The master device then waits for the answer. With the Unicast variant, a request is sent from the master to the slave. These are known as Unicast and Broadcast. The Modbus RTU protocol enables two communication variants. The Communication Procedure of the Modbus RTU Protocol This includes for example sensors, controllers, and actuators.Īlready for quite some time, production automation as well as process automation fall back to the protocol, which represents the basis of digital networks in the network installation hierarchy. Use of the Modbus RTU InterfaceĪs an open protocol, Modbus RTU enables the connection of field devices via serial interfaces (RS-485 or RS-232). Enterprises increasingly use optical waveguides to create an increase in the transfer capacity. A power line carrier (PLC) serves for transfer of control data on a high-voltage line. The control center and the RTU interface communicate either wirelessly or via a so-called pilot cable. It thus becomes possible to perform control, checking, and monitoring of individual processes from a control center.

The RTU interface is used in energy distribution, energy generation, energy transmission, and in process engineering. The RTU interface thus becomes a control-based or control instrument. The Modbus RTU interface (RTU = Remote Terminal Unit) makes it possible to set up a remote operation or remote maintenance terminal. Although each participant may send messages, sending is normally initiated by the master and only answered by a slave. Modbus also shows differences in regard to the data transfer.Īccordingly, we can distinguish between the following operation modes:Īs each communication participant can send messages via the bus, each of them must receive a corresponding and unique address. With this, the two available versions of Modbus refer to the Ethernet and the serial interface (EIA-232 & EIA-485). The open Modbus protocol enables communication between one master and several slaves.

As an open protocol, Modbus has found its way into industrial communication and is being used there as ubiquitous de-facto standard