal

Range: 0–127

Default: 43 (+)

S2 defines the escape code character by its decimal ASCII code. The default character is

the plus (+) sign (decimal 43). S2 may be set for any ASCII character. Setting an S2 value

greater than 127 results in no escape character, and therefore no means of entering

command mode from online mode without breaking the online connection, unless you use

the BREAK method. See Appendix H, “Multi-Tech Escape Methods.”

Note: If you change the S2 value, you must make corresponding changes in your data communications

software.

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Chapter 4 - S-Registers

Return Character

Unit: Decimal

Range: 0–127

Default: 13 (^M)

S3 defines the carriage return character by its decimal ASCII code. The default setting is the

^M character (decimal 13), which is the code for the ENTER key on most keyboards. S3

may be set for any ASCII character.

Note: If you change the S3 value, you must make corresponding changes in your data communications

software.

Line Feed Character

Unit: Decimal

Range: 0–127

Default: 10 (^J)

S4 defines the line feed character by its decimal ASCII code. The default setting is ^J

(decimal 10), which is the code for the line feed key on most keyboards that have such a

key. S4 may be set for any ASCII character.

Backspace Character

Unit: Decimal

Range: 0–127

Default: 8 (^H)

S5 defines the backspace character by its decimal ASCII code. The default setting is the ^H

character (decimal 8), which is the code for the BACKSPACE key on most keyboards. S5

may be set for any ASCII character.

Note: If you change the S5 value, you must make corresponding changes in your data communications

software.

Wait Time for Dial Tone

Unit: 1 second

Range: 2–255 (North America)

4–255 (International)

4–7 (U.K.)

Default: 2 (North America)

4 (International and U.K.)

S6 defines the length of time the modem waits after the ENTER key is pressed before

executing a dial command. The default setting is two seconds for North America, four

seconds elsewhere.

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Chapter 4 - S-Registers

Time for Carrier (Abort Timer)

Unit: 1 second

Range: 1–255 (U.S.A.)

1–45 (Canada and International)

1–55 (U.K.)

Default: 45 (North America and International)

55 (U.K.)

S7 determines the abort timer delay time, which is the amount of time your modem will wait

for a carrier signal before it disconnects. The default value is 45 seconds, except the U.K.

model, for which it is 55 seconds. This means that, after dialing, the modem waits for a

carrier signal for up to 45 or 55 seconds and, if none is detected, aborts the call. The

maximum S7 value is 255 seconds for the U.S.A. model, 45 seconds for Canadian and

International models, and 55 seconds for the U.K. model.

Pause Time for Comma

Unit: 1 second

Range: 0–255 (North America)

4–255 (International)

4–7 (U.K.)

Default: 2 (North America)

4 (International and U.K.)

S8 determines the length of the pause caused by a comma in a dialing command. The

default setting is two seconds for the North American model, and four seconds for the

International and U.K. models. S8 may be set for up to 255 seconds. S8 also defines the

length of time the modem waits before retrying a call after it detects a busy signal. Some

computer systems need more than two seconds to reset, in which case you should increase

the value of S8.

Carrier Detect Response Time

Unit: 100 ms

Range: 1–255

Default: 6

S9 determines the time delay between when the modem first detects a valid incoming

carrier signal and when the modem turns on its Carrier Detect circuit. The default setting is

600 milliseconds (six units of 100 ms each). S9 may be set for up to 25.5 seconds.

S10

Carrier Loss Disconnect Delay Time

Unit: 100 ms

Range: 1–254, 255

Default: 7

S10 defines the length of time after a loss of carrier signal before the modem disconnects.

The default setting is 700 ms (seven units of 100 ms each). Maximum delay is 25.4 seconds

(decimal 254). Setting the S10 value to 255 causes the modem not to disconnect with loss

of carrier.

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Chapter 4 - S-Registers

S11

Tone Dialing Spacing and Duration

Unit: 1 ms

Range: 1–255 (U.S.A.)

80–255 (Canada, U.K., International)

Default: 70 (U.S.A.)

80 (Canada, U.K., International)

S11 sets the speed of tone dialing (spacing and tone duration times). The default value is

70 units for domestic models and 80 units for Canadian and International models, where

each unit is one ms. In other words, for domestic modems, each tone is sustained for 70 ms

followed by a 70 ms pause. The minimum S11 value allowed by most telephone systems is

50 ms (50 units). Very few telephone systems can handle anything faster than that. The

maximum S11 value is 255 ms (255 units).

S13

Remote Configuration Escape Character

Unit: Decimal

Range: 0–127

Default: 37 (%)

S13 defines the remote configuration escape character by its decimal ASCII code. The S13

default is the percent character (decimal 37). When you enter the S13-defined character

three consecutive times from a remote site, your modem responds with its remote

configuration procedure. A value of 0 disables remote configuration.

S17

Changing Break Time

Unit: 10 ms

Range: 1–255

Default: 25 (250 ms)

S17 defines the break time (space) the modem sends the DTE when it receives a break

signal from a remote modem. Break duration is adjustable in 10 millisecond increments.

The default is set to 25, for a 250 millisecond break.

S24

PBX/CBX Disconnect Drop Time for DSR/CTS/CD

Unit: 50 ms

Range: 0–255

Default: 20 (1 second)

Some PBX and CBX phone systems require the modem’s DSR, CTS, and/or CD signals to

drop briefly when calls are disconnected. The MT2834MR6’s &R, &S, and &C commands

can cause the modem to drop these signals for a specified time upon disconnect, and then

bring the signals up again. S24 defines the length of time that the signals drop. The default

setting of 20 results in a one-second drop time, which is what most PBX/CBX systems with

this requirement need.

S25

DTR Dropout Time

Unit: 100 ms

Range: 0, 1–255

Default: 0 (50 ms)

S25 sets the amount of time that DTR must be dropped before the modem disconnects.

Typically, a disconnect occurs when DTR is dropped for 50 milliseconds or more. This

dropout time can be increased up to a maximum of 25.5 seconds. The S25 unit value for

zero is 50 ms. For values from 1 through 255, the unit value is 100 ms.

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Chapter 4 - S-Registers

S30

Inactivity Timer

Unit: 1 minute

Range: 0, 1–255 minutes

Default: 0 (disabled)

S30 can be used to cause the modem to disconnect if no data is transmitted or received for

a specified time. S30 runs during both reliable and non-error correction connections. The

timer restarts any time a data character passes through the serial port (either sent or

received). If noise on the phone line causes an error to be received during non-error

correction mode, this also will restart the S30 timer. The factory default of zero disables the

timer.

S32

S34

Time Lapse for Escape Sequence

Unit: 100 ms

Range: 0–255

Default: 20 (2 seconds)

S32 sets the time period to validate the escape sequence. If the S32 time interval expires

before you press ENTER, then the escape sequence is aborted. The default is two seconds.

Command Buffer Length After Online Escape Sequence

Unit: Decimal

Range: 0–60

Default: 10

Sets the number of characters allowed in an AT command after an in-band online escape

(+++ method). If the number of characters after “AT” exceeds the S34 buffer length value,

then the buffer is flushed and the escape sequence is aborted.

S36

DTR Busy-Out Time

Unit: 1 second

Range: 0–255

Default: 0 (disabled)

S36 sets the time between when DTR goes inactive and when the modem goes off-hook.

The DTR busy-out feature is disabled when S36 is set to 0.

Normally, when the DTR signal from the computer goes inactive, the modem goes on-hook

after a time that is set by S25. If S36 is set for a non-zero time, the modem then waits for the

time set by S36; if DTR has not gone active again in that time, the modem goes off-hook,

causing a busy signal for callers. The busy-out state ends when DTR goes active again.

S37

DTR Busy-In Time

Unit: 1 second

Range: 0–255

Default: 5

S37 sets the time between when DTR goes active and when the modem goes on-hook, if

S36 has caused it to go off-hook.

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Chapter 4 - S-Registers

S43

Force V.34 Connect Speed

Unit: N/A

Range: 0, 33, 31, 28, 26, 24, 21, 19, 16, 14, 12, 96, or 48

Default: 0 (disabled)

S43 forces the modem to attempt to connect at a fixed speed in V.34 mode. The two-digit

value corresponds to the first two digits of the speed (S43=21 sets the connect speed to

21.6K bps, S43=96 sets it to 9600 bps, etc.). The factory default of zero disables this feature

and allows the modem to establish the best speed for the conditions.

Note: The $MB command overrides S43 if the $MB command is set to a speed other than 33,600 bps.

S48

Maximum V.34 Connect Speed

Unit: N/A

Range: 0, 33, 31, 28, 26, 24, 21, 19, 16, 14, 12, 96, or 48

Default: 0 (disabled)

S48 sets the maximum speed in bps at which the modem can attempt to connect in V.34

mode. The two-digit value corresponds to the first two digits of the speed (S48=26 sets the

maximum connect speed to 26.4K bps, S48=48 sets it to 4800 bps, etc.). This register

allows you to set lower speeds for line conditions that will not support higher V.34 speeds

such as 33.6K, 31.2K, 28K, 26.4K, or 24K. The factory default of zero disables this feature

and allows the modem to establish the best speed for the conditions (in effect, it sets a

maximum connection attempt of 33.6K).

S94

Out-of-Service Time

Unit: 1 second

Range: 0–254, 255

Default: 45

S94 sets the maximum number of seconds, from 0 through 254, that the modem remains out

of service when the *H1 command is active. A value of 255 causes the modem to remain

out of service indefinitely. However, if the modem receives an enable command from the

management program while the modem is out of service, the modem returns to service

immediately, before the S94 time expires.

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Chapter 4 - S-Registers

4.3 Reading and Assigning S-Register Values

Use the S command to assign a value to an S-register and to read an S-register’s current value.

To read an S-register value, in terminal mode, type S, the S-register number, and a question mark (?), and

press ENTER. For example, to display the value of register S7, type ATS7? and press ENTER. The answer

will appear as a three-digit decimal number (e.g., 045).

To assign a new value to an S-register, type S, the S-register number, an equals sign (=), and a decimal

number. Convert all ASCII characters to their decimal equivalents before entering them. S-register decimal

values are 0–127 for ASCII characters, and 0–255 for numeric values. To make the change permanent, use

the &W0 command.

4.3.1 Examples of Assigning Values

1. Example: To assign longer pauses caused by the comma in a dial command—five seconds instead of

two. Type ATS8=5 to assign 5 as the value for register S8. The modem will now pause five seconds for

every comma in a dial command.

2. Example: To configure the modem to answer incoming calls after the thirtieth ring instead of after the first

ring. Configure register S0 with a value of 30, type ATS0=30 and press ENTER.

3. Example: International calls that take a long time to connect. The register S7 (abort timer) factory default

setting of 45 seconds is insufficient; the abort timer times out and cancels the call before a connection is

made. To change the S7 value to 55 seconds, type ATS7=55 and press ENTER. Now, after dialing, the

modem allows 10 more seconds for a carrier signal before aborting the call. The additional 10 seconds

should provide enough time for international calls.

4.3.2 Examples of Reading Values

1. To verify that you entered the value correctly in the preceding examples, type ATS8? and press ENTER

in the first example, ATS0? in the second example, and ATS2? in the third example. You should receive

the responses 005, 030, and 055, respectively.

2. When configuring S-registers, it is a good practice to include the verification read command in the same

command string as the configuration assignment command. In the three preceding examples, type

ATS8=5S8?, ATS0=30S3?, and ATS7=55S7?, respectively.

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Chapter 4 - S-Registers

4.4 AT Commands Affecting S-Registers

For maximum throughput, the MT2834MR6's default configuration is for originating a call to another 33,600

bps modem that supports error correction, data compression, and flow control. If the receiving modem is not

compatible, the MT2834MR6 can match any ITU-T or Bell standard modem (but not proprietary protocols).

If you require a different configuration for your application, for example, if you want to use an MT2834MR6

modem strictly as an autoanswering device, or for service that does not support error correction, you can

selectively change the command parameters and S-register values in active memory and save the new

values by using the &W command.

The &W0 (or &W) command stores all current AT command and S-register values into nonvolatile random

access memory (NVRAM) and configures the modem so that it reads your custom settings in NVRAM when

the modem is turned on or when it is reset with the Z command. (The &F reset command will continue to read

the factory default settings in read-only memory [ROM] unless you also store the &F9 command. See Chapter

3.) For convenience, you can incude the &W command in the same command string that sets the new values

in active memory, as in the following example:

AT&E2$SP1#L3$R0$MB19200$SB115200$EB1S0=10&W0<CR>

The &W1 command erases your custom settings in NVRAM the next time the modem is turned off or reset,

causing the modem to read the factory default settings in ROM when it is subsequently turned on or reset.

For further information on how the &W command interacts with the reset commands, see Table 3-2.

Before you use the &W command, check the modem’s current operating parameters by using the L5, L6, and

L7 commands.

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Chapter 5 - Error Correction,

Data Compression & Speed Conversion

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.1 Introduction

The MT2834MR6 has intelligent features beyond those of the AT command set described in Chapter 3. This

chapter describes high performance features and commands that provide error correction, data compression

and speed conversion capabilities. The remainder of this chapter describes these features and the

commands that implement them, as well as related commands.

The MT2834MR6’s error correction complies with the ITU-T V.42 standard. V.42 actually uses two error

correction protocols: LAP-M and MNP Class 3 & 4. MNP Class 3 & 4 error correction emerged as the industry

standard among modem manufacturers over the past decade. It is now in the public domain, and has been

implemented in dozens of modem brands with world wide installations in the hundreds of thousands of units.

