Master devices obtain information from slaves and can also write in their registers. A Modbus RTU master is a central device that makes request for information from the connected slave devices. In instrumentation and distributed automation, Modbus is mainly programmed in 'RTU' mode to allow the connection between supervision systems (SCADA, Supervisory Control and Data Acquisition) and remote terminal units (RTU, Remote Terminal Unit). Although it has been designed for serial data exchange, over the years, several variants (RTU, ASCII, TCP, Plus) have been created in order to make it more suitable for multiple communication channels. The Modbus protocol is a system that processes requests and responses from electronic devices based on a master / slave architecture which is used for master-slave communications. The most common fieldbus is still Profibus which holds 10% of the world market but is followed by Modbus RTU with a 5% share. Certainly, the industrial communication market sees a growing predominance of Ethernet, Wireless and IoT technologies, but traditional fieldbuses keep a huge installed capacity and represent 35% of new nodes installed (HMS Network 2019 study). The wide availability of libraries and the low cost of implementation also encourages the use of Modbus in internal networks of medium and high complexity systems.

Its success is due to its royalty-free and hardware independent nature, toughness, ease of implementation, availability of specifications that have allowed its use in a wide variety of areas such as distributed automation, process control, energy monitoring, remote control, building automation and plant supervision.

The Modbus protocol is the oldest and most widespread serial fieldbus. International in the RTU version.īorn back in 1979 within Modicon (now a brand of Schneider Electric) the Modbus protocol is still one of the most popular serial communication systems between PLC, DCS, controllers, sensors, actuators, field devices and interfaces. Because it is open source and royalty-free, it is widely used by manufacturers to connect software and electronic devices. Modbus is a de facto standard for industrial communication protocols.

Modbus rtu serial communication protoco