PowerLogix Computer Accessories COM128 User Manual

PowerLogic® COM128  
RS-232 to RS-485 Converter  
Installation and Operation Guide  
August 2006  
 
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.  
 
Table of Contents  
COM128FEATURES ................................................................................................. 1  
INTRODUCTION ........................................................................................................ 2  
PhysicalFeatures ..................................................................................................... 3  
RS-232Panel ............................................................................................................. 3  
RS-485Panel ............................................................................................................. 3  
CONFIGURATION...................................................................................................... 4  
ConfigurationSwitches ............................................................................................... 4  
ModeDescriptions...................................................................................................... 4  
1
2
2.1  
2.2  
3
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
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  
5
6
SUPPLYING POWER TO THE RS-232 DTR PIN .................................................... 11  
TECHNICALSPECIFICATIONS .............................................................................. 13  
COM128OPTIONS .................................................................................................. 14  
-UNIOption .............................................................................................................. 14  
-INDOption .............................................................................................................. 14  
7
7.1  
7.2  
 
COM128 InstallationandOperationManual  
SchneiderElectric  
TM  
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.  
1
 
COM128 InstallationandOperationManual  
SchneiderElectric  
DTEORDCEOPERATION  
1
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.  
2
 
COM128 InstallationandOperationManual  
SchneiderElectric  
2.2  
RS-485PANEL  
2
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  
3
 
COM128 InstallationandOperationManual  
SchneiderElectric  
Figure 3.1.1  
COM128 Configuration Switches  
3
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.  
1
2
3
4
5
6
ON  
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  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
DTE  
DTE  
DTE  
DTE  
DTE  
1200  
2400  
4800  
9600  
19,200  
OFF  
ON  
OFF  
ON  
OFF  
OFF  
OFF  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
RS-485 Flow Control @ fixed Baud Rate  
DCE  
DCE  
DCE  
DCE  
DCE  
1200  
2400  
4800  
9600  
19,200  
ON  
OFF  
ON  
OFF  
ON  
OFF  
ON  
ON  
OFF  
OFF  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
RS-485 Flow Control with Auto Baud Rate Detect  
DCE  
DTE  
DTE  
DCE  
NA  
NA  
NA  
NA  
OFF  
ON  
OFF  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
OFF  
OFF  
OFF  
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  
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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  
Speed Compensation w/o Carrier Detect  
Speed Compensation w/o Carrier Detect  
Speed Compensation w/o Carrier Detect  
Speed Compensation w/o Carrier Detect  
DTE  
DTE  
DTE  
DTE  
DTE  
1200  
2400  
4800  
9600  
19,200  
OFF  
ON  
OFF  
ON  
ON  
ON  
OFF  
OFF  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
Speed Compensation with Carrier Detect  
Speed Compensation with Carrier Detect  
Speed Compensation with Carrier Detect  
Speed Compensation with Carrier Detect  
Speed Compensation with Carrier Detect  
DTE  
DTE  
DTE  
DTE  
DTE  
1200  
2400  
4800  
9600  
19,200  
ON  
OFF  
ON  
OFF  
ON  
ON  
OFF  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
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  
RTS / CTS Flow control  
RTS / CTS Flow control  
RTS / CTS Flow control  
RTS / CTS Flow control  
DTE  
DTE  
DTE  
DTE  
DTE  
1200  
2400  
4800  
9600  
19,200  
ON  
OFF  
ON  
OFF  
ON  
OFF  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
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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  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
DTE  
Baud SW1  
SW2  
OFF  
OFF  
ON  
SW3  
OFF  
OFF  
OFF  
OFF  
ON  
SW4  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
ON  
SW5  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
OFF  
SW6  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
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  
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  
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  
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  
RS-485 Data Buffering with 50 mSec transmission delay after RTS assertion  
RS-485 Data Buffering with 100 mSec transmission delay after RTS assertion  
1200  
1200  
1200  
2400  
2400  
2400  
4800  
4800  
4800  
9600  
9600  
9600  
OFF  
ON  
OFF  
ON  
ON  
OFF  
ON  
OFF  
OFF  
ON  
ON  
OFF  
ON  
ON  
ON  
ON  
OFF  
ON  
OFF  
OFF  
ON  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
OFF  
ON  
ON  
ON  
ON  
19,200 OFF  
19,200 ON  
19,200 OFF  
OFF  
OFF  
ON  
ON  
ON  
ON  
ON  
ON  
3.2.5  
REPEATER  
Mode  
Port  
Baud SW1  
SW2  
SW3  
SW4  
SW5  
SW6  
For use as a RS-485 repeater. It is a 1 to 3 repeater with Port  
A as a "master" port and Ports B, C, and D as slaves. Ports  
B, C, and D do not share data. The RS-232 ports are not  
used. That is, port A can transmit to B, C, and D, and ports  
B or C or D can transmit to A.  
Repeater  
Repeater  
Repeater  
Repeater  
NA  
NA  
NA  
NA  
1200  
2400  
4800  
9600  
ON  
OFF  
ON  
ON  
OFF  
ON  
ON  
ON  
OFF  
OFF  
OFF  
OFF  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
ON  
OFF  
OFF  
ON  
OFF  
6
 
