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How can we use the M221 to read UINT32 and FLOAT32 data types out of a Power meter PM5300?

FA275098

30 September 2021

Symptoms:
  • If you use the READ_VAR at address 130 with quantity = 1 you will get an error : CommError = 254 and OperError = 3.
  • If you change the quantity = 2 you will still get the same error : CommError = 254 and OperError = 3: You will get the high order byte in %MW130 = 0 and lower order byte in %MW131 = 0.
The general register list for the Power meters gives you the Jbus addressing registers and not the Modbus addressing registers.
Jbus addressing starts at n and the Modbus addressing then should be n -1.
  • If you now use the READ_VAR at address 129 (n -1) with quantity = 1 you will get the same error : CommError = 254 and OperError = 3.
  • If you change the quantity = 2 life is good: You will get the high order byte in %MW130 = xxxx and lower order byte in %MW131 = xxx.