HMI Pad Forums Old forum Common Support Requests (old) Modbus Exception 0B

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  • #20039

    John
    Keymaster

      Good morning. I am trying to use SM-one (to see if this works for me) on one of our large battery storage units. I can access the holding registers with other products, but am having trouble with SM-One (probably user error). Example is SOC, register 560 decimal. My csv file is:

      # %protocol modbus/tcp
      SOC_Value,UINT,HR560,”section=”"modbus/tcp”"; label=”"Battery SOC”";”

      This returns “Modbus Gateway target device failed to respond (modbus exception 0B)”.

      I am certain there is a value at this register, verified with another product. Any suggestions would be appreciated.

      #20040

      John
      Keymaster

        This message implies communications were fine and your controller responded with a correct modbus error frame (exception 0B). However It is not clear what this means in the case of your PLC.

        Something to take into account is that ScadaMobile uses the Modbus Specification convention for registers so it considers numbering starting at 1, so first register is HR1, not HR0. This differs from modbus addresses as they always start by 0, so maybe you just need to offset your register number by one (i.e HR561 instead of HR560) in case 560 actually refers to a modbus address instead of a modbus register.

        Please also look at the manual of your controller to determine what could cause a modbus exception 0B in your controller response, this very possibly will give you a hint on what is going on.

        Thanks.

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