LAP-M error correction is similar to MNP Class 3 & 4.

The MT2834MR6 provides two types of data compression: ITU-T V.42bis and MNP Class 5. V.42bis data

compression is newer; it requires concurrent LAP-M error correction. V.42bis is a very efficient data

compression technique that can provide up to 4-to-1 compression, depending on the type of data being

transmitted. MNP Class 5 data compression requires concurrent MNP Class 3 & 4 error correction. It is an

older and more established standard that offers data compression in the 2-to-1 range, which also depends

on the type of data being transmitted.

Speed conversion allows the modem to operate at one speed over the telephone lines and another speed at

the RS-232 serial port. This allows the computer or terminal to communicate with the modem at a fixed speed

of up to 115,200 bps, while the modem operates at various speeds up to 33,600 bps. Speed conversion is

vital if data compression is to be effective, since your terminal or computer must send data to the modem at a

higher speed than the modem is sending it over the phone line.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.2 How V.42 Detects and Corrects Errors

Some of the better known software-based error-correction protocols include Xmodem and Kermit (for

asynchronous file transfer software), X.PC (Tymnet’s asynchronous software protocol), and SDLC and HDLC,

two popular synchronous protocols common in the IBM mainframe environment. V.42 is functionally similar to

SDLC and HDLC, with some extras.

The main advantage of hardware-based V.42 error correction over these software-based protocols is in

throughput. Throughput is the effect that the use of the protocol has on the overall data rate. For example,

V.42 transmissions using a 2400 bps modem have an effective throughput of about 2600 bps. The same

modem using software-based X.PC would have an effective throughput of less than 2400 bps. Another way

of stating it is that V.42 has an efficiency of about 108%, while X.PC has an efficiency of about 91%.

Simply stated, one modem with V.42 sends coded data to another modem with V.42, and the receiving

modem is able to determine if there are any errors. If there are, the receiving modem tells the sending modem

to re-send the errant data until it’s correct.

Technically speaking, when using V.42, the sending modem uses a polynomial function to calculate a 16-bit

number that is a function of all the data sent in a particular message or block. It then sends those sixteen bits

at the end of the block, which can include up to 256 characters. The other V.42 modem, as it is receiving the

block, calculates its own version of the 16-bit number. Then it compares its number with the 16-bit number

sent with the block. If the numbers are the same, the block is free from errors. If the numbers are different, an

error has occurred somewhere in the block. That’s how errors are detected.

Once an error is detected, the receiving modem’s V.42 error correction is activated.

For all practical purposes, the result of the V.42 error correction protocol is error-free transmission. Using the

16-bit redundancy check, it will detect every error which is 16 bits or smaller with 100% probability. As a

result, the chances of an error occurring are actually so small that you can ignore them.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.3 Data Compression

The MT2834MR6 has both V.42bis and MNP class 5 data compression. ITU-T V.42bis is an international

data compression standard that can provide data compression of up to four to one in certain types of data.

MNP class 5 is a proprietary technique for data compression that provides a data compression capability of

two-to-one.

The MT2834MR6 must be in error correction mode before it can compress data (LAP-M error correction for

V.42bis data compression or MNP error correction for MNP 5 data compression). By using the #L command,

you can select which error correction to use.

The type of file transfer protocol used to send and receive data has a big effect on the speed gain due to

compression. In general, a protocol that uses large data blocks transfers files quicker. For example,

YMODEM sends 1000 characters per block. It also helps to have the serial port of the receiving modem set to

the highest possible speed (115,200 bps), if the sending modem is set to a lower speed.

To achieve a data rate that is higher than the modem baud rate, turn Baud Adjust off ($BA0) and operate the

serial port at a higher speed than the modem baud rate. For the MT2834MR6, set the serial port to 115,200

bps ($SB115200).

Data compression works by locating repeated strings of characters and repeating these strings using shorter

codewords. To use data compression, the modem must to be driven at full capacity. In other words, the data

must be present at enough volume and speed to get maximum compression benefits, as when using file

transfers or batch operations. Speed conversion must be on to operate the port at a higher speed than the

modem connection speed.

When operating the serial port at a higher speed than the modem baud rate, some type of flow control must

be used, otherwise data can be lost. (See &E4 and &E5 commands.)

To enable data compression, type AT&E15 and press ENTER; to disable data compression, type AT&E14

and press ENTER.

Note: For data compression to take place, both the answer and the originate modems must have data

compression and error correction enabled.

5.4 MNP Classes

The MNP protocol is divided into several classes. The classes you might encounter today in full duplex dial-

up in 1200, 2400 and 9600 bps modems are Classes 3 through 5. When modems equipped with MNP start

communicating, they negotiate operation to the highest common MNP class between them and operate at

that level.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.5 V.42 Mode Select Command (#L)

The V.42 Mode Select command (#L) selects which type of error correction your MT2834MR6 will use for

transmissions. The V.42 standard implements both MNP Class 3 & 4 and LAP-M error correction protocols.

When you execute one of the #L commands, you instruct your MT2834MR6 how to operate with each

protocol. For example, the factory default setting (#L0) tells your MT2834MR6 to negotiate the protocol with

the remote modem.

The following sections detail the operation of the #Ln command.

5.5.1 #L0 Command

The #L0 command, which is the factory default, allows a pair of modems to negotiate which V.42 mode (MNP

or LAP-M) will be used.

5.5.1.1

5.5.1.2

Originate Mode

If both modems have LAP-M capability, the modems will use LAP-M mode. If one or both

modems do not have LAP-M capability and both have MNP, the modems will use the MNP.

Answer Mode

The answering modem will respond to either an MNP Link Request or a LAP-M ODP signal,

depending on which is issued by the originating modem.

5.5.2 #L1 Command

The #L1 command enables MNP error correction and disables LAP-M. This command is for originate mode

only. Answer mode still accepts MNP or LAP-M.

5.5.3 #L2 Command

The #L2 command enables LAP-M error correction and disables MNP. This command is for originate mode

only. Answer mode still accepts MNP or LAP-M.

5.5.4 #L3 Command

In the previous commands, the modems use a two-phase process to establish a V.42 connection (“Detection”

to establish whether the remote modem is also error correcting, and “Protocol Establishment” to determine

parameters and establish the error correction connection). If you know that the other modem is a V.42 error-

correcting modem, and you wish to use LAP-M, use the #L3 command to disable the Detection phase and go

directly to Protocol Establishment. Both modems must have #L3 in effect.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.6 Modes of Operation

You can configure your MT2834MR6 in one of three different V.42 modes of operation, each with or without

compression. They are the non-error correction, reliable, and autoreliable modes. The modes and data

compression features are selected with commands described later in this chapter in “Compression, Error

Correction, Flow Control, Pass Through, and Pacing Commands.”

5.6.1 Non-Error Correction Mode (&E0)

In the non-error correction mode of operation, the MT2834MR6’s error correction capabilities are disabled,

and the modem functions as a non-error-correcting modem.

5.6.2 Reliable Mode (&E2)

In reliable mode, the MT2834MR6 uses its V.42 error correction capabilities during all transmissions. When

in reliable mode, the MT2834MR6 must be connected to a modem with a similar V.42 protocol activated

(MNP or LAPM). If the modems cannot establish a V.42 error correction connection, the MT2834MR6 will time

out and hang up.

5.6.3 Autoreliable Mode (&E1)

In autoreliable mode, the MT2834MR6 automatically determines, during the handshake at the start of the

online connection, whether or not the other modem is using error correction. If the MT2834MR6 determines

that the other modem is using V.42, it switches itself into the reliable (V.42) mode of operation. If it determines

that the other modem is not using V.42, the MT2834MR6 remains in non-error correction mode.

The MT2834MR6 uses a “Link Request” to determine whether the other modem is using V.42 error

correction. When the MT2834MR6 is in autoreliable mode and originates a call, it goes through normal

handshaking procedures. After establishing the online connection, the MT2834MR6 transmits a Link Request

message to the answering modem. If the answering modem replies with an appropriate V.42

acknowledgment response, the MT2834MR6 switches into reliable mode. Otherwise, it remains in non-error

correction mode. This V.42 handshake procedure generally takes about five seconds.

When operating in V.42 reliable mode, the MT2834MR6 stores data in a buffer as it is received. During

periods of error-caused retranmissions or compression slowdowns, this buffer may fill up. To prevent buffer

overflow and subsequent loss of data, the modem uses flow control to signal the computer attached to its RS-

232 port that the modem buffer is close to being full. This causes the computer to pause in its data

transmission until the modem is able to empty its buffer sufficiently to accept more data, at which time the

modem signals the computer that it may resume transmission.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.7 Flow Control

Flow control refers to the techniques used by computer devices to stop and restart the flow of data from each

other. Flow control is necessary so that a device does not receive more data than it can handle. In the case of

the MT2834MR6, there is a need for flow control in both directions. Flow control for data passing from your

computer to the modem is called modem-initiated flow control, and flow control for data passing from the

modem to your computer is called computer/terminal-initiated pacing (see Figure 5-1).

The MT2834MR6 supports both hardware and software modem-initiated flow control and computer/terminal-

initiated pacing. It also supports Hewlett Packard ENQ/ACK pacing. The MT2834MR6 can allow hardware

and software pacing to be passed through the modem to the other end of the link so that your computer or

terminal can control data start/stop activity through your modem. This is called “XON/XOFF pass-through".

To put it simply, flow control is something the modem does to the computer, while pacing is something the

computer does to the modem.

Figure 5-1. Flow control and pacing

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.8 Modem-Initiated Flow Control

When operating in V.42 reliable mode, the MT2834MR6 stores data in a buffer as it is received. During

periods of error-caused retransmissions or compression slowdowns, this buffer may fill up. To prevent buffer

overflow and subsequent loss of data, the modem uses flow control to signal the computer attached to its RS-

232 port that the modem buffer is close to being full. This causes the computer to pause in its data

transmission until the modem is able to empty its buffer sufficiently to accept more data, at which time the

modem signals the computer that it may resume transmission.

The MT2834MR6 can use either of two methods of modem-initiated flow control: software flow control, which

uses special XON and XOFF characters in the data transmissions, and hardware flow control, which uses the

CTS output on the RS-232 interface. Most terminals and computers support one or both of these methods.

5.8.1 XON/XOFF Flow Control (&E5)

In this method, control characters known as XON and XOFF are inserted by the modem into the flow of data

from the serial port. XOFF (CTRL-S), stops the flow of data, and XON (CTRL-Q), restarts it. XOFF/XON flow

control is not recommended for binary data, because an XOFF character could be part of the data, and would

halt data flow.

5.8.2 Hardware Flow Control (&E4)

With hardware flow control, the modem uses the RS-232 interface to control the flow of data on the serial port.

The CTS (Clear to Send) signal on Pin 5 of the RS-232 interface is brought low to stop the flow of data, and is

brought high to restart it.

When you select hardware flow control as your flow control method, you select it also for pacing. The

difference between the two is that flow control uses the CTS output signal, while pacing uses the RTS input

signal.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.9 Pacing (&E13)

As mentioned earlier, the MT2834MR6 can initiate flow control by issuing XON/XOFF commands or by

toggling the CTS signal on the RS-232 interface. The modem can also be configured to react to similar

commands and signals from the computer or terminal to which it is connected by the RS-232 interface.

Pacing is computer-initiated flow control. When pacing is enabled on the modem, the modem responds to the

terminal or computer pacing. When pacing is disabled on the modem, the modem ignores pacing.

Before you enable pacing on the MT2834MR6, you must select a flow control method. When pacing is

enabled, the MT2834MR6 responds either to XON/XOFF commands, or to the toggling of the RTS (Request

to Send) signal on Pin 4 of the RS-232 interface, depending on what you selected as your flow control

method.

5.9.1 XON/XOFF Pass-Through (&E7)

So far, you have had three choices to make regarding pacing. You can set the modem to respond to XON/

XOFF pacing, or to respond to RTS pacing, or you can set the modem to ignore pacing completely.

Another choice you can make (which actually can apply to both pacing and flow control, although it applies

mainly to pacing) is XON/XOFF pass-through. If your modem is set to respond to XON/XOFF commands, you

can have the modem do one of the following.

a. The modem responds to the XON and XOFF pacing commands while at the same time allowing

these commands to pass through the modem and on to the remote location. We call this

“respond, pass-through.”

b. The modem responds to XON/XOFF pacing, but does not allow the pacing signals to pass

through the modem and on to the remote location. We call this “respond, no pass-through.”

When XON and XOFF commands are allowed to pass through the modem, the computer at the remote site

receives these commands, and depending on how it is configured, the computer may respond to them also.

5.9.2 Non-Error Correction Mode Flow Control (&E10 and &E11)

You can use XON/XOFF to control the flow of data between two MT2834MR6s that are connected in non-

error correction mode. Disable or enable this method of flow control by using the Non-Error Correction Mode

Flow Control commands. When the modems are connected in reliable mode, a different method of modem

flow control is used, and the commands for non-error correction mode flow control are ignored.

You must enable non-error correction mode flow control if you use speed conversion in non-error correction

mode.

5.9.3 Hewlett Packard ENQ/ACK Pacing (&E9)

If the MT2834MR6 is used with Hewlett Packard or similar equipment that employs ENQ/ACK pacing, you

can configure it to respond to the ENQ/ACK commands used by Hewlett Packard systems. Doing so does not

effect any other flow control or pacing already configured in the modem.

