Flow Ctrl Tech Engineering

Modbus 32-Bit Floating Point Word Swapping: Big-Endian vs Little-Endian Decoding

Solve garbled numerical readings in PLC and SCADA systems: converting IEEE 754 32-bit floats across two 16-bit Modbus registers, CDAB vs ABCD byte orders, and bitwise parsing.

  • The original Modbus specification only defines 16-bit registers; 32-bit float encoding is manufacturer-dependent.
  • The four primary permutations are ABCD (Big Endian), CDAB (Word Swap / Mid-Little Endian), BADC (Byte Swap), and DCBA (True Little Endian).
  • Always test numerical scaling by reading known static calibration registers (such as frequency setpoint or manufacturer model ID).

Flow Ctrl Tech Engineering: Turnkey industrial automation, PLC programming, SCADA development, HMI, fieldbuses, and IIoT architectures. Contact our engineering center at [email protected] or phone +91 91110 91005.