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Wago 750-8204 vs Wago 750-8214 Modbus RTU Master

4 days ago
  • happychappy

    happychappy - 2022-04-20


    I am using Codesys V3.5 SP17 (64Bit) and I am experiencing the following issue:

    I download my program to a 750-8204 CPU (Modbus Master) that communicates to a Slave Modbus PSU. When I select the modbus master, it shows the Bus is running but when I select the modbus slave device, it shows timeout, and I can see the counter incrementing for requests that is being sent out.

    However when I connected RS485 to USB as a slave on the Modbus network I do not see the Master transmitting any data.

    When I download that exact program to a 750-8214 CPU, immediately the RS485-USB converter detects activity on the Modbus network and I could see the slave devices reacting.

    Is there something on the hardware side of the PLC of the older Wago models that requires more software setup to work?

    See attached pictures of the results when the program is on 750-8204

  • somlioy

    somlioy - 4 days ago

    Shouldnt be any difference ...
    Are they running the same FW aswell?

    I'd expect it to be an configuration issue since the Port can behave as RS232, 422 or 485.
    Also verify that there is no owner assigned to the serial port on WBM.


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