When the MT2834MR6 is configured for ENQ/ACK, the ENQ (Ctrl-E) and ACK (Ctrl-F) signals from the HP

equipment will be accepted and responded to according to the Hewlett Packard protocol.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.10 Compression, Error Correction, Flow Control,

and Pacing Commands

The MT2834MR6 has several commands that control error correction, data compression, and flow control:

5.10.1 V.42 Error Correction Modes

&E0

&E1

&E2

Non-auto correction mode (no error correction).

Autoreliable mode (factory default).

Reliable mode.

5.10.2 Modem-Initiated Flow Control

&E3

&E4

&E5

Disable flow control.

CTS/RTS hardware flow control (factory default).

XON/XOFF software flow control.

5.10.3 XON/XOFF Pass-Through

&E6

Respond to and discard XON/XOFF characters when &E5 is selected (factory

default).

&E7

Respond to and pass through XON/XOFF characters when &E5 is selected.

5.10.4 Hewlett Packard ENQ/ACK Pacing

&E8

&E9

Ignore ENQ/ACK pacing characters (factory default).

Respond to ENQ/ACK pacing characters.

5.10.5 Non-Error Correction Mode Flow Control

&E10 Non-error correction mode flow control off (factory default).

&E11 Non-error correction mode flow control on.

5.10.6 Pacing (Computer-Initiated Flow Control)

&E12 Pacing off.

&E13 Pacing on (factory default).

5.10.7 Data Compression

&E14 Data Compression disabled.

&E15 Data Compression enabled.*

* The factory default setting for data compression is enabled, but the modem will not compress data unless &E1

(autoreliable mode) or &E2 (reliable mode) is also selected.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.11 Result Codes

When the MT2834MR6 connects with another modem with error-correction or data compression enabled, its

CONNECT responses change to inform you of the type of connection. (See Appendix C for a complete list of

result codes.)

5.11.1 MNP Error Correction

If terse responses are enabled, an R is added to the numeric code. If verbose responses are enabled, the

word RELIABLE follows the CONNECT message.

5.11.2 LAP-M Error Correction

If terse responses are enabled, an L is added to the numeric code. If verbose responses are enabled, the

word LAPM follows the CONNECT message.

5.11.3 Data Compression

If terse responses are enabled, a C is added to the numeric code. If verbose responses are enabled, the

word COMPRESSED follows the CONNECT message.

5.12 Speed Conversion

Speed conversion allows the MT2834MR6 to communicate at one speed over the phone line, and at another

speed at the RS-232 interface. The speed (baud rate) of the RS-232 interface, in bits per second (bps) can be

fixed independently of the speed of the online transmissions.

Besides data compression, another popular application for speed conversion involves an autoanswer

MT2834MR6 connected to a computer that does not have autobauding capability. This means that the

computer must be set at a fixed baud rate, regardless of whether the modem is communicating over the

phone line at 300, 1200, 2400, 4800, 9600, 14,400, 19,200, 21,600, 24,000, 26,400, or 28,800 bps. In this

application, speed conversion allows the modem to match its speed to that of a calling modem, while at the

same time communicating with the attached computer through its RS-232 serial port at a fixed baud rate,

which can be preselected at 300, 1200, 2400, 4800, 9600, 19,200, 38,400, 57,600, or 115,200 bps.

The flow control and pacing methods used between the computer and the modem during speed conversion

are the same as those used with V.42 error correction. The two choices (XON/XOFF or RTS/CTS) are

selected by using the &E commands detailed earlier in this chapter. If you are not using the modem’s V.42

error correction, you must activate modem flow control with a separate command (&E11), as explained

earlier.

There are three commands that relate specifically to speed conversion. They are the Baud Adjust ($BA),

Modem Baud Rate ($MB) and Serial Port Baud Rate ($SB) commands.

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.12.1 Baud Adjust ($BA)

In typical operations, the MT2834MR6 will do one of two things regarding speed. It will automatically match

the speed of its RS-232 interface and phone line transmissions to that of the terminal or computer to which it

is connected as soon as it receives its first AT command. Or, in autoanswer mode, it will match its RS-232

and transmission speeds to that of the originating modem that called it. This is typical of many dial-up

modems, and it is referred to variously as auto-speed or baud adjust. Multi-Tech uses the term baud adjust.

When you enable speed conversion, the modem does not adjust its speed at the RS-232 serial port, even if

the modem does adjust its line transmission speed. To turn baud adjust off and speed conversion on, type

AT$BA0 (where the 0 is a zero).

Note: Even though baud adjust sounds like it should mean the same thing as speed conversion, it actually

means the opposite.

a. Turning baud adjust off turns speed conversion on.

b. Turning baud adjust on turns speed conversion off.

To turn baud adjust on and speed conversion off, type AT$BA1 and press ENTER. The modem will now

match its RS-232 speed to that of the computer, and will adjust its speed to any changes in the computer’s

speed in the originate mode, or to the speed of the originating modem when it’s in the answer mode. With

baud adjust on, the speed at which the modem communicates over the phone line is always the same as the

speed at which it communicates via its RS-232 serial port.

5.12.2 Modem Baud Rate ($MB)

The $MB command presets the MT2834MR6’s transmission rate for originate operations, i.e., the speed of

the modem’s transmissions over the telephone lines when originating a call. With speed conversion, this

transmission speed can be a different rate than the serial port speed.

When the MT2834MR6 receives a call from another modem, it automatically switches its phone line

transmission rate to match the calling modem. However, if the MT2834MR6 originates a call to another

modem that is unable to connect at the speed of the MT2834MR6, the MT2834MR6 will automatically drop to

a lower speed in an attempt to match the speed of that modem. For example, if the MT2834MR6 is set for

28,800 bps and calls another modem that has a top speed of 9600 bps, it will drop to 9600 bps.

When baud adjust is on ($BA1), speed conversion is off, as we discussed earlier. In that case, the $MB

command is ignored, since it is part of speed conversion.

To set the Modem Baud Rate, type AT$MBn, where n is the desired rate.

AT$MB75

ITU-T V.23

1200 bps

4800 bps

14,400 bps

19,200 bps

33,600 bps (factory default)

AT$MB300

AT$MB2400

AT$MB9600

AT$MB16800 16,800 bps

AT$MB28800 28,800 bps

300 bps

2400 bps

9600 bps

AT$MB1200

AT$MB4800

AT$MB14400

AT$MB19200

AT$MB33600

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.12.3 Serial Port Baud Rate ($SB)

The $SB command presets the speed of the MT2834MR6’s RS-232 serial port in both the originate and the

answer modes. Speed conversion allows you to set this serial port baud rate at a fixed speed of up to

115,200 bps, regardless of the modem’s transmission speed setting.It also sets the default speed at which

the modem issues command responses (result codes).

For this command to work, the modem’s baud adjust feature must be turned off with the $BA command.

The MT2834MR6 will accept AT commands at any speed, regardless of the speed preset by the $SB

command. If the modem receives such a command at a speed that is different from the preset speed, the

modem switches its serial port baud rate to match the new AT command speed, although the baud rate value

stored by the $SB command remains the same. This provides you with a convenient way to switch the serial

port speed, while still making it easy to automatically return to the original speed the next time the modem is

powered up, or reset using the ATZ command.

To set the serial port baud rate, type AT$SBn, where n can be 300, 1200, 2400, 4800, 9600,19,200, 38,400,

57,600, or 115,200 bps as listed below:

AT$SB300

300 bps

AT$SB1200

AT$SB4800

AT$SB19200

AT$SB57600

1200 bps

4800 bps

19200 bps

57,600 bps

AT$SB2400

AT$SB9600

AT$SB38400

2400 bps

9600 bps

38400 bps

AT$SB115200 115,200 bps (factory default)

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.13 Related Commands

5.13.1 Autoreliable Buffering ($A)

In autoreliable mode, the modem is given four seconds to establish a reliable connection. If it cannot

establish a reliable connection in that time, the modem drops to non-error correction mode. Any data

received during this period is normally discarded. The $A command is used to cause the modem to buffer

(save) data that is received during the autoreliable time-out period. This data is then output by the modem

after it sends the CONNECT message.

Type AT$A0 to discard data received during the autoreliable time period (factory default).

Type AT$A1 to buffer data received during the autoreliable time period.

5.13.2 Maximum Block Size (&BS)

The maximum size of reliable mode data blocks is controlled by the &BS command. MNP Class 3 sends

blocks of 1 to 64 characters. MNP Classes 4 and 5 normally send blocks of 1 to 256 characters. Reducing the

block size for Classes 4 and 5 to 64 characters may give a smoother flow of data, and improve throughput

performance on noisy phone lines. Using smaller block sizes over good phone lines may cause a slight loss

in data throughput.

Type AT&BS0 for a maximum transmit block size of 64 characters.

Type AT&BS1 for a maximum transmit block size of 256 characters (factory default).

5.13.3 Autoreliable Fallback Character ($F)

In autoreliable mode, the modem is given four seconds to establish a reliable connection. If a single carriage

return character, <CR>, is received from the remote modem during this four second period, the autoreliable

modem assumes that the remote modem is not in reliable mode and drops to a non-error correction mode.

The carriage return character is then output following the CONNECT message. The carriage return character

is the only character that causes the modem to drop to non-error correction mode. Any other data is either

buffered or discarded.

Use the $F command to disable this fallback feature. The autoreliable fallback character ($F) and the auto

reliable buffering ($A) commands can be used together to cause the modem to buffer all data received up to

the carriage return and then drop to non-error correction mode. All data received will then be output following

the CONNECT message.

Type AT$F0 to cause the modem not to fall back to non-error correction mode if a carriage return character is

received.

Type AT$F1 to cause the modem to fall back to error correction mode if a carriage return character is

received (factory default).

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Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.13.4 Retransmit Count ($R)

If errors are received during a reliable connection, the modem resends the block of data that contained

errors. If another error occurs, the block is re-sent again. The modem counts the number of times that a data

block is re-sent. If the same block of data is re-sent 12 times and still has not been received properly, the

modem aborts the connection, as dictated by the AT$R0 command.

This retransmit counter can be disabled with the $R1 command. When the retransmit counter is disabled, the

modem keeps trying to send data and will not abort, not matter how many times the same block is re-sent.

Type AT$R0 to disconnect if the retransmit count is exceeded (factory default).

Type AT$R1 to not disconnect because of excessive retransmits.

5.13.5 V.42 Error Correction at 300 bps ($E)

At 300 bps, error correction is not normally used. $E1 lets the MT2834MR6 function in either non-error

correction (&E0), autoreliable (&E1) or reliable (&E2) mode at 300 bps. $E0, which is the factory default

setting, disables V.42 error correction at 300 bps altogether.

5.14 Summary

V.42 error correction is built into the MT2834MR6’s hardware, and detects virtually 100 percent of

transmission errors, which are usually caused by noisy phone lines. When errors are detected, the V.42

protocol causes the modem to retransmit the errant data block.

V.42bis and MNP data compression, also built into the MT2834MR6’s hardware, provides an effective

throughput higher than the modem’s transmission speed. The amount of increase depends on the type of

data being transmitted.

The MNP protocol is divided into several classes, which for our purposes are numbered 3 through 5. The

MT2834MR6 uses all of these MNP classes, which yields higher throughput and error-free transmissions.

LAP-M provides another type of error correction.

The MT2834MR6 can be set for three different modes of operation. Non-error correction mode disables error

correction, reliable mode enables it, and autoreliable mode allows the modem to automatically turn V.42 on

when it detects its use in another modem.

Flow control methods are used by the MT2834MR6 to prevent data loss from buffer overflow. The modem can

both initiate it (flow control) and respond to it (pacing), using either XON/XOFF commands or RS-232

signaling via the serial port’s CTS and RTS signals. Hewlett Packard ENQ/ACK pacing is also supported. If

needed, XON/XOFF commands can be “passed through” the modem to a remote computer or terminal.

Speed conversion allows the MT2834MR6 to operate at one speed over the telephone lines and another

speed at the RS-232 serial port, allowing the computer or terminal to communicate with the modem at a fixed

speed of up to 115,200 bps, while the modem operates at various speeds up to 33,600 bps. This ability is for

data compression, since your terminal or computer must present data to the modem at a higher speed than

the modem sends it over the phone line.

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Chapter 6 - Testing & Troubleshooting

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Chapter 6 - Testing and Troubleshooting

6.1 Introduction

Each time you power up the MT2834MR6, it performs an automatic self-test to ensure proper operation. The

MT2834MR6 also has three diagnostic tests: local analog loopback, digital loopback (remote/automatic), and

digital loopback (local/manual). These ITU-T V.54 loopback tests isolate telephone circuit and transmission

problems.

In a loopback test, data from your computer loops through the circuits of your modem and/or a remote modem

before it appears on your monitor. When the loop has been completed, the data on your PC’s monitor should

match the original data.

The local analog loopback test allows you to verify that the modem’s transmitter and receiver circuits are

functioning properly.

The local digital loopback allows you to verify that the local computer or terminal, the two modems, and the

transmission line between them are functioning properly.

The remote digital loopback test allows you to verify that the remote computer or terminal, the remote modem,

the serial ports, the telephone line, and the local modem are functioning properly.

Note: Loopback tests operate at all speeds except 300 bps.

