Modbus is a fieldbus serial communications protocol published by Modicon (now Schneider Electric) in 1979, originally for use with its programmable logic controllers (PLCs). It is now commonly used for connecting industrial electronic devices.
Modbus TCP is a version of the Modbus RTU protocol which uses the TCP/IP interface of an Ethernet network.
Modbus RTU is used to daisy-chain devices in a network with serial communication. It is very popular for industrial control networks as it is well established, and there is a wide variety of hardware and software that supports it.
Speedgoat provide high performance I/O modules for Modbus TCP (see Selection Guide below). Support for Modbus RTU is provided by external gateways. All solutions come with Simulink driver blocks.