PowerLogix Computer Accessories COM128 User Manual

PowerLogic^®COM128

RS-232 to RS-485 Converter

Installation and Operation Guide

August 2006

Download from Www.Somanuals.com. All Manuals Search And Download.

Conventions

Throughout this operation manual, the following methods are used to highlight

important information.

NOTE

Describes important considerations related to a device setup, feature or

application.

CAUTION

Alerts you to a condition which could potentially cause damage to the device or

other external equipment.

WARNING or DANGER

Warns you to avoid conditions that could potentially cause serious personal injury

and/or equipment damage.

Download from Www.Somanuals.com. All Manuals Search And Download.

Table of Contents

COM128FEATURES ................................................................................................. 1

INTRODUCTION ........................................................................................................ 2

PhysicalFeatures ..................................................................................................... 3

RS-232Panel ............................................................................................................. 3

RS-485Panel ............................................................................................................. 3

CONFIGURATION...................................................................................................... 4

ConfigurationSwitches ............................................................................................... 4

ModeDescriptions...................................................................................................... 4

2.1

2.2

3.1

3.2

3.2.1

3.2.2

3.2.3

3.2.4

3.2.5

RS-485FlowControl................................................................................... 4

SpeedCompensation ................................................................................. 5

RTS / CTS Flow Control ............................................................................. 5

RS-485DataBuffering ................................................................................ 6

Repeater ..................................................................................................... 6

4.1

4.2

INSTALLATION ......................................................................................................... 7

DCSupplyConnections.............................................................................................. 7

RS-232Connection&Configuration ........................................................................... 7

4.2.1

4.2.2

4.2.3

RS-232Cable ............................................................................................. 7

Direct Connection to a Computer................................................................ 7

Connection to a Modem.............................................................................. 8

4.3

RS-485BusConnections ........................................................................................... 9

4.3.1

4.3.2

4.3.3

ConvertorConnections ............................................................................... 9

GeneralBusWiringConsiderations ............................................................ 9

RecommendedTopologies ......................................................................... 9

SUPPLYING POWER TO THE RS-232 DTR PIN .................................................... 11

TECHNICALSPECIFICATIONS .............................................................................. 13

COM128OPTIONS .................................................................................................. 14

-UNIOption .............................................................................................................. 14

-INDOption .............................................................................................................. 14

7.1

7.2

Download from Www.Somanuals.com. All Manuals Search And Download.

COM128 InstallationandOperationManual

SchneiderElectric

COM128

MULTI-PORT RS-232 TO RS-485 CONVERTER

FEATURES

•

Connects one RS-232 line to four RS-485 buses.

•

Compatible with short-haul modems and line

drivers that are powered by the RS-232 line.

•

Automatic baud rate detection supporting data

rates of 1200, 2400, 4800, 9600, and 19200 baud.

Works directly with M-SCADA, L-SCADA

and PowerView software, or with other

proprietary software.

•

DTE or DCE operation allows connection to

computers or modems without the need for null

modem adapters.

•

Full electrical isolation between RS-232 and RS-

485 to 750 VDC

•

RS-485 transmit enable may be controlled

automatically, or by the RS-232 RTS line.

Microprocessor control allows for future

enhancements by firmware upgrade.

RTS/CTS handshaking capability for use with radio

modems.

Download from Www.Somanuals.com. All Manuals Search And Download.

COM128 InstallationandOperationManual

SchneiderElectric

DTEORDCEOPERATION

INTRODUCTION

The COM128 is switch-selectable to act in DTE or

DCE mode. An RS-232 port is provided for each mode,

eliminating the need for null-modems.

The COM128 is used to interface a single RS-232 communica-

tions line to up to four RS-485 communications buses.

The RS-485 standard restricts each RS-485 bus to supporting

32 or fewer devices connected to it. The standard also dictates

a 4000 foot (1219 m) maximum overall cable length on an RS-

485 bus. The COM128 is ideal for installations that contain

more than 32 remote devices, or that have devices positioned at

distances greater than could be reached with a 4000 foot cable.