Other tests are initiated with the MultiModemManager software, as explained in the MultiModemManager

Owner's Manual.

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Chapter 6 - Testing and Troubleshooting

6.2 Local Analog Loopback Test (V.54 Loop 3)

In this test, data from your computer or terminal is sent to your modem’s transmitter, converted into analog

form, looped back to the modem’s receiver, converted into digital form, and then sent to your monitor for

verification. No connection to the phone line is required. See Figure 6-1.

Figure 6-1. Local analog loopback test.

6.2.1 Test Procedure

1. Connect the modem to your computer. Using your communication software, set the desired baud rate.

2. Type ATU or ATU0 and press ENTER. This places your modem in analog loopback mode in the

originate mode. A CONNECT message should appear on your display. The modem is now out of

command mode and in a pseudo-online mode.

3. Note that the CD LED is on. If you’re set for 14,400 bps or higher, the Speed LED should be on. If the CD

LED is not on, there is a defect in your modem.

4. Enter characters from your keyboard. For this test, typing multiple uppercase U characters is a good way

to send an alternating test pattern of binary ones and zeros. The characters entered should be displayed

on your monitor. The TD and RD LEDs should flash when a character is entered.

5. For a more complete test, you should also test the modem in answer mode. To do this, you must first

terminate the originate mode by entering an escape sequence (+++AT<CR> or <BREAK>AT<CR>). An

OK should appear on your display. Then type ATU1 and press ENTER to place the modem in analog

loopback in answer mode.

6. Note that the CD LED is on. If you’re set for 14,400 bps or higher, the Speed LED should be on. If the CD

LED is not on, there is a defect in your modem.

7. Enter characters from your keyboard. Type multiple uppercase U characters to send an alternating test

pattern of binary ones and zeros. The characters entered should be displayed on your monitor. The TD

and RD LEDs should flash when a character is entered.

8. To exit the test, enter an escape sequence (+++AT<CR> or <BREAK>AT<CR>), which returns the

modem to command mode.

9. Your modem passes this test if the data received on your monitor are the same as the data entered from

your keyboard. If different data appear on your monitor, your modem is probably causing the problem,

though it could also be your computer. If your modem passes this test, but you are receiving errors while

on line, the remote modem or the phone line could be at fault.

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Chapter 6 - Testing and Troubleshooting

6.3 Remote Digital Loopback Test (V.54 Loop 2)

In this test, your modem must be online with another modem, such as another ZDX, that is set up to respond

to a request for remote digital loopback. With the ZDX, this ability to respond is controlled by the &T

command. AT&T4 enables the response to remote digital loopback; AT&T5 disables the response. The

modem defaults to &T5 on power-up, so this must be changed on the remote modem before initiating remote

digital loopback.

Initiate remote digital loopback with the ATU2 command, which places the remote modem in digital loopback

mode. Data from your computer or terminal are transmitted through your modem and over the phone line to

the remote modem, where they are then looped back to your modem. See Figure 6-2.

Figure 6-2. Remote digital loopback test.

6.3.1 Test Procedure

1. Arrange to have &T4 set on the remote test modem.

2. Open your communications software and go into terminal mode. Type AT and press ENTER; you should

get an OK message. Type AT&E0<CR> to disable error correction.

3. Dial the remote modem and establish your online connection.

4. Type the escape sequence (+++AT<CR> or <BREAK>AT<CR>) to bring your modem into command

mode while maintaining the connection with the remote modem.

5. Type ATU2 and press ENTER. The local modem responds to this command by transmitting an

unscrambled marking signal, which causes the remote modem to place itself in digital loopback mode.

Then the local modem exits command mode and enters online mode.

6. Enter data from your keyboard. For this test, typing multiple uppercase U characters is a good way to

send an alternating test pattern of binary ones and zeroes. Data received by the remote modem enters

its analog receiver, is converted to digital data, is reconverted into analog, and then is transmitted back to

your modem. Your modem passes this test if the data received on your monitor is the same as the data

entered from your keyboard.

7. To exit the test, enter an escape sequence (+++AT<CR> or <BREAK>AT<CR>), which returns the

modem to command mode. The modem should respond with an OK message. If you wish to stay on line

with the remote modem for normal data transmission, type ATO and press ENTER. If you wish to

terminate the call, type ATH and press ENTER to hang up.

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Chapter 6 - Testing and Troubleshooting

6.4 Local Digital Loopback Test (V.54 Loop 2)

This test is identical to the remote digital loopback test with one exception. Instead of using your modem to

signal a remote modem to place itself in digital loopback mode, your modem is placed in digital loopback

mode while the remote modem is not. Data is entered and transmitted from the remote modem, sent across

the phone line to the local modem, and looped back to the remote modem. See Figure 6-3.

Figure 6-3. Local digital loopback test

6.4.1 Test Procedure

1. Open your communications software and go into terminal mode. Type AT and press ENTER; you should

get an OK message. Enter AT&E0<CR> to disable error correction.

2. Dial the remote modem and establish your online connection.

3. Type an escape sequence (+++AT<CR> or <BREAK>AT<CR>) to bring your modem into command

mode while still maintaining the connection with the remote modem.

4. Type ATU3 and press ENTER. Once you receive an OK message from your modem (if responses are

enabled), your modem is placed in digital loopback mode.

5. Have someone enter data from the remote keyboard. For this test, typing multiple uppercase U

characters is a good way to send an alternating test pattern of binary ones and zeros. The data received

by your modem enters its analog receiver, is converted to digital data, is reconverted into analog, and

then is transmitted back to the remote modem. Your modem passes this test if the data received on the

remote monitor is the same as the data entered from the remote keyboard.

6. To exit the test, enter an escape sequence (+++AT<CR> or <BREAK>AT<CR>), which returns the

modem to command mode. The modem should respond with an OK message. If you wish to stay on line

with the remote modem for normal data transmission, type ATO and press ENTER. If you wish to

terminate the call, type ATH and press ENTER to hang up.

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Chapter 7 - Warranty & Service

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Chapter 7 - Warranty And Service

7.1 Multi-Tech Systems, Inc. Warranty & Repairs Policies

7.1.1 Warranty

Multi-Tech Systems, Inc., (hereafter “MTS”) warrants that its products will be free from defects in material or

workmanship for a period of two, five, or ten years (depending on model) from date of purchase, or if proof of

purchase is not provided, two, five, or ten years (depending on model) from date of shipment.

MTS MAKES NO OTHER WARRANTY, EXPRESS OR IMPLIED, AND ALL IMPLIED WARRANTIES OF

MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED.

This warranty does not apply to any products which have been damaged by lightning storms, water, or power

surges or which have been neglected, altered, abused, used for a purpose other than the one for which they

were manufactured, repaired by Customer or any party without MTS’s written authorization, or used in any

manner inconsistent with MTS’s instructions.

MTS’s entire obligation under this warranty shall be limited (at MTS’s option) to repair or replacement of any

products which prove to be defective within the warranty period or, at MTS’s option, issuance of a refund of

the purchase price. Defective products must be returned by Customer to MTS’s factory – transportation

prepaid.

MTS WILL NOT BE LIABLE FOR CONSEQUENTIAL DAMAGES, AND UNDER NO CIRCUMSTANCES WILL

ITS LIABILITY EXCEED THE PRICE FOR DEFECTIVE PRODUCTS.

7.1.2 U.S. and Canadian Customers

In the event that service is required, products may be shipped, freight prepaid, to our Mounds View,

Minnesota, factory:

Multi-Tech Systems, Inc.

2205 Woodale Drive

Mounds View, MN 55112

Attn: Repairs, Serial #______

A Returned Materials Authorization (RMA) is not required. Return shipping charges (surface) will be paid by

MTS. Please include inside the shipping box a description of the problem, a return shipping address (must

have street address, not P.O. Box), a telephone number, and if the product is out of warranty, a check or

purchase order for repair charges.

For out of warranty repair charges, go to: www.multitech.com. Extended two-year overnight replacement

agreements are available for selected products. Please call MTS at 888 288-5470, extension 5308, or visit

our web site at www.multitech.com for details on rates and coverages.

Please direct your questions regarding technical matters, product configuration, verification that the product

is defective, etc., to our Technical Support department at 800 972-2439 or e-mail [email protected].

Please direct your questions regarding repair expediting, receiving, shipping, billing, etc., to our Repair

Accounting department at 800 328-9717 or +763 785-3500, or e-mail [email protected].

Repairs for damages caused by lightning storms, water, power surges, incorrect installation, physical abuse,

or user-caused damages are billed on a time-plus-materials basis.

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Chapter 7 - Warranty And Service

7.1.3 International Customers (outside U.S.A. and Canada)

Your original point of purchase reseller may offer the quickest and most economical repair option for your

Multi-Tech product. You may also contact any Multi-Tech sales office for information about the nearest

distributor or other repair service for your Multi-Tech product: www.multitech.com.

In the event that factory service is required, products may be shipped, freight prepaid, to our Mounds View,

Minnesota, factory. Recommended international shipment methods are via Federal Express, UPS or DHL

courier services, or by airmail parcel post; shipments made by any other method will be refused. A Returned

Materials Authorization (RMA) is required for products shipped from outside the U.S.A. and Canada. Please

Please include inside the shipping box a description of the problem, a return shipping address (must have

street address, not P.O. Box), your telephone number, and if the product is out of warranty, a check drawn on

a U.S. bank or your company’s purchase order for repair charges. Repaired units will be shipped freight

collect, unless other arrangements are made in advance.

Please direct questions regarding technical matters, product configuration, verification that the product is

defective, etc., to our Technical Support department nearest you, as listed at http://www.multitech.com/

COMPANY/offices/DEFAULT.ASP., or e-mail [email protected]. When calling the U.S., please direct

questions regarding repair expediting, receiving, shipping, billing, etc., to our Repair Accounting department

at +763 717-5631 in the U.S.A., or e-mail [email protected].

Repairs for damages caused by lightning storms, water, power surges, incorrect installation, physical abuse,

or user-caused damages are billed on a time-plus-materials basis.

7.1.4 InternationalDistributors

Procedures for international distributors of Multi-Tech products are on the Distributor Web site at http://

www.multitech.com/PARTNERS/login/.

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Chapter 7 - Warranty And Service

7.2 Repairs

7.2.1 Repair Procedures for U.S. and Canadian Customers

In the event that service is required, products may be shipped, freight prepaid, to our Mounds View,

Minnesota factory:

Multi-Tech Systems, Inc.

2205 Woodale Drive

Mounds View, MN 55112

Attn: Repairs, Serial # ____________

A Returned Materials Authorization (RMA) is not required. Return shipping charges (surface) will be paid by

MTS. Please include, inside the shipping box, a description of the problem, a return shipping address (must

have street address, not P.O. Box), your telephone number, and if the product is out of warranty, a check or

purchase order for repair charges. For out of warranty repair charges, go to www.multitech.com

Extended two-year overnight replacement service agreements are available for selected products. Please

call MTS at (888) 288-5470, extension 5308 or visit our web site at: www.multitech.com for details on rates

and coverages.

Please direct your questions regarding technical matters, product configuration, verification that the product

is defective, etc., to our Technical Support department at (800) 972-2439 or email [email protected].

Please direct your questions regarding repair expediting, receiving, shipping, billing, etc., to our Repair

Accounting department at (800) 328-9717 or (763) 717-5631, or email [email protected].

Repairs for damages caused by lightning storms, water, power surges, incorrect installation, physical abuse,

or user-caused damages are billed on a time-plus-materials basis.

7.2.2 Repair Procedures for International Customers

Your original point of purchase Reseller may offer the quickest and most economical repair option for your

Multi-Tech product. You may also contact any Multi-Tech sales office for information about the nearest

distributor or other repair service for your Multi-Tech product. Visit our website at: www.multitech.com

In the event that factory service is required, products may be shipped, freight prepaid to our Mounds View,

Minnesota factory. Recommended international shipment methods are via Federal Express, UPS or DHL

courier services, or by airmail parcel post; shipments made by any other method will be refused. A Returned

Materials Authorization (RMA) is required for products shipped from outside the U.S.A. and Canada. Please

Please include, inside the shipping box, a description of the problem, a return shipping address (must have

street address, not P.O. Box), your telephone number, and if the product is out of warranty, a check drawn on

a U.S. bank or your company’s purchase order for repair charges. Repaired units shall be shipped freight

collect, unless other arrangements are made in advance.

Please direct your questions regarding technical matters, product configuration, verification that the product

is defective, etc., to our Technical Support department nearest you or email [email protected]. When

calling the U.S., please direct your questions regarding repair expediting, receiving, shipping, billing, etc., to

our Repair Accounting department at: +(763) 717-5631 in the U.S.A., or email [email protected].

Repairs for damages caused by lightning storms, water, power surges, incorrect installation, physical abuse,

or user-caused damages are billed on a time-plus-materials basis.

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Chapter 7 - Warranty And Service

7.2.3 Repair Procedures for International Distributors

Procedures for International Distributors of Multi-Tech products are on the distributor web site:

www.multitech.com

7.2.4 Replacement Parts

SupplyNet, Inc., can supply you with replacement power supplies, cables and connectors for selected Multi-

Tech products. You can place an order with SupplyNet via mail, phone, fax or the Internet at the following

addresses:

Mail:

SupplyNet, Inc.

