# Supported Modbus RTU function codes

Supported methods for reading or writing Modbus RTU data items.

Operation | Size | Data source | Function name | Function code
--- | --- | --- | --- | ---
Read | 1 bit each | Application program | Read Coils | FC 1
1 bit each | External | Read Discrete Inputs | FC 2
16 bit each | Application program | Read Holding Registers | FC 3
16 bit each | External | Read Input Registers | FC 4
Write | 1 bit | Application program | Write Single Coil | FC 5
16 bit | Application program | Write Single Register | FC 6
Write | 1 bit each | Application program | Write Multiple Coils | FC 15
Write | 16 bit each | Application program | Write Multiple Registers | FC 16