Implementing Modbus TCP

Almost all implementations have variations from the official standard. Different varieties may not communicate correctly between different suppliers equipment. Some of the most common variations are:

Data Types

  • Floating Point IEEE
  • 32 bit integer
  • 8 bit data
  • mixed data types
  • bit fields in integers
  • multipliers to change data to/from integer. 10, 100, 1000, 256 …

Protocol extensions

  • 16 bit slave addresses
  • 32 bit data size (1 address = 32 bits of data returned.)
  • word swapped data

« Back Next »