NP5 ModbusRTU Online Manual

General

Modbus is generally big-endian based.

The only exceptions are the commands with function codes 43 (2Bh), 101 (65h) and 102 (66h), which are based on CANopen. For the data values of these commands, the little-endian format applies. The remainder of the Modbus message is, on the other hand, based on big-endian.

Example

Command 2Bh: With this command, the value 12345678h is written in object 0123h (does not exist):

SA
Slave address
FC
Function code
Data
Data range, decoding is dependent on the used function code
CRC
Cyclic redundancy check
▶   next

Contents