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cembeddedmodbus

How the Number of Expected bytes is calculated in Modbus RTU with Function Code 2

i am trying to find out how the Number of expected bytes is calculated with Function Code 2 in Modbus RTU.

I am querying registers from 0 to 71, but as a response i am getting expected bytes as 9 Below is the Query and response.

query : 33 02 00 00 00 47 3C 2A resp : 33 02 09 00 08 00 FE FF FF FF FF 03 FA 68

Solution

  • You queried for 71 bits, the response has 9 bytes containing 8 bits per byte, any excess bits are ignored.