COM128 InstallationandOperationManual  
SchneiderElectric  
4.2.2  
DIRECTCONNECTION  
TOACOMPUTER  
4
INSTALLATION  
PORT SELECTION  
4.1  
DCSUPPLYCONNECTIONS  
An IBM-compatible PC acts as a DTE (Data Terminal  
Equipment) RS-232 device. Therefore, the computer’s RS-232  
port should be connected to the DCE port on the COM128.  
Refer to Figure 4.2.2.  
The COM128 is shipped with a 9 VDC adapter which plugs  
into the adapter receptacle. Use only the adapter provided  
with the COM128 for this particular powering application.  
Alternatively, any DC power supply capable of supplying  
from 9 to 30 VDC at 500 mA (minimum) can be used to  
power the COM128. Connect the (+) and (-) outputs from  
the power supply to the corresponding terminals of the  
removable 2-pin terminal block connector supplied with the  
COM128 (See Chapter 2, Figure 2.1.1).  
SWITCH SETTINGS  
To properly communicate with the computer, the COM128  
must be configured as a DCE (Data Communications  
Equipment) RS-232 device (see subsection 3.2.1, 'RS-485 Flow  
Control').  
4.2  
RS-232CONNECTIONS  
&CONFIGURATION  
Sections 4.2.2 and 4.2.3 discuss RS-232 port connections  
when connecting to a computer or modem. The COM128  
configuration switches are used to select which port is active.  
Note that the COM128 can also be used in other applications  
by selecting the appropriate port and modes as described in  
Chapter 3. For configuration switch settings, refer to section  
3.2, 'Mode Descriptions'.  
4.2.1  
RS-232CABLE  
A standard RS-232 serial communications cable should be  
used. The COM128 end must be a female DB9 connector for  
direct connection, or a male DB25 for connection via the  
supplied adapter plug. Maximum cable length is 50 feet  
(15.2 m).  
Figure 4.2.2  
RS-232 Direct Connection to Computer  
SHLD  
To  
RS-485  
PORT D  
DCE  
PORT  
RS-232 Cable  
Bus  
PORT C  
50 ft. max.  
DTE  
PORT  
RS-485 Cable  
PORT B  
AWG 22 shielded twisted pair.  
Total length: 4000 ft. maximum.  
PORT A  
COM128  
RS-232 to RS-485 Converter  
IBM PC  
7
 
