Function Codes Supported by Modbus RTU Slave

The Modbus RTU Slave Communications option supports the Modbus function codes listed in the following table. As well, the maximum number of coils or registers that may be specified or included in a single Modbus message is also given.

Function Code Description Maximum # of coils / registers
1 Read Coil Status 2000
2 Read Input Status 2000
3 Read Holding Registers 125
4 Read Input Registers 125
5 Force Single Coil 1
6 Force Single Register 1
15 (0x0F) Force Multiple Coils 800
16 (0x10) Preset Multiple Registers 100