# Modbus TCP Communications

Modbus is a serial client/server protocol developed by Modicon for industrial automation systems. It is one of the oldest industry standard methods for the transfer of discrete and analog I/O information and register data between industrial protocol and monitoring devices.

## Modbus TCP Commands

Note: For more information on this Modbus TCP implementation, see Modbus TCP Factory Interface.

Code | Description | Address Space
--- | --- | ---
0x01 | Read Coils: This function code is used to read the state of 1 to 2000 contiguous coils in a remote device. This command would be used by a PLC to read data from the vision system. | Coil
0x05 | Write Single Coil: This function code is used to write a single output coil to either ON or OFF in a remote device. This command would be used by a PLC to write data to the vision system. | Coil
0x0F | Write Multiple Coils: This function code is used to write a sequence of 1 to 1968 coils to either ON or OFF in a remote device. This command would be used by a PLC to write data to the vision system. | Coil
0x02 | Read Discrete Inputs: This function is used to read the state of 1 to 2000 contiguous discrete inputs in a remote device. This command would be used by a PLC to read data from the vision system. | Discrete Input
0x03 | Read Holding Registers: This function is used to read the contents of a contiguous block of 1 to 125 holding registers in a remote device. This command would be used by a PLC to read data from the vision system. | Holding Register
0x10 | Write Multiple Registers: This function code is used to write from 1 to 123 contiguous registers in a remote device. This command would be used by a PLC to write data to the vision system. | Holding Register
0x04 | Read Input Registers: This function code is used to read from 1 to 125 contiguous input registers in a remote device. This command would be used by a PLC to read data from the vision system. | Input Register