COM128 InstallationandOperationManual  
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4.2.3  
CONNECTIONTOAMODEM  
PORT SELECTION  
A telephone or radio modem typically acts as a DCE RS-232  
device. Therefore, the modem’s RS-232 port should be  
connected to the COM128’s DTE RS-232 port. Refer to Figure  
4.2.3.  
SWITCH SETTINGS  
To properly communicate with the modem, the COM128 must  
be configured as a DTE RS-232 device .  
If the modem requires RTS-CTS handshaking, the RTS/CTS  
Flow Control function provided by the COM128 should be  
enabled. This will force the COM128 to buffer all RS-485 data  
received until the modem is ready to receive the data. Most  
radio modems require this mode, as do some telephone  
modems. Refer to your modem’s operation manual to see if  
your modem provides or requires this handshaking. .  
Refer to Section 3.2, 'Mode Descriptions', for examples of  
switch settings for this application.  
Figure 4.2.3  
RS-232 Connection to Modem  
RS-232 Cable  
50 ft. max.  
Telephone  
Network, Radio or  
Fibre Optic Link  
Telephone, Radio, or  
Fibre Optic Modems  
IBM PC  
SHLD  
RS-232  
Cable  
50 ft. max.  
To  
RS-485  
Bus  
PORT D  
DCE  
PORT  
PORT C  
DTE  
PORT  
PORT B  
PORT A  
RS-485 Cable  
22 AWG shielded twisted pair.  
Total length: 4000 ft. maximum.  
COM128  
RS-232 to RS-485 Converter  
8
 
COM128 InstallationandOperationManual  
SchneiderElectric  
4.3.3  
RECOMMENDEDTOPOLOGIES  
4.3  
RS-485BUSCONNECTIONS  
CONVERTORCONNECTIONS  
Devices on an RS-485 bus are connected in a point-to-point  
configuration, with the (+) and (-) terminals of each device  
connected to the associated terminals on the next device. This  
is illustrated in Figure 4.3.3a.  
4.3.1  
The RS-485 port of the COM128 provides screw down,  
captured wire type terminal blocks that unplug from the main  
chassis to simplify wiring.  
While there are many topologies that can be used to connect  
devices on an RS-485 communication bus, the two recom-  
mended methods are the straight-line and loop topologies.  
Refer to the following sections for detailed information on  
wiring requirements and recommended topologies.  
STRAIGHT-LINE TOPOLOGY  
The straight-line wiring method is illustrated in Figure 4.3.3a.  
Note that connections are shown for one RS-485 port only. The  
COM128 supports four RS-485 buses simultaneously. The  
COM128 can exist at any position on the RS-485 bus, including  
an end point.  
4.3.2  
GENERALBUSWIRING  
CONSIDERATIONS  
Up to 32 devices can be connected on a single RS-485 bus. The  
overall length of the RS-485 cable connecting all devices cannot  
exceed 4000 ft. (1219 m).  
Each end point of the straight-line bus must be terminated with  
a 1/4 watt resistor. These termination resistors reduce signal  
reflections which may corrupt data on the bus.  
Devices connected on the bus, including convertor(s) and other  
instrumentation, must be wired as follows:  
Termination resistors are connected between the (+) and (-)  
terminals of the device at each end of the bus. This device can  
include either a convertor or any other instrument. The value  
of the resistor should match the line impedance of the cable  
being used. For AWG 22 shielded twisted pair cable, values  
between 150 and 300 ohms are typical. Consult the cable  
manufacturer’s documentation for the exact impedance of  
your cable.  
a. Use a good quality shielded twisted pair cable for each  
RS-485 bus. It is recommended that AWG 22 (0.6 mm) or  
larger conductor size be used.  
b. Ensure that the polarity is correct when connecting to the  
RS-485 port (+) and (-) terminals of each device.  
c. The shield of each segment of the RS-485 cable must be  
connected to ground at one end only.  
LOOP TOPOLOGY  
The loop wiring method is illustrated in Figure 4.3.3a. The  
COM128 can exist at any position on the RS-485 bus.  
CAUTION  
Do not connect ground to the shield at both  
ends of a segment. Doing so will allow  
ground loop currents to flow in the shield,  
inducing noise in the communications cable.  
One advantage of the loop topology is that a single open  
circuit fault condition anywhere on the loop will not result in  
the loss of communication between the computer station and  
any of the remote devices.  
The loop topology does not require termination resistors at any  
point on the bus.  
d. It is recommended that an intermediate terminal strip be  
used to connect each device to the bus. This will allow for  
easy removal of a device for servicing if necessary. The  
terminal strip should be connected as shown in Figure  
4.3.2.  
Figure 4.3.2  
RS-485 Intermediate Terminal Strip Connection  
RS-485  
Device  
Terminal  
Strip  
RS-485 Cable  
22 gauge shielded  
twisted pair  
RS-485PORT  
NOTE  
SHLD  
SHLD  
To next  
device  
Terminal strip connection  
method adds 2 times  
distance X to overall RS-485  
To next  
cable length.  
device  
DISTANCE X  
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COM128 InstallationandOperationManual  
SchneiderElectric  
R S - 4 8 5  
R S - 4 8 5  
RS-232  
RS-232  
10  
 