In DTE mode, the COM128 supports a CTS-WAIT mode in

which received RS-485 packets will be buffered until the CTS

line indicates the RS-232 device is ready to receive the data.

This feature is useful when interfacing radio modems or slow

data logging equipment to RS-485 devices.

The COM128 has four physically independent RS-485 ports,

allowing communications with up to 128 devices. Data is

transmitted to all four RS-485 ports simultaneously (ie. the

ports are not addressable).

AUTOMATICBAUDRATEDETECTION

The microprocessor within the COM128 continuously monitors

the data being received on its RS-232 port, and determines the

correct baud rate. No jumper or switch settings are required.

The COM128 provides many features which make it flexible,

easy to use, and reliable:

HIGHELECTRICALISOLATION

TWOMETHODSOFRS-485BUSCONTROL

RS-485 buses are generally quite long, and are often run

through electrically noisy environments. The risk of exposure to

transient voltage surges and spikes on an RS-485 line is

substantially higher than on an RS-232 line. The COM128 uses

optical isolation between RS-485 and RS-232 sections to

provide 750 VDC electrical isolation, and includes transient

suppression circuitry on its RS-485 ports.

RS-232 is a duplex communications standard, allowing signals

to be transmitted and received simultaneously. RS-485 is half

duplex standard, allowing only one device connected to an RS-

485 bus to transmit at any given time.

The COM128 has two ways to determine whether it should be

transmitting onto the RS-485 buses, or listening to them:

1) The COM128 can use the RTS signal generated by a

computer or other device connected to the RS-232 port.

When the RTS line is asserted, the COM128 will convert

the RS-232 data stream to RS-485 signal levels and

transmit onto the RS-485 buses. When the RTS signal is

de-asserted, the COM128 will listen for data on the RS-

485 bus and pass it through to the RS-232 port.

MICROPROCESSORCONTROL

Unlike most converters, the COM128 is controlled by a

microprocessor. COM128 features are determined by the

processor, not by its electrical circuitry. As new features

become available, they can be added to the COM128 by a

simple firmware upgrade. This process requires the replace-

ment of a single chip, allowing upgrades to be performed in the

field in a matter of minutes.

2) Some types of modems and computer hardware/software

do not support RTS line operation. For these applications,

the COM128 has an Auto RTS mode which monitors the

RS-232 bus for data signals. When data is present, the

COM128 automatically enables the RS-485 transmit mode

and begins to transmit onto the RS-485 buses.

LINEDRIVERCOMPATIBILITY

Short-haul modem/line drivers, such as the Gandalf mLDS,

draw their power from the RS-232 DTR line. The COM128 will

support these devices by means of a simple process that

requires the movement of a jumper within the COM128 case.

The process requires only a screwdriver and should take no

more than a few minutes to perform. Please refer to Chapter 5

(Page 12) "Supplying Power to the RS-232 DTR Pin" for details.

Download from Www.Somanuals.com. All Manuals Search And Download.

COM128 InstallationandOperationManual

SchneiderElectric

2.2

RS-485PANEL

PHYSICAL FEATURES

The RS-485 panel of the COM128 is illustrated in Figure 2.2.1.

2.1

RS-232PANEL

RS-485 PORTS

These four ports connect the COM128 to the four

RS-485 buses. Four pluggable 3-pin terminal blocks are

provided.

The RS-232 panel of the COM128 is illustrated in Figure 2.1.1.

DC SUPPLY CONNECTORS

These connections allow the COM128 to be powered from a

wide range of DC voltage sources, including the supplied

adapter. See Chapter 4 for additional information.

STATUS INDICATORS

A. IN (RS-232)

This LED will flash to indicate that data is being passed

from the connected RS-232 port to the RS-485 ports.