614 Corporate Way

Valley Cottage, NY 10989

Phone: 800 826-0279

Fax: 914 267-2420

Email: [email protected]

Internet: http://www.thesupplynet.com

7.3 Technical Support

Multi-Tech Systems has an excellent staff of technical support personnel available to help you get the most

out of your Multi-Tech product. If you have any questions about the operation of this unit, please call 800 972-

2439 (USA and Canada) or 763 785-3500 (international and local). Please have modem information

available. You can also contact Technical Support by e-mail at the following addresses:

Country

Telephone

U.S.A., Canada

France:

India:

U.K.:

Rest of world:

[email protected]

800 972-2439

+(33) 1-64 61 09 81

+91 (124) 6340778

+(44) 118 959 7774

+763 717-5863

Please note the status of the modem before contacting Technical Support. Status information can include the

state of the LED indicators, screen messages, diagnostic test results, problems with a specific application,

etc.

7.4 Internet Site

Multi-Tech is a commercial provider on the Internet. Multi-Tech has a Web site at: www.multitech.com.

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Appendices

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Appendix

Appendix A

ASCII Conversion Chart

CTRL CODE HEX DEC CODE HEX DEC CODE HEX DEC CODE HEX DEC

NUL

SOH

STX

ETX

EOT

ENQ

ACK

BEL

0A 10

0B 11

0C 12

0D 13

0E 14

0F 15

10 16

11 17

12 18

13 19

14 20

15 21

16 22

17 23

18 24

19 25

1A 26

1B 27

1C 28

1D 29

1E 30

1F 31

(

)

20 32

21 33

22 34

23 35

24 36

25 37

26 38

27 39

28 40

29 41

2A 42

2B 43

2C 44

2D 45

2E 46

2F 47

30 48

31 49

32 50

33 51

34 52

35 53

36 54

37 55

38 56

39 57

3A 58

3B 59

3C 60

3D 61

3E 62

3F 63

40 64

41 65

42 66

43 67

44 68

45 69

46 70

47 71

48 72

49 73

4A 74

4B 75

4C 76

4D 77

4E 78

4F 79

50 80

51 81

52 82

53 83

54 84

55 85

56 86

57 87

58 88

59 89

5A 90

5B 91

5C 92

5D 93

5E 94

5F 95

64 100

65 101

66 102

67 103

68 104

69 105

6A 106

6B 107

6C 108

6D 109

6E 110

6F 111

70 112

71 113

72 114

73 115

74 116

75 117

76 118

77 119

78 120

79 121

7A 122

7B 123

7C 124

7D 125

7E 126

[

DLE

DC1

DC2

DC3

DC4

NAK

SYN

ETB

CAN

SUB

ESC

{

}

;

]

DEL 7F 127

NUL

SOH

STX

ETX

EOT

ENQ

ACK

BEL

Null, or all zeros

StartofHeader

StartofText

EndofText

EndofTransmission

Enquiry

Acknowledge

Bell or Alarm

Backspace

Horizontal Tab

LineFeed

VerticalTab

Form Feed

CarriageReturn

ShiftOut

ShiftIn

DataLinkEscape

Device Control 1

Device Control 2

Device Control 3

Device Control 4

SYN

ETB

CAN

SUB

ESC

DEL

Sync.

EndTransmissionBlock

Cancel

EndofMedium

Substitute

DLE

DC1

DC2

DC3

DC4

NAK

Escape

FileSeparator

GroupSeparator

RecordSeparator

UnitSeparator

Delete

NegativeAcknowledge

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Appendix

Appendix B

Dial Pulses

When you pulse dial, as when you make a call with a rotary dial telephone, your telephone or modem

generates codes in the form of pulses that simulate the opening and closing of old-fashioned electric relays,

or switches. The number of pulses in a code are the same as the digit they encode; thus, the digit 1 is

represented by one pulse, the digit 2 by two pulses, etc. In Figure B-1, the digit 2 is pulse dialed, followed by

the digit 1. Each pulse consists of an A ms open (break) and a B ms closed (make), where A is either 60 or 67

ms, and B is either 40 or 33 ms, for a total of 100 ms per cycle, or a rate of 10 pulses per second. The

interdigital pause time is 800 ms. The pulse ratios are controlled by the &P command.

Figure B-1. Dial pulses

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Appendix

Tone Dial Frequencies

The tone dialing method combines two frequencies for each of the twelve digits found on a touch-tone dial

pad. This method is referred to as dual-tone multi-frequency (DTMF) dialing.

The four horizontal rows on a touch-tone keypad use four low-frequency tones (697, 770, 852, 941 Hz), while

the three vertical columns use three high-frequency tones (1209, 1336, 1477 Hz). The tone frequency

tolerance is ± 0.02%.

For example, the digit 4 is dialed by combining two tone frequencies: 770 Hz from the second row, and 1209

Hz from the first column. In another example, the digit 9 is dialed with tone frequencies 852 Hz and 1477 Hz.

Figure B-2. Standard DTMF frequencies

Figure B-3. Extended DTMF frequencies

The extended DTMF characters (A, B, C, D) are the high-end frequencies (1633 Hz) defined on some

telephone sets with a fourth vertical column of buttons. This fourth column provides for extended PBX control

functions. The actual functions that are provided depend on the PBX manufacturer’s implementation and

feature set.

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Appendix

Appendix C

Result Code Summary

Multi-TechResultCodes(&Q0)

Terse

Verbose

Definition

Command was executed without error; ready for next command.

Modem has detected carrier and gone online.

Modem has detected ring caused by incoming call.

No carrier signal has been detected within the allowed time.

Error in command line (too many, or invalid characters).

Modem has detected carrier at 1200 bps and gone online.

No dial tone has been detected.

CONNECT

RING

NO CARRIER

ERROR

CONNECT 1200

NO DIALTONE

BUSY

A busy signal has been detected.

NO ANSWER

CONNECT 2400

The remote system did not answer.

Modem has detected carrier at 2400 bps and gone online.

Not used.

CONNECT 4800

CONNECT 9600

CONNECT 14400

CONNECT 19200

CONNECT 21600

CONNECT 1275

Modem has detected carrier at 4800 bps and gone online.

Modem has detected carrier at 9600 bps and gone online.

Modem has detected carrier at 14400 bps and gone online.

Modem has detected carrier at 19200 bps and gone online.

Modem has detected carrier at 21600 bps and gone online.

Modem is connected in V.23 mode.

CONNECT 24000

CONNECT 26400

CONNECT 28800

CONNECT 31200

CONNECT 33600

Modem has detected carrier at 24000 bps and gone online.

Modem has detected carrier at 26400 bps and gone online.

Modem has detected carrier at 28800 bps and gone online.

Modem has detected carrier at 31200 bps and gone online.

Modem has detected carrier at 33600 bps and gone online.

MNP Reliable Mode. If the modem connects using MNP error correction, the word RELIABLE or the letter R is added to

the CONNECT responses as follows:

CONNECT RELIABLE

CONNECT 1200 RELIABLE

CONNECT 2400 RELIABLE

CONNECT 4800 RELIABLE

CONNECT 9600 RELIABLE

CONNECT 14400 RELIABLE

CONNECT 19200 RELIABLE

CONNECT 21600 RELIABLE

CONNECT 24000 RELIABLE

CONNECT 26400 RELIABLE

CONNECT 28800 RELIABLE

CONNECT 31200 RELIABLE

CONNECT 33600 RELIABLE

11R

12R

13R

19R

21R

24R

26R

28R

31R

33R

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Appendix

LAP-M Reliable Mode. If the modem connects using LAP-M error correction, the word LAPM or letter L is added to the

CONNECT responses as follows:

CONNECT LAPM

CONNECT 1200 LAPM

CONNECT 2400 LAPM

CONNECT 4800 LAPM

CONNECT 9600 LAPM

CONNECT 14400 LAPM

CONNECT 19200 LAPM

CONNECT 21600 LAPM

CONNECT 24000 LAPM

CONNECT 26400 LAPM

CONNECT 28800 LAPM

CONNECT 31200 LAPM

CONNECT 33600 LAPM

10L

12L

13L

19L

21L

24L

26L

28L

31L

33L

Data Compression. If the modem connects using data compression, the word COMPRESSED or the letter C is added to

the CONNECT responses.

Standard AT Result Codes (&Q1)

If standard AT command set responses are selected by the &Q command, the following result codes change:

Not used.

CONNECT 2400

Modem has detected carrier at 2400 bps and gone online.

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Appendix

Appendix D

S-Register Summary

Unit

Range

Default

Description

1 ring 0, 1–255

Sets the number of rings until the modem answers.

ATS0=0 disables auto answer completely.

1 ring 0–255

decimal 0–127

Counts the rings that have occurred.

43 (+)

13 (^M)

10 (^J)

8 (^H)

Sets ASCII code for the escape code character.

Sets ASCII code for the RETURN character.

Sets ASCII code for the LINE FEED character.

Sets ASCII code for the BACKSPACE character.

1 sec

2–255

4–255†

4–7‡

4†

4‡

Time the modem waits for a dial tone before aborting a call.

Time the modem waits for a carrier signal before aborting a call.

Length of the pause by a comma character in a dialing command.

1–255

1–45*

1–55‡

45*

55‡

0–255

4–255†

4–7‡

4†

4‡

100 ms 1–255

Sets delay between when the modem detects a valid carrier

signal and when it turns on its CD circuit.

S10

100 ms 1–254,

255

Sets how long a carrier signal must be lost before the modem

disconnects. S10=255 causes the modem to not disconnect with

loss of carrier.

S11

1 ms

1–255

80-255* 80*

80-255‡ 80‡

Sets spacing and duration of dialing tones. 50 ms is the

recommended minimum.

S13

S17

S24

S25

S30

decimal 0, 1–127 37 (%)

Sets ASCII code for remote configuration escape character.

S13=0 disables remote configuration.

10 ms 1–255

50 ms 0–255

100 ms 0, 1–255

1 min. 0, 1–255

Sets the length of the break time (space) sent to the local PC

when the modem receives a remote break.

Sets the time the DSR, CTS, and CD signals drop before going

high again. Used for some PBX and CBX phone systems.

Sets the time the DTR signal must be dropped before the modem

dis-connects. The 0 default equals 50 ms.

Sets how long the modem waits after the last character is

received or transmitted before it disconnects. The 0 default

disables the timer.

S32

100 ms 0–255

Sets the time the modem will wait for a RETURN to be entered

during escape sequence execution.

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Appendix

S34

S36

1 char- 0–60

acter

Sets the number of command characters allowed after +++AT.

1 sec

0, 1-255

Sets the time between DTR inactive and modem off-hook.

S36=0 disables DTR busy-out.

S37

S43

1 sec

0-255

Sets the time between DTR active and modem on-hook.

Sets fixed V.34 connect speed.

decimal 33, 31,

28, 26,

28 = 28800 bps; 26 = 26400 bps;. . .

24, 21,

48 = 4800 bps. 0 default disables this feature.

19, 16,

14, 12,

96, or 48

decimal 33, 31,

28, 26,

S48

S94

Sets maximum V.34 connect speed.

33 = 33600 bps; 31 = 31200 bps;. . .

24, 21,

48 = 4800 bps. 0 default disables feature (same as S48=33).

19, 16,

14, 12,

96, or 48

1 sec

0–254,

255

Sets the maximum time the modem remains out of service when

*H1 is active. S94=255 causes the modem to remain out of

service indefinitely, until it receives an enable from the

management software.

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Appendix

Appendix E

AT Command Summary

Command Values

Description

n/a

Attention Code

The attention code precedes all command lines except A/, A: and escape codes.

RETURN

RETURN Key

Press the RETURN (ENTER) key to execute most commands.

Force Answer Mode

Answer call immediately without waiting for ring.

Repeat Last Command

Do not precede this command with AT. Do not press RETURN to execute.

Continuous Redial

Continuous redial of last number until answered. (10 redials in North American models.

Not used on International or U.K. models.)

&An

$An

#An

n = 0 or 1

n = 0–3

Answerback

*** &A0 Answerback off.

&A1 Answerback on.

Auto-Reliable Buffering

*** $A0

$A1

Discard data received during establishment of reliable connection

Buffer data received during establishment of reliable connection

Auto Speed Detection in Answer Mode

*** #A0

Start at maximum speed and fall back to 14400 to 12000 to 9600 to 4800 to

2400 to 1200 to 300 bps.

#A1

#A2

#A3

Maximum speed only.

Start at maximum speed and fall back incrementally to 4800 bps only.

Start at 2400 bps and fall back to 1200 to 300 bps only.

n = 0 or 1

Answer Tone (International models only)

*** B0

Select ITU-T V.21 answer tone.

Select Bell 103 answer tone.

&BSn

$BAn

Maximum Reliable Block Size

&BS0 Maximum transmit block size of 64 characters.

*** &BS1 Maximum transmit block size of 256 characters.

Baud Adjust

*** $BA0 Set baud adjust off, speed conversion on. (Serial port speed is independent of

modem data rate.)

$BA1 Set baud adjust on, speed conversion off. (Serial port speed is same as

modem data rate.)

&Cn

n = 0, 1, 2,

or 4

Carrier Detect Control

&C0 Force Carrier Detect on.

*** &C1 Let Carrier Detect follow carrier signal.

&C2 Let Carrier Detect drop for time set by S24 on disconnect, then go high again.

&C4 Reset modem when Carrier Detect drops.

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Appendix

&CDn

n = 0 or 1

Cleardown at Disconnect

*** &CD0 Enable cleardown.

&CD1 Disable cleardown.

s = phone #

Dial

Dial telephone number s, where s may include up to 60 digits or T, P, R, comma,

colon, and semicolon characters.