COM128 InstallationandOperationManual  
SchneiderElectric  
CALCULATING OVERALL CABLE LENGTH  
When determining the overall length of an RS-485 communica-  
tion straight-line or loop connection, it is important to account  
for all cable segments. For example, when RS-485 connections  
to the device are made via an intermediate terminal block  
(Figure 4.3.2), the lengths of cable between the device and the  
terminal block must be added to the total cable distance. This  
length is equal to 2 times distance X in the diagram.  
CONNECTION METHODS TO AVOID  
Any device connection that causes a branch in the main RS-485  
bus should be avoided. This includes star and tee (T) methods.  
Refer to Figure 4.3.3b for examples. These wiring methods will  
cause signal reflections that may cause interference.  
RULEOFTHUMB  
At any connection point on the RS-485 bus,  
no more than two (2) cables should be con-  
nected. This includes connection points on  
instruments, converters, and terminal strips.  
Following this guideline ensures that star  
and tee connections are avoided.  
5
SUPPLYING POWER TO THE  
RS-232 DTR PIN  
The COM128 is shipped configured for use with devices that  
supply their own power.  
Some RS-232 devices, such as short-haul modems and line  
drivers, receive their power from the DTR pin of the RS-232  
line. The COM128 can be configured to support these devices,  
supplying 5 VDC @ 10 mA to the DTR pin of its DTE or DCE  
port.  
To configure the COM128 to supply power on the DTR pin,  
follow this procedure:  
1. Disconnect all power and communications connections to  
the COM128.  
2. Remove the two case screws, and lift the top half of the  
case away from the base of the unit.  
3. Locate the 3-pin jumper blocks J1 and J2. For normal use,  
these are configured with pins 2 and 3 connected. Change  
each jumper so that pins 1 and 2 are connected.  
4. Replace the cover and re-install the screws.  
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COM128 InstallationandOperationManual  
SchneiderElectric  
P
P
 B
PORTA  
P
P
 D
PORTC  
R S - 4 8 5  
R S - 4 8 5  
RS-232  
RS-232  
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COM128 InstallationandOperationManual  
SchneiderElectric  
6
TECHNICAL  
SPECIFICATIONS  
FEATURES  
ELECTRICAL RATINGS  
Baud Rates Supported: 1200, 2400, 4800, 9600, 19200  
Isolation:  
750 V between RS-232 and RS-  
485 ports  
RS-232 Ports:  
One DTE (Male DB9)  
One DCE (Male DB9)  
Power Supply:  
Standard: 9 VDC @ 500 mA  
(120 VAC adapter supplied)  
RS-485 Ports:  
Four 3-pin, pluggable terminal  
blocks, each with (+), (-), and  
shield (SHLD) terminals  
Alternate: 2-pin pluggable terminal  
block accepts  
9-30 VDC  
Power to DTR Pin:  
5 VDC @ 10 mA  
(jumper selectable)  
RS-485 port terminals all pass  
ANSI/IEEE C37.90A-1989  
surge withstand and fast transient tests.  
Operating Temperature: 00C TO 500C (320F to 1220F)  
ambient air  
Storage Temperature: -300C to 700C  
(-220F to + 1580F)  
Humidity:  
5 to 95 percent, non-  
condensing  
Shipping:  
Weight: 0.9 kg (2 lbs. 0 oz.)  
Carton: 30 x 25 x 18cm  
(11.8" x 9.8" x 5.9")  
Figure 6.1  
COM128 Mechanical Dimensions  
