Hi guys,

I am connecting a PLC (ICP Con) to a Citect SCADA via a Modbus TCP-Serial Converter (Westermo EDW100). The PLC is configured as a Slave (via Modbus RTU) and Citect is a Client (via Modbus TCP). The Citect is connected to the PLCs via 2 network lines (redundancy). There is a Modbus converter on each line. The functionality of this system is fine and all data can be sent/monitored from Citect...

My problem is I am unable to do any error processing on the Citect in the event that any PLC is down. I need help to "talk" to the Modbus converter from Citect to know if any of the PLCs (Slaves) are down/non-functional... Can this be done? Is there any C-code that I can incorporate into Citect to interface to the Modbus converter?

Thanks...

 

Just use the built in CiCode functions: IODeviceInfo() or CitectInfo() to return the status of the Standby IODevices that you have defined in your project.

Cheers,
Nathan Slider

 

The gateway should respond with an exception code 11 (0x0B) Gateway target device failed to respond. This lets the TCP/IP driver know that the remote serial device is down or unaccessible.

An OPC server that is talking to the remote device would then mark the data quality for the items on that device as bad. It should also have a status variable for the devices that indicates it is not communicating.

Fred Loveless
Senior Application Engineer
Kepware Technologies
http://www.kepware.com