Hi,

I have come across a modbus function code of 20 hex coming from a Modicon Momentum. Anyone know of why the function code would be 20 hex? I am unable to find this code anywhere.

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Thanks aggattapauer, but I have been through this documentation a dozen times. As you can see, there is no function code 20 hex. The exact modbus message I am getting is "3E 20 1D 14 C7 FF"

The 3E hex makes sense, because i am trying to poll modbus address 62, but i cannot find why the function code would be 20 or why it would try to send that. Any suggestions?

Could you show me also your modbus request?

Could you describe the system architecture?

The type of Momentum? Which application is Master modbus?

I have posted the modbus request above

Basically, I have a wonderware application which collects data from a data concentrator. The data concentrator, the Modicon Momentum, sends polls the multiple RTU's via radio to collect data from each. The above posted request is sent out by the data collector to the RTU's. Currently, the RTU's are Modicon Micro's. They seem to handle the request just fine. The Siemens S7-200 does not recognize the request.

I am not sure what type of Momentum is there, I am making a return trip tomorrow (The system is 2 hours from our office). I am going to record the modbus request post modem at the data concentrator and and post modem at the remote test station.