5.25"  
(133mm)  
2.13" (54  
mm)  
(includes rubber  
feet)  
5.25"  
(133mm)  
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COM128 InstallationandOperationManual  
SchneiderElectric  
-INDOPTION  
7
COM128 OPTIONS  
The -IND option is a universal power supply that allows the  
COM128 to be powered from any standard international  
voltage and frequency. The power supply is designed for  
industrial applications where it can be mounted on the wall or  
door of a cabinet. Refer to Figure 7.2.1.  
-UNIOPTION  
The -UNI option is a universal power supply that allows the  
COM128 to be powered from any standard international  
voltage and frequency.  
Specifications  
InputVoltage:  
85 VAC to 264 VAC  
110 VDC to 340 VDC  
Specifications  
Input Voltage:  
90 VAC to 264 VAC  
47 Hz to 63 Hz  
Internal Fuse  
InputFrequencyRange: 47 Hz - 440 Hz  
Input Frequency Range:  
Protection:  
Protection: Internalfuse  
OperatingTemperature: 00Cto500C(relativehumidity,non-  
Operating Temperature :  
00C to 400C  
320F to 1040F  
condensing)  
320F to 1220F  
Storage Temperature:  
-400C to 700C  
-400F to 1580F  
StorageTemperature:  
-200C to 750C  
-40F to 1670F  
StandardsCompliance  
The UNI option is CSA and UL approved, and CE compliant.  
STANDARDS COMPLIANCE  
The IND option is CSA, UL and VDE approved, and CE  
certified.  
SPECIALCONSIDERATION  
For the CE certification to be valid, the IND  
power supply must be installed in accor-  
dance with all local electrical codes and  
standards and must not be user-accessible  
during normal operation.  
MechanicalandMountingDimensions  
Dimensions in inches except where otherwise indicated.  
Connections  
The -IND power supply must be connected to a dedicated  
fused feed voltage source. The COM128 is connected to the  
IND supply via the Phoenix 2-pin power supply connector on  
the COM128 enclosure. Refer to Figure 7.2.  
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COM128 InstallationandOperationManual  
SchneiderElectric  
Figure 7.2  
Connecting the -IND Power  
Supply  
COM128  
(see specs for  
for input range)  
1A Slo-Blo  
IND Power Supply  
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COM128 InstallationandOperationManual  
SchneiderElectric  
16  
 
 
 
 
PowerLogic COM 128  
Installation and Operation Manual  
For further assistance  
please contact us at:  
Schneider Electric  
Power Monitoring and Control  
2195 Keating Cross Road  
Saanichton, BC  
Canada V8M 2A5  
Tel: 1-250-652-7100  
295 Tech Park Drive, Suite 100  
Lavergne, TN 37086  
USA  
Tel: 1-615-287-3400  
Electropole (38 EQI)  
31, rue Pierre Mendès France  
F - 38050 Grenoble Cédex 9  
Tel : + 33 (0) 4 76 57 60 60  
Electrical equipment should be installed, operated,  
serviced, and maintained only by qualified personnel.  
No responsibility is assumed by Schneider Electric for any  
consequences arising out of the use of this material.  
Getting technical support:  
Contact your local Schneider Electric sales  
representative for assistance or go to the  
70002-0025-06  
© 2006 Schneider Electric. All rights reserved.  
09/2006  
 

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