ABB PLC communication thru Modbus

Hi everyone.

I have a problem in my current project. I am using 4 ABB PLC PM-583 and plan to use Modbus to communicate and integrate them to my graphics. However, there seems to be a problem with my communication. I can communicate with each individual PLC through Codesys but when I use Modbus to communicate with each other, the communication terminates.

I have tried 1 to 1 communication with each PLC and use Modscan to verify my Modbus communication. But after 1 valid poll and response the Modbus communication terminates.

Can anybody shed any light on where I might have missed out?

Thanks!

What plc? its usually a good idea to string your modbus messages together...modbus rtu ot tcp. I think we need more detail

Hi, thank you for the reply.

I'm using ABB brand PLC. My CPU model is PM-583. Yes, I did a mapping of all my modbus points. I am sure that there is no conflict or duplicated address.

As stated, I can communicate to each PLC 1 to 1 through the programming tool Codesys. I can directly send commands and read the inputs in the Codesys. But when I use the modbups communication to communicate my PLC with my graphics, it terminates after 1 valid poll and 1 valid response.

I tried to download the program again, changed my CPU, changed my rack, built again the program from scratch, but still the communication terminates.

I assume your CODESYS is your MASTER and your ABB are slaves. So your OP are set as MASTERS to?

I don't believe CoDeSys uses Modbus. What is your graphics controller? Modbus has to be set up in the PLC. You need to both configure it using Control Builder Plus, and you need to map your variables to modbus addresses within CoDeSys. There is no inherent Modbus comms in the ABB PLC, everything has to be mapped.