DsNd

&Dn

s = phone #

d = 0 or 1

Store Phone Number

To store, enter D followed by telephone number s, then N followed by directory

number d.

n = 0, 1, 2,

or 3

Data Terminal Ready Control

&D0 Modem ignores DTR signal.

&D1 When DTR drops, the modem hangs up. While DTR is low, the modem accepts

commands but will not dial or auto-answer until DTR goes high again.

*** &D2 Same as &D1.

&D3 When DTR drops, the modem hangs up and resets as if an ATZ or an AT&F

command was issued.

%DCn

%DFn

%DPn

>DTn

n = 0 or 1

Command Mode Control

*** %DC0 Enable command mode.

%DC1 Disable command mode.

Line Probe Data Format

*** %DF0 V.34 line probe data displayed in graph format.

%DF1 V.34 line probe data displayed in table format.

Line Probe Data Read

*** %DP0 Disable reading of line probe data during the V.34 handshake.

%DP1 Enable reading of line probe data during the V.34 handshake.

DTMF Detection

*** >DT0 Disable DTMF detection.

>DT1 Enable DTMF detection when off-hook.

Echo Command Mode Characters

*** E1

Do not echo command mode characters.

Do echo command mode characters.

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Appendix

&En

n = 0–15

V.42 Error Correction Modes

&E0 Non-error correction mode (V.42 disabled).

*** &E1 Auto-reliable mode.

&E2 Reliable mode (V.42 enabled).

Modem-Initiated Flow Control

&E3 Flow control disabled.

*** &E4 Hardware flow control.

&E5 XON/XOFF flow control.

XON/XOFF Pass-Through (&E5 selected)

*** &E6 XON/XOFF not passed through.

&E7 XON/XOFF passed through.

Hewlett-Packard ENQ/ACK Pacing

*** &E8 ENQ/ACK pacing off.

&E9 ENQ/ACK pacing on.

Non-Error Correction Mode Flow Control

*** &E10 Non-error correction mode flow control off.

&E11 Non-error correction mode flow control on.

Pacing (Computer-Initiated Flow Control)

&E12 Pacing off.

*** &E13 Pacing on.

Data Compression

&E14 Data compression disabled.

*** &E15 Data compression enabled.

$En

n = 0 or 1

n = 0–5

V.42 Error Correction at 300 bps

*** $E0

$E1

V.42 error correction at 300 bps disabled.

V.42 error correction at 300 bps enabled.

$EBn

%En

Asynchronous Word Length

*** $EB0 10-bit mode enabled.

$EB1 11-bit mode enabled.

Escape Sequence Options

%E0 Modem won’t escape.

*** %E1 +++ method.

%E2 Break method.

%E3 Either +++ or break methods.

*** %E4 No OK response to +++.

%E5 OK response to +++.

&Fn

n = 0, 8, or 9

Load Default Configuration

&F0 Load factory default values from ROM.

*** &F8 Read factory default values and DIP switch settings when &F is issued.

&F9 Read parameters stored in nonvolatile memory when &F is issued.

$Fn

n = 0 or 1

Auto-Reliable Fallback Character Enable

*** $F0

$F1

Do not fall back to non-error correction mode connect if CR received.

Fall back to non-error correction mode connect if CR received.

%Fn

Echo Canceler Offset Frequency Compensation

*** %F0 Disable echo canceler offset frequency compensation.

%F1 Enable echo canceler offset frequency compensation.

100

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Appendix

#Fn

n = 0, 1, or 2

Fallback Modes When Online

#F0

#F1

No fallback when online.

Fall back incrementally from maximum speed to 4800 bps.

*** #F2

Fall back incrementally to 4800 bps, fall forward when line improves.

&Gn

Guard Tones (International model only)

*** &G0 Turn off ITU-T guard tones.

&G1 Turn on ITU-T 550 Hz guard tone.

&G2 Turn on ITU-T 1800 Hz guard tone.

Note:The U.K. model is locked to &G2, which turns on the ITU-T 1800 Hz guard tone.

*Hn

n = 0 or 1

On-Hook/Off-Hook

Go on-hook (hang up).

Go off-hook.

Busy-Out After Disconnect

*** *H0

*H1

Disable busy-out after disconnect.

Enable busy-out after disconnect.

n = 0, 1, 2,

or 5

Inquire Product Codes

Request modem ID #.

Request firmware revision #.

Request modem description.

Request DSP version.

#Ix

x = password

Enter Login Password

Password is case sensitive.

#I=x

Store Login Password

Password must be 6–10 characters long, and may consist of any keyboard charac-

ters.

n = 0, 5–11

List Commands

List stored telephone numbers.

List current operating parameters.

List current S-register values.

List additional parameters.

List online diagnostic parameters.

List line probe signal strength data.

List line probe signal to noise ratio.

List line probe noise data.

L10

L11

Note: To use L9, L10, or L11 when online, you must first escape to command mode

by typing +++ATLn<CR> (for n type 9, 10, or 11). Type ATO to return on line.

#Ln

n = 0, 1, 2,

3, or 8

V.42 Error Correction Mode

*** #L0

Modems negotiate V.42 mode.

#L1

#L2

#L3

MNP on and LAP-M off (originate mode only).

LAP-M on and MNP off (originate mode only).

Disable detection phase and go directly to LAP-M.

n = 0, 1, 2,

or 3

Modem Speaker Control

*** M1

Modem speaker always off.

Modem speaker on until carrier signal detected.

Modem speaker always on.

Monitor speaker on during dialing, off during handshaking.

101

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Appendix

$MBn

n = speed

Modem Baud Rate

$MB75

Select ITU-T V.23 mode.

$MB300

$MB1200

$MB2400

$MB4800

$MB7200

$MB9600

Select 300 bps on line.

Select 1200 bps on line.

Select 2400 bps on line.

Select 4800 bps on line.

Select 7200 bps on line.

Select 9600 bps on line.

$MB12000 Select 12,000 bps on line.

$MB14400 Select 14,400 bps on line.

$MB16800 Select 16,800 bps on line.

$MB19200 Select 19,200 bps on line.

$MB28800 Select 28,800 bps on line.

*** $MB33600 Select 33,600 bps on line.

d = 0 or 1

Dial a Stored Number

Dial stored telephone number d.

NdNe...

d = 0 or 1

e = 1 or 0

Number Linking

Dial stored number d; if that is busy, dial stored number e. The command may be

extended NdNeNdNe... to cycle between the two numbers.

n/a

Go Back On Line

Exit command mode and go into online mode after using the escape code to do the

reverse.

In dialing

*** Pulse-Dial

command

Modem pulse-dials numbers that follow P.

&Pn

n = 0 or 1

Set Pulse Dial Ratios

*** &P0 60:40 pulse ratio.

&P1 67:33 pulse ratio.

Note:The ZDXK is locked to &P1, a 67:33 ratio.

n = 0–2

Result Codes Enable/Disable

*** Q0

Result codes sent.

Result codes suppressed (quiet).

No Response answer mode.

&Qn

n = 0 or 1

Result Codes (Multi-Tech or Standard AT)

*** &Q0 Multi-Tech responses with modifiers.

&Q1 Standard AT responses with no modifiers.

n = 0 or 1

Reverse Originate/Answer Mode

*** R0

Modem will not reverse modes.

Modem will reverse modes when R is added to dial string.

&Rn

n = 0, 1, or 2

Clear to Send Control

&R0 Let CTS state follow RTS state when online.

*** &R1 Force CTS high (on).

&R2 Let CTS drop on disconnect for time set by S24, then go high again.

&RAn

&RDn

n = 0 or 1

Asymmetric Bit Rate

*** &RA0 Enable asymmetric bit rate operation.

&RA1 Disable asymmetric bit rate operation.

Square Wave Ring Detect

&RD0 Full wave ring detect only.

*** &RD1 Full wave and square wave ring detect.

102

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Appendix

&RFn

n = 0 or 1

CTS/RTS Interaction Control

&RF0 Let CTS follow RTS.

*** &RF1 Let CTS act independently.

&RN

&RP

n/a

Rate Renegotiation

Forces the modem to renegotiate the data rate.

Immediate Line Probe

Initiates a retrain that makes the modem read line probe information if %DP1 is

selected. Valid only when online in V.34 mode.

&RR

$Rn

n/a

Retrain

Initiates an immediate retrain without a line probe reading.

n = 0 or 1

Retransmit Count

*** $R0 Disconnect after 12 retransmits.

$R1 Do not disconnect after 12 retransmits.

Sr=n

r = 0–11, 13,

24, 25, 30,

Set Register Value

Set value of S-register r to value of n, where n is entered in decimal format.

32, 34, 36,

37, 43, 48, or

94; n varies

Sr?

r = 0–11, 13,

24, 25, 30,

32, 34, 36,

37, 43, 48,

or 94

Read Register Value

Read value of S-register r and display value in 3-digit decimal form.

&Sn

n = 0, 1, or 2

Data Set Ready Control

&S0 Force DSR high (on).

*** &S1 Let DSR follow CD.

&S2 DSR drops on disconnect for time set by S24, then goes high again.

&SFn

$SBn

n = 0 or 1

DSR/CD Interaction Control

*** &SF0 Select DSR to follow CD.

&SF1 Select DSR to be independent.

n = speed

Baud Adjust

($BA) must

be off.

Serial Port Baud Rate

$SB300

Select 300 bps at serial port.

Select 1200 bps at serial port.

Select 2400 bps at serial port.

Select 4800 bps at serial port.

Select 9600 bps at serial port.

Select 12,000 bps at serial port.

Select 19,200 bps at serial port.

Select 38,400 bps at serial port.

Select 57,600 bps at serial port.

$SB1200

$SB2400

$SB4800

$SB9600

$SB12000

$SB19200

$SB38400

$SB57600

*** $SB115200 Select 115,200 bps at serial port.

#Sy

y = password

Enter Setup Password

Password is case sensitive.

#S=y

Store Setup Password

Password must be 6–10 characters long, and may consist of any keyboard charac-

ters.

In dialing

Tone-Dial

command

Modem tone-dials numbers following the T.

103

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Appendix

&Tn

$Tn

#Tn

n = 4 or 5

n = 0 or 1

n = 0–3

Respond to Remote Digital Loopback Signal

&T4 Enable response to remote digital loopback signal.

*** &T5 Disable response to remote digital loopback signal.

Calling Tone

$T0

*** $T1

Enable calling tone.

Disable calling tone.

Trellis-Coded Modulation

#T0

Disable trellis-coded modulation.

*** #T1

Enable trellis-coded modulation.

Loopback Test Modes

Enable analog loop originate mode.

Enable analog loop answer mode.

Enable remote digital loopback mode.

Enable local digital loopback mode.

n = 0 or 1

Result Codes (Verbose/Terse)

*** V1

Result codes sent as digits (terse response).

Result codes sent as words (verbose response).

#Vn

V.32terbo Handshake

*** #V0

#V1

Enable V.32terbo tones in answer mode.

Disable V.32terbo tones in answer mode.

In dialing

Wait for New Dial Tone

command

Causes modem to wait for new dial tone. (X2 or X4 must be selected.)

&Wn

n = 0 or 1

Store Configuration

&W0 Store current settings in NVRAM; modem will load these at power-on or with the

ATZ command instead of reading factory ROM defaults.

*** &W1 Do not store settings.

n = 0–4

Result Codes and Call Progress Selection

*** X0

Basic result codes (CONNECT only); does not look for dial tone or busy.

Extended result codes (w/ CONNECT 1200, CONNECT 2400, etc.); does not

look for dial tone or busy signal.

Extended result codes with NO DIAL TONE; does not look for busy signal.

Extended result codes with BUSY; does not look for dial tone.

Extended result codes with NO DIAL TONE and BUSY.

#Xn

n = 0 or 1

n/a

Number of XOFF Characters Sent

*** #X0

#X1

Single XOFF character sent after buffer is full.

Multiple XOFF characters sent (one for every character received after buffer is

full).

Long Space Disconnect

*** Y0 Disable sending or responding to long space break signal on disconnect.

Enable sending or responding to long space break signal on disconnect. (Both

modems must have Y1 set.)

Modem Reset

Reset modem to default values. Defaults come from NVRAM if &W0 is set, from ROM

if &W1 is set.

In dial

Dialing Pause

command

Comma; causes dialing pause for time set by S8.

104

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Appendix

At end of dial

command

Continuous Redial

Colon; causes continuous redial of number until answered (10 in North American

models). Not used in U.K. or International models.

;

At end of dial

command

Return to Command Mode After Dialing

Semi-colon; causes immediate return to command mode after dialing.

In dial

Flash On-Hook

command

Exclamation; causes modem to flash on-hook.

In dial

Quiet Answer

command

Causes modem to wait for a ringback, then 5 seconds of silence before processing

next part of command.

In dial

Call Card Tone Detect

command

Causes modem to wait for a call card tone before processing next part of command.

+++AT<CR>

Escape Sequence

Puts modem in command mode while still remaining on line. Type +++ followed by the

letters A and T, up to ten command characters (or as defined by S34), and a

RETURN.

%%%AT<CR>

Break Escape Sequence

Alternate escape method. Puts modem in command mode while still remaining on line.

Enter break signal followed by the letters A and T, up to sixty command characters,

and a RETURN.