RS-232 PORTS

These ports provide connection to either a computer (DCE) or

a modem (DTE) See Chapter 3 for configuration. See

Chapter 4 for connections.

B. IN (RS-485)

This LED will flash to indicate that data is being passed

from one of the four RS-485 ports to the connected RS-

232 port.

SWITCH

The 6-position switch is used to configure the operation of the

COM128. See Chapter 3 for additional details.

C. RS-485 OUT (A, B, C, D)

For each corresponding RS-485 port these LED’s indicate

if the port is in receive or transmit mode. If the LED is

on, the corresponding port is listening for data from the

RS-485 bus. If the LED is off, the corresponding port is

transmitting data to the RS-485 bus.

Figure 2.1.1

RS-232 Connection Panel

Figure 2.2.1

RS-485 Connection Panel

Download from Www.Somanuals.com. All Manuals Search And Download.

COM128 InstallationandOperationManual

SchneiderElectric

Figure 3.1.1

COM128 Configuration Switches

CONFIGURATION

3.1

CONFIGURATIONSWITCHES

SWITCHES

These six switches are used to configure the COM128 for the

desired operation (see Figure 3.1.1). A switch is ON when it is

in the UP position. The following is a description of each mode

of operation. A list of switch settings for the different modes

follows each mode description. The configuration switches are

only read when control power is initally applied to the

COM128. To re-configure the COM128, the control power

must be removed and re-applied.

OFF

3.2

MODEDESCRIPTIONS

RS-485FLOWCONTROL

NOTE

3.2.1

Setting the Configuration Switches to an

undefined value will cause the COM128 to

continually reset.

FUNCTION

This mode is used to convert the RS-232 signals from either a

DTE or DCE device to RS-485 signals. The COM128 makes the

signal conversion and provides the timing control signals for

the RS-485 ports. No data buffering takes place. Timing can be

set for a fixed baud rate or the COM128 is able to do auto-

matic baud rate detection on the incoming RS-232 data. Either

the DTE or DCE port can be programmed. When the DTE port

of the COM128 is selected in automatic baud rate detection

mode, the input CD (Carrier Detect) signal from the DCE

device can be used to control the transmission of RS-232 data

from the COM128 to the DCE device.

For applications where a DTE device uses the RS-232 RTS

signal for flow control the COM128 can be programmed to use

the RTS signal to control the RS-485 ports.

Mode

Port

Baud

SW1 SW2 SW3 SW4 SW5 SW6

RS-485 Flow Control @ fixed Baud Rate

DTE

1200

2400

4800

9600

19,200

OFF

RS-485 Flow Control @ fixed Baud Rate

DCE

1200

2400

4800

9600

19,200

OFF

RS-485 Flow Control with Auto Baud Rate Detect

DCE

DTE

DCE

OFF

RS-485 Flow Control with Auto Baud Rate Detect

RS-485 Flow Control with Auto Baud Rate Detect and Carrier Detect Required

RS-485 Flow Control with Hardware RTS

Download from Www.Somanuals.com. All Manuals Search And Download.

COM128 Installation and Operation Manual

Schneider Electric

3.2.2

SPEEDCOMPENSATION

APPLICATION

For use with DCE devices that require very accurate baud rate

input. Typical uses are with high speed dial up modems.

This mode can be programmed to either ignore the Carrier

Detect (CD) input of its RS-232 DTE port or require that CD

be asserted by the DCE device before data is transmitted by

the COM128 to the DCE device.

Mode

Port

Baud

SW1

SW2

SW3

SW4

SW5

SW6

Speed Compensation w/o Carrier Detect

DTE

1200

2400

4800

9600

19,200

OFF

Speed Compensation with Carrier Detect

DTE

1200

2400

4800

9600

19,200

OFF

3.2.3

RTS / CTS FLOW CONTROL

APPLICATION

asserted it starts to transmit the buffered data out the RS-232

DTE port. After the last byte in the buffer has been transmit-

ted out the RS-232 DTE port the COM128 de-asserts the RTS

signal and returns to the Idle State.

