Applies To:
  • CitectSCADA 5.xx
  • CitectHMI 5.xx

I would like Citect to communicate to my SLC5/03 using the KE500 driver, and using the built in RS232 (CH0) port. But I note that the KE driver is only half duplex, meaning that my RSLinx RS232 connection does not work anymore. Is there any way to have both Citect and RSLinx communicate with the SLC5/03 in Half Duplex mode? 

Yes. It is possible to communicate to the SLC5/03 using both RSLinx and CitectSCADA using half duplex DF1 protocol via the built in RS232 port.

Firstly lets setup the PLC channel configuration and RSLinx:

By default the SCL5/03 has the following CH0 parameters; 1200 Baud, 8 data bits, 1 stop bit, no parity, Full Duplex, and BCC error checking. These settings do not exactly give the high performance a system might need, so lets increase the baud rate to 19200, use CRC error checking, and use half duplex so that it is compatible with CitectSCADA and the KE driver.

Using RSLogix, configure the Channel 0 - System RS232 port with the following settings:

Driver: DF1 Half Duplex Slave
Baud: 19200
Parity: None
Source ID: 1 (Decimal)
Error Detection: CRC

Now download the configuration. You will note that once you write the channel configuration you will no longer be able to use RSLinx with the default driver configuration (RS232 DF1 device).

It is no longer possible to let RSLinx Autodetect your settings, it will fail to find the appropriate settings.

Open RSLinx and Configure a new RS232 DF1 Device (you may need to remove or stop the old configuration). Use the following settings to get RSLinx communicating using DF1 Half Duplex Slave:

Comm port: COM1 (or any other serial port you may have)
Device: 1770-KF3/1747-KE
Baud rate: 19200
Parity: None
Stop bits: 1
Error Checking: CRC
Station Number: 1 (Decimal)
Protocol: Half Duplex

Click OK to this configuration (Note: Auto-configure will not work!!!!). You should now have successful communications using RS232 DF1 Half Duplex.

Also note, that you can use other baud rates, depending on your RS232 connection. It is recommended that 19200 be used with a maximum cable length of 10m, otherwise communication could become unreliable.

Now setup CitectSCADA with the following settings.

IOServer Configuration:
IOServer Name: IOServer
Board Configuration:
IOServer Name: IOServer
Board Name: Board1
Board Type: COMX
Address: 0
Port Configuration:
IOServer Name: IOServer
Port Name: Port_1
Number: 1 (This is the COM port number)
Board Name: Board1
Baud Rate: 19200
Data Bits: 8
Stop Bits: 1
Parity: NONE
IODevice Configuration:
IOServer Name: IOServer
Name: SLC503
Number: 1
Address: 1 -CRC
Protocol: KE500
Port Name: Port_1

This configuration was successfully achieved using the following versions of Software:

CitectSCADA 5.50r0

RSLinx 2.41

RSLogix 500 5.20

KE Driver

Windows 2000 SP4

And the following Harware:

SLC 5/03 (1747-L351)

Null Modem cable (RX, TX crossed over)

Note: This configuration is also valid for SLC5/04, and SLC5/05 using the built in RS232 port.