Remote Configuration Escape Sequence

Cause remote modem to display remote configuration menu. Type %%% (or as

defined in register S13) followed by the letters A and T, and a RETURN.

105

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Appendix

Appendix F

RS-232C Interface Specifications

The MT2834MR6’s serial interface circuits have been designed to meet the electrical specifications in EIA

(Electronic Industries Association) Recommended Standard 232, Revision C (RS-232C). All signals

generated by the modem are approximately 10 volts when measured across a load of 3000 ohms or greater.

The receiving circuits of the modem accepts signals in the 3 to 25 volt range. The voltage thresholds are

defined as follows:

Negative: voltage more negative than 3 volts with respect to signal ground

Positive: voltage more positive than +3 volts with respect to signal ground

SignalInformation

Negative

Positive

Binary State

Signal Condition

Control and Timing Function

One

Mark

Off

Zero

Space

The input impedances of all modem circuits that accept signals from the data processing terminal or CPU

equipment are 4.7KW. For more specific details, consult the EIA RS-232C standard. The following chart lists

the EIA RS-232C interface pins and circuits present on the MT2834MR6’s RS-232C serial interface

connector. All other pins are unused.

Multi-Tech

EIA

Signal

Assignment Designation

Circuit

Source*

Circuit Function

RTS

CTS

DSR

XTC

OOS

—

Protective Ground

Transmitted Data

Received Data

Request to Send

Clear to Send

Data Set Ready

Signal Ground

Data Carrier Detector

Test Voltage

High Speed

Transmit Clock

Receive Clock

Data Terminal Ready

Ring Indicator

External Transmit Clock

Terminal Busy

DTE

DCE

DTE

DCE

—

DCE

DTE

DCE

DTE

* DTE = Data Terminal Equipment (terminal or computer)

DCE = Data Communications Equipment (the modem)

The computer or terminal should be supplied with a cable terminated with a Cinch DB25P or equivalent

connector mounted in a Cinch DB51226-1 or equivalent hood assembly as specified by the EIA RS-232C

standard.

106

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Appendix

Functional Description of the RS-232C Signals

Transmitted Data (TD) — Pin 2 (To modem)

Signals on this circuit are generated by the local computer and passed to the modem’s

transmitter. A positive signal is a space (binary 0) and a negative signal is a mark (binary 1).

The transmitting computer should hold this line in the marking state when no data is being

transmitted, including intervals between characters or words. The TD LED indicates the

status of this circuit.

Received Data (RD) — Pin 3

(From modem)

The circuit is the data output of the modem. Data signals received from the remote modem

are passed to the local computer on this line. When no carrier signal is being received (pin

8 negative), this line is forced into a marking condition. The RD LED indicates the status of

this signal.

Request To Send (RTS) — Pin 4 (To modem)

This signal, from the computer, indicates to the modem that the computer has data to

transmit.

Clear To Send (CTS) — Pin 5

(From modem)

This signal indicates to the computer that the modem is ready to transmit any data present

on the Transmit Data line (pin 2).

Data Set Ready (DSR) — Pin 6 (From modem)

This signal indicates indicates that the modem is in data mode and is connected to the

communications channel. This signal is on during analog-loop-test mode.

Signal Ground (SG) — Pin 7

The SG pin is connected to the modem’s signal ground. It establishes the common ground

reference for all the other interface signals.

Carrier Detect (CD) — Pin 8

(From modem)

A high CD signal (positive voltage) indicates that a carrier signal has been received from

the other modem. This circuit does not typically turn on in the presence of message circuit

noise or out-of-band signals. There is a one-second delay between when the carrier tone is

detected and when the CD circuit is turned on.

This signal goes off if received data carrier falls below the receiver threshold for more than

37 ms. When CD is off, the Received Data circuit (pin 3) is held to the marking state.

107

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Appendix

Test Voltage (+V) — Pin 9

(From modem)

This test pin has 330 ohms of resistance to +12 volts DC. It can be used to strap other

signals high. For example, if the terminal does not supply a DTR (Data Terminal Ready)

signal, pin 9 can be jumpered to pin 20 (DTR) on the RS-232C connector or cable to force

DTR on.

High Speed (HS) — Pin 12

(From modem)

The high state of this circuit indicates that the modem is in the high speed (1200 bps) mode.

This circuit is commonly used to signal the computer or terminal to which the modem is

connected to switch to its 1200 bps setting.

Transmit Clock (TC) — Pin 15

(From modem)

The TC signal does not apply to the MT2834MR6, since it is used only in the synchronous

mode. The clock is a square wave and is used to provide the computer or terminal with

timing information for its Transmit Data circuit (pin 2). This clock is provided on the interface

at all times when the modem is in synchronous mode.

The first signal element of the Transmitted Data signal should be presented by the terminal

on the first positive (off to on) transition of TC after the CTS circuit on pin 5 is turned on. The

transmitted data is sampled by the modem on negative transitions of TC.

Receive Clock (RC) — Pin 17

(From modem)

The RC signal has the same characteristics as the TC signal, with the exception that it is

used to provide the computer or terminal with timing information for its Receive Data (pin 3)

circuit. The RC signal’s negative transition (on to off) indicates the center of each signal

element on the Received Data circuit.

Data Terminal Ready (DTR) — Pin 20 (To modem)

The DTR signal provides a means for the computer to control the modem’s connection to

the communications channel. A high DTR signal is required by the modem to be able to

communicate. Turning DTR off for more than 50 ms forces the modem to disconnect.

The most common use of DTR is in autoanswer applications. A frequently used method is to

have the computer turn on DTR in response to RI (Ring Indicator), which allows the modem

to answer. Later, DTR is turned off at the conclusion of the log off procedure, which forces

the modem to disconnect, enabling it to receive another call. In non-autoanswer

applications it is advisable to leave DTR on. This is the standard factory setting. An

alternative is to provide a constant high DTR from the terminal or computer.

108

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Appendix

Ring Indicator (RI) — Pin 22

(From modem)

This signal remains on for the duration of the ringing signal. When a ring signal is received

by the modem, the modem automatically answers after the first ring. The modem can

answer after a specified number of rings which can be programmed in command mode, but

if none is specified, the modem answers after the first ring.

External Transmit Clock (XTC) — Pin 24

(To modem)

Supplies the same function as the Transmit Clock signal on pin 15.

Terminal Busy (OOS) — Pin 25 (To modem)

The Terminal Busy/Out of Service (OOS) circuit is not defined in the RS-232C standard, but

is used by Multi-Tech Systems and most manufacturers to make the phone lines busy to

incoming phone calls. Pin 25 is not typically connected to the RS-232C interface when

shipped from the factory; it can be ordered connected as an option. If pin 25 is connected

and is brought high, the modem is placed off hook, and is busy to incoming calls.

109

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Appendix

Appendix G

Cable and Connector Diagrams

RS-232C Serial Cable

Frame Ground

Transmit Data

Receive Data

Request to Send

Clear to Send

Data Set Ready

Signal Ground

Carrier Detect

+ Voltage Test

High Speed

Transmit Clock

Receive Clock

Data Terminal Ready

Ring Indicator

Terminal Busy

25-pin male connector (DB-25P)

25-pin female connector (DB-25S) on back of rack

Connects to terminal or computer RS-232C interface (serial port). Gender and pin-out depends on device.

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Appendix

APPENDIX H

Introduction to MultiTech Escape Methods

You may sometimes find it necessary to issue AT commands to your modem, while you are online with a

remote modem, without disconnecting the call. If so, you will want to take advantage of escape methods that

allow you to change the modem’s mode of operation from online mode to command mode. After you issue

your AT commands, you may return to online mode, but typically most users escape so that they can hang up

a modem upon completion of a call.

Our modems offer two escape methods: in-band and out-of-band. Both incorporate Time Independent

Escape Sequence (TIES) methodology. An escape sequence is a pattern or sequence that the modem

recognizes as its signal to shift from online mode to command mode. “Time independent” means that the

modem recognizes the escape sequence without a prefixed and/or suffixed delay.

In an in-band escape, the modem recognizes the escape sequence as a pattern sent to it as part of the data

stream or band (hence its name).

In an out-of-band escape, the escape sequence is a pattern that cannot and does not occur in the data

stream.

Our in-band escape method is +++AT<CR>

Our out-of-band escape method is <BREAK>AT<CR>

A break signal cannot be sent as part of a data file; instead it is sent by a direct program command to the

UART used by the computer.

The break signal is defined as either the transmission of binary 0 for a minimum of 10 bits; or as a minimum

interval of 135 milliseconds as established in the ITU-T X.28 standard. Routines in high level languages, and

keys on most computers, can send the break signal for fixed intervals.

111

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Appendix

How to Select an Escape Method

If you want your modem to escape and then wait for you to issue a command before it will return to online

mode, then use +++AT<CR>. For example, use this method if you find you need to review a help screen in

the middle of a communications session.

If you wish to combine the escape with a command (or commands) and with an immediate return to online

mode, then use the <BREAK>AT<CR> method. You may also use this method to have the modem wait

before it will return on line.

The following AT commands are used to select the modem’s escape method:

%E0 Escape disabled

%E1 +++AT method

%E2 BREAK AT method

%E3 Both methods enabled

%E4 Disable OK to +++ escape

%E5 Enable OK to +++ escape

Escape Method 1: +++AT<CR>

In the following example, a user who is in online mode decides to set S0 to 1 to configure

the modem to answer on the first ring.

1. The user types the sequence +++AT<CR>. The sequence is sent to the modem

2. The modem transmits the +++.

3. The modem buffers AT and starts the wait-for-<CR> timer.

4. Upon receiving the <CR> the modem escapes to command mode.

5. The modem responds OK.

6. The user enters the command ATS0=1<CR>. This sequence is sent to the modem.

7. The modem buffers ATS0=1<CR> and identifies it as a valid command.

8. The modem executes the command, setting the contents of S0 to 001.

9. The user sends ATO<CR> to the modem.

10. The modem returns to online mode.

Escape Method 2: <BREAK>AT<CR>

In the following example, a user who is in online mode decides to set S0 to 1, to configure

the modem to answer on the first ring.

1. The break signal is sent to the modem.

2. The modem buffers the break signal.

3. The modem starts the S32 wait-for-<CR> timer.

4. ATS0=1<CR> is sent to the modem.

5. The modem buffers ATS0=1<CR> and identifies it as a valid command.

6. The modem escapes to command mode.

7. The modem executes the command, setting the contents of S0 to 001.

8. The modem returns to online mode.

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Appendix

S-Registers and Escape Sequence

There are two S-registers to modify the functioning of escape sequences. Register S32 establishes a value

for how much time may elapse between the receipt of the beginning of the escape sequence, whether

<BREAK> AT or +++AT, and the receipt of a <CR>. This interval is known as wait-for-<CR>-time, or break

passthrough.

Assign a value in increments of 100 milliseconds to S32. The default value is 20, or 2 seconds. In the

+++AT<CR> method, the wait-for-<CR>-time interval begins once the A in +++AT is received by the modem.

In the <BREAK> AT method, the wait-for-<CR>-time interval begins once the modem has received the break

signal.

number of characters the modem can buffer following an AT, before a <CR> must be received. The default

value is 10 characters. Do not confuse this buffer size with the regular command mode buffer length of 60

characters.

Aborting an Escape Sequence

The +++AT<CR> escape will abort if you do not issue a <CR> before the wait-for-<CR>-time interval expires.

The <BREAK>AT<CR> method will also abort if you do not issue a <CR> before the wait-for-<CR>-time

interval expires, and also if any of the following occurs:

1. An illegal sequence is detected, including:

a) A character other than A follows <BREAK>;

b) A character other than T follows <BREAK>A;

c) Two <BREAK>s are received in succession.

2. The command buffer overflows before a <CR> occurs.

If you have any questions regarding the information in this appendix, please contact Technical Support (see

Chapter 7).

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Appendix

APPENDIX I

Introduction to Remote Configuration

Remote configuration, a feature of Multi-Tech’s MT2834MR6 modems, is a network management tool that

allows you to configure modems anywhere in your network from one location. With password-protected

remote configuration, you can issue AT commands to a remote Multi-Tech modem for maintenance or

troubleshooting as if you were on site.

Basic Procedure

The following steps are valid regardless of whether the connection is established by the local or the remote

Multi-Tech modem.

1. Establish a data connection with a remote modem that has the remote configuration feature.

2. Send three remote configuration escape characters followed by AT and an ENTER. Example:

%%%AT<CR>. The remote modem responds with the following menu:

1. DATA Mode

2. COMMAND Mode

3. Enter the number 2. The remote modem responds with a request for the setup password:

Password>

4. Enter your setup password. If the password is correct, the remote modem responds with:

5. You can now send AT commands to the remote modem.

6. When you have finished configuring the remote modem, save the new configuration by typing

AT&W0<CR>, then type ATO<CR> to exit remote configuration. The modem responds with the following

menu:

1. DATA Mode

2. COMMAND Mode

7. Type the number 1 to return to data mode. You can then break the connection in the normal way.

CAUTION: If you hang up while you are in remote configuration mode, it may lock up the remote modem.

Setup

The first time you configure a modem remotely, you should set its passwords and possibly its remote

configuration escape character. Multi-Tech modems are shipped with a default login password (MULTI-

TECH) and setup password (MODEMSETUP). Because anyone who has an owner’s manual knows the

default passwords, for security you should change them—but don’t forget them!