This mode is used in conjunction with DCE devices which

require hardware RTS / CTS handshaking. Typical uses are

radio modems and multi-drop lease line modems with

switched carriers.

If CTS is not asserted after 256 bytes have been received from

the RS-485 port a buffer overflow will occur. The COM128 de-

asserts RTS and clears the buffer.

RS-232 TO RS-485 DATA FLOW

The COM128 detects the start bit, or falling edge, of the first

byte received by the RS-232 DTE port and sets all 4 RS-485

ports into Transmit mode. The COM128 continues to

monitor the RS-232 DTE port for data and continues to pass

data to the RS-485 port until there is no data coming in the

RS-232 port.

If CTS is not asserted within 256 byte times after the first byte

has been received from the RS-485 port a time-out will occur.

The COM128 de-asserts RTS and clears the buffer.

If CTS is de-asserted before the entire contents of the buffer

have been transmitted out the RS-232 DTE port the COM128

de-asserts RTS and clears the buffer.

RS-485 TO RS-232 DATA FLOW

The COM128 detects data received on any of the 4 RS-485

ports. The first byte is stored in an internal memory buffer

and the Request To Send (RTS) output signal of the DTE RS-

232 port is asserted. The buffer size is 256 bytes. The

COM128 continues to buffer bytes received from the RS-485

port and scans the RS-232 DTE ports' input signal Clear To

Send (CTS). When the COM128 detects that CTS has been

When in the RS-485 to RS-232 Data flow state the COM128

ignores any data received from its' RS-232 DTE port.

Mode

Port

Baud

SW1

SW2

SW3

SW4

SW5

SW6

RTS / CTS Flow control

DTE

1200

2400

4800

9600

19,200

OFF

Download from Www.Somanuals.com. All Manuals Search And Download.

COM128 Installation and Operation Manual

Schneider Electric

monitor the RS-232 DTE port for data and continues to pass

data to the RS-485 port until there is no data coming into the

RS-232 port.

3.2.4

RS-485DATABUFFERINGWITH

TRANSMISSIONDELAYAFTERRTS

ASSERTION

RS-485 TO RS-232 DATA FLOW

APPLICATION

The COM128 detects data received on any of the 4 RS-485

ports. The first byte is stored in an internal memory buffer

and the Request To Send (RTS) output signal of the DTE RS-

232 port is asserted and an internal timer is started. The

buffer size is 256 bytes. The COM128 continues to buffer

bytes received from the RS-485 port. When the COM128's

internal timer has elapsed it starts to transmit the buffered

data out the RS-232 DTE port. After the last byte in the

buffer has been transmitted out the RS-232 DTE port the

COM128 de-asserts the RTS signal and returns to the Idle

State.

This mode is very similar to the RTS / CTS mode. The

COM128 buffers data from the RS-485 ports, asserts its RTS

output then transmits data out of the DTE port after a

programmable time delay. This mode is used in conjunction

with DCE devices which require hardware flow control

(handshaking) but do not provide a CTS signal back to the

COM128. Typical uses are radio modems and multi-drop

lease line modems with switched carriers.

RS-232 TO RS-485 DATA FLOW

The COM128 detects the start bit, or falling edge, of the first

byte received by the RS-232 DTE port and sets all 4 RS-485

ports into Transmit mode. The COM128 continues to

When in the RS-485 to RS-232 Data flow state the COM128

ignores any data received from its' RS-232 DTE port.

Mode

Port

DTE

Baud SW1

SW2

OFF

SW3

OFF

SW4

OFF

SW5

OFF

SW6

RS-485 Data Buffering with 20 mSe c transmission delay after RTS assertion

RS-485 Data Buffering with 50 mSec transmission delay after RTS assertion

RS-485 Data Buffering with 100 mSec transmission delay after RTS assertion

RS-485 Data Buffering with 20 mSec transmission delay after RTS assertion