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Appendix

Changing the Passwords

1. Establish a remote configuration link with the remote modem as described above.

2. Type AT#IMULTI-TECH (or AT#Ixxxxxx if you have replaced the MULTI-TECH password with xxxxxx)

and press ENTER. The modem responds with OK if the login password is correct, and ERROR if it is

wrong.

3. Type AT#SMODEMSETUP (or AT#Syyyyyy if you have replaced the MODEMSETUP password with

yyyyyy) and press ENTER. The modem responds with OK if the setup password is correct, and ERROR

if it is wrong.

4. To change the login password, type AT#I=xxxxxx, where xxxxxx stands for the password, and press

ENTER. The password may include any keyboard characters, but must be six to ten characters long. The

modem responds with OK.

5. To change the setup password, type AT#S=yyyyyy, where yyyyyy stands for the password, and press

ENTER. The password may include any keyboard characters, but must be six to ten characters long.

The modem responds with OK.

6. The new passwords are saved automatically. You may now either enter more AT commands or exit

remote configuration with ATO<CR>. The next time you remotely configure the modem you must use the

new setup password.

Note: Passwords are case sensitive. The next time you enter the password, it must be in the same case as

you set it up.

Changing the Remote Escape Character

To increase security, you may wish to change the remote modem’s remote configuration escape character.

The remote configuration escape character is stored in register S13. The factory default is 37, which is the

ASCII code for the percent character (%). Setting S13 to 0 (zero) will disable remote configuration entirely—

but if you do this remotely, you won’t be able to change it back remotely!

1. Establish a remote configuration link with the remote modem as described above.

2. Type ATS13=n, where n is the ASCII code for the new remote configuration escape character, then press

ENTER.

3. Save the new value by typing AT&W and pressing ENTER.

4. Type ATO<CR>, then 1, to exit remote configuration.

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Index

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Index

&BS 49, 78

&C 41, 60

&CD 37

Index

&D 41

&E0 43

&E1 43

&E10 50

&E11 50

&E12 51

&E13 51

&E14 43

&E15 43

&E2 43

&E3 49

&E4 49

&E5 50

&E6 50

&E7 50, 73

&E8 50

&E9 50

&F 32, 64

&G 38

&P 38, 92

&Q 34

&R 41, 60

&RA 40

&RD 38

&RF 42

&RN 48

Aborttimer 19, 21, 28, 29, 59, 63

Analog loopback test 82

Answercommand 21, 52

Answermode 27, 46, 52

AnswerTonecommand 36

Answerbackcommand 35

Answering a call 52, 63

Asymmetric Bit Rate command 40

AsynchronousWordLengthcommand 49

ATCommandControlcommand 21, 36

ATCommandSummary 98

AT commands 21

, (comma) 28, 59

! (exclamation mark) 28

#A 36

#F 37

#I 53

#L 43

#S 53

#T 39

#V 40

#X 51

&RP 54

&RR 48

&S 42, 60

&SF 42

$A 44, 78

$BA 45, 46, 76, 77

$E 44, 79

$EB 49

&T 55, 83

&W 32, 33, 63, 64

*H 38, 62

+++AT<CR> 19, 52, 111, 112, 113

$F 44, 78

$MB 36, 45, 76

$R 44, 79

$SB 46, 77

$T 39

%%%AT<CR> 53

%DC 21, 36

%DF 54

%DP 54

%E 52

%F 40

&A 35

: (colon) 28

; (semicolon) 28

<BREAK>AT<CR> 52, 111, 112, 113

>DT 37

21, 52

A/ 47

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Index

A: 26

AT 21, 22

attention code 21, 22

Backspacecharacter 22, 58

Baud Adjust command 45, 76, 77

Baudrate

command string limit 22

21, 26

modem 45

serial port 45, 46

Bellstandards 36

D...N... 30

disabling command mode 21, 36

Blinddialing 26, 30, 35

Breaksignal 39, 60, 113

definition 111

editing 22

functional summary 23, 24, 25

escape sequence 52

19, 26

Busy Out After Disconnect command 38

Busy signal 26, 28, 30, 35, 38, 59

Busy switches 15

Busy-Out After Disconnect command 62

Busy-out state 15

L10 54

L11 54

L5 47, 64

L6 47, 64

L7 47, 64

L8 47, 55

L9 54

Call Card Tone Detect command 29

Calltermination 19

N 30

N...N... 30

CallingTonecommand 39

CanadianLimitationsNotice 11

Carriagereturncharacter 58

CarrierDetectControlcommand 41

Carrier, loss of 59

parameters 22

CBX phone systems 41, 60

CDsignal 15

R 27

S = 63

control of 41

S ? 63

structure of 22

summary 98

disconnect drop time 60

DSR interaction 42

LED indicator 82

U 55

W 27

response time 59

Clear to Send Control command 41

CleardownatDisconnectcommand 37

Comma 59

27, 28, 35

Commandbuffer 22, 61, 113

Commandmode 21, 111

disabling 21, 36

Autoanswer 18, 21, 45, 57, 63

disabling 57

AutoreliableBufferingcommand 44, 78

AutoreliableFallbackCharactercommand 44

Autoreliablemode 43, 44

Commandmodecontrol 36

Commandstring 21, 30

Compression,data 66, 68, 74

Configuration

default 33

AutoreliableModecommand 43, 70

ContinuousRedialcommand 26, 28

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Index

CTS signal

control of 41

disconnect drop time 60

flow control 49

DTE(dataterminalequipment) 51

DTMF(dualtonemultifrequency)

detection 37

dialing 27

RTS interaction 42

CTS/RTSinteractioncontrol 42

frequencies 93

DTMFDetectioncommand 37

DTRsignal 18, 19

busy-in time 61

busy-out time 61

control of 41

disconnect drop time 60

DAA

Data bit 49

Datacompression 66, 68, 74

speed conversion 45

DataCompressioncommand 43

Data Set Ready Control command 42

DataTerminalReadyControlcommand 41

EchoCancelerFrequencyOffsetCompensation

comman 40

DescriptionofMT2834MR6

Diagnosticcommands 55

Dial a Stored Number command 30

Dialcommand 21, 26

Dial pulses 92

EchoCommandModeCharacterscommand 34

ENQ/ACK Pacing command 50

Errorcorrection 66, 68, 74

at 300 bps 44

automatic 43

Dialtone 26

disabling 43

wait time 35, 58

selecting 43, 44

Dialtonefrequencies 93

Dialing

a phone number 26

a stored number 30

automatic 12

blind dialing 26, 30, 35

continuous redialing 26

modifiers 27

ErrorCorrectionModescommand 43

Escape code character 57

Escape Sequence Options command 52

Escapesequencetimeout 61, 113

Escapesequences 52, 112

+++AT<CR> 52, 111, 112

<BREAK>AT<CR> 52, 111, 112

aborting 113

pause time 28, 59, 63

smart dialing 26, 35

DialingPausecommand 28

Digital loopback tests 83, 84

DimensionsofMT2834MR6 14

Disconnect delay time 19

Disconnecting 44

in-band 111

Multi-Tech 111

options 52

out-of-band 111, 113

remote configuration 53

S-registers 112, 113

selecting 112

after DTR drop 60

Extendedcodes 35

drop time 41, 42, 60

inactivity timer 61

Display Line Probe Data command 54

DSRsignal

CD interaction 42

control of 42

disconnect drop time 60

Fallback 36, 37

Fallback Modes command 37

Faxwarning 10

FCCregulations 9, 10

File transfer protocol 68

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Index

FlashOn-Hookcommand 28

Flowcontrol 41, 49, 50, 51, 74

commands 49

LoadDefaultConfigurationcommand 32

LoginPasswordcommand 53

Longspacebreak 39

CTS/RTS enable 49

disabling 49

Long Space Disconnect command 39

Loopback Test Modes command 55

LoopbackTesting 81

hardware (RTS/CTS) 72

no-error correction mode 73

non-error correction mode 50

software (XON/XOFF) 72

XON/XOFF pass through 50

FlowControlDisablecommand 49

Format Line Probe Data command 54

Fuses 14

Loss of carrier 19

Manualorganization

Maximum Block Size command 78

Maximum Reliable Block Size command 49

Memory

nonvolatile (NVRAM) 22, 30, 32, 33, 64

read-only (ROM) 22, 32, 33, 64

MNP3–5 49, 68

MNPerrorcorrectionenable 43

ModemBaudRatecommand 36, 45, 76

Modesofoperation 70

Go Back Online command 52

GuardTonescommand 38

Multi-Tech Internet sites 89

MultiModemManagerSoftware 81

Handshake 18, 36

Hangingup 19, 26, 111

HardwareFlowControlcommand 49

Noise 39, 61

Non-errorcorrectionmode 44, 50, 61, 70

Non-ErrorCorrectionModeFlowControlcom-

mand 50

NumberLinkingcommand 30

Number of XOFF Characters command 51

NVRAM (nonvolatile random access

memory) 22, 30, 32, 33, 64

ImmediateLineProbecommand 54

Inactivity timer 19, 61

Indicators 15

IndustryCanadaregulations 26

InquireProductCodecommand 47

Installation 16

Internetaddresses 89

Kermit 67

On-Hook/Off-Hookcommand 26

Onlinemode 21, 52, 57, 82, 83, 111

orderingreplacementparts 89

Originatemode 27, 46, 82

LEDindicators 15

Linefeedcharacter 58

Lineprobe 54

Originating a call 43, 45

Out-of-bandescapesequence 52

Out-of-service state (OOS) 15

Out-of-servicetime 38, 62

ListCurrentOperatingParameterscommand 47

List Current S-Register Values command 47

List Online Diagnostics command 47

ListStoredTelephoneNumberscommand 31

Listing stored values 31, 47

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Index

ResultCodesEnable/Disablecommand 34

Retraincommand 48

Pacing 49, 50, 73

enable/disable 51

ENQ/ACK 50, 73

Pacingcommand 51, 74

Parameters 22, 32, 47

default 22, 41

RetransmitCountcommand 44, 79

Returncharacter 58

ReturntoCommandModecommand 28

ReverseOriginate/AnswerModecommand 27

Rings

counting 57

Parity 49

number till answer 57, 63

square wave detection 38

ROM(read-onlymemory) 22, 32, 33, 64

RS-232C 41, 42, 49

PBX phone systems 27, 60

PBX/CBX disconnect drop time 41, 42, 60

Power 14

Pulse ratios, setting 92

Pulse-Dialcommand 27

Pulse-DialRatioscommand 38

cable and connector diagrams 110

controls 41, 42

specifications 106

RTS signal 41

QuietAnswercommand 28

CTS interaction 42

S-registers 47, 63, 113

assigning a value 63

definition 57

reading 63

S0 57, 63

S1 57

RateRenegotiationcommand 48

RDsignal 15

ReadLineProbeDatacommand 54

Reliablemode 43, 49

ReliableModecommand 43, 70

Remoteconfigurationescapecharacter 60

RemoteDigitalLoopbackcommand 55

RepeatLastCommandcommand 47

replacementparts 89

S10 19, 59

S11 60

S13 60

S17 60

ResetModemcommand 33

Responsecommands 34

Resultcodes 22, 34, 35, 75

call progress selection 35

enable/disable 34

extended codes 35

Multi-Tech 94

set selection 34

S2 57

S24 41, 42, 60

S25 60

S3 58

S30 19, 61

S32 61, 112, 113

S34 61, 113

S36 61

standard 95

S37 61

summary 94

S4 58

verbose/terse selection 35

Result Codes (Multi-Tech or Standard AT)

command 34

ResultCodes(Verbose/Terse)command 35

Result Codes and Call Progress Selection

command 27, 35

S43 62

S48 62

S5 22, 58

S6 26, 35, 58

S7 19, 21, 28, 29, 59, 63

S8 28, 59, 63

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Index

S9 59

S94 38, 62

asymmetric bit rate 40

connect speed 62

summary 96

Safety 16

echo canceler frequency offset compensa-

tion 40

Serial port baud rate 46

Serial Port Baud Rate command 77

Set Pulse Dial Ratios command 92

SetupPasswordcommand 53

Smartdialing 26, 28, 35

Specifications 12

Speedconversion 45, 46, 66, 75

Speed, data transmission 15

Speedindicator 15

V.32terbo handshake 40

V.42 43, 44

V.42 Error Correction at 300 bps command 44

V.42ErrorCorrectionModecommand 43, 69

V.54 tests 82, 83, 84

Wait for New Dial Tone command 27

Wait-for-carriermode 21

Square Wave Ring Detect command 38

Start bit 49

Stop bit 49

X.28 111

Xmodem 67

XON/XOFF 50, 51

XON/XOFFFlowControlcommand 50

XON/XOFFPass-Throughcommand 50

StoreConfigurationcommand 32, 33, 64

StorePhoneNumbercommand 30

Storingaconfiguration 32, 63

TD signal 15

Technical specifications 12

Terminalmode 83

Terminating a call 19

Testing 55, 81, 83, 84

commands 55

loopback tests 55, 81, 82, 83, 84

Timeindependentescapesequence 111

Tonedetection 37

Tonedialing 93

Tone-Dialcommand 27

Tone-dialing 60

Transmissionspeed 45, 46

Trellis-CodedModulationcommand 39

V.21 36

V.22 36

V.22bis 36

V.32 37

V.32bis 37

V.32terbo 37, 40

V.32terboHandshakecommand 40

V.34 37, 40, 54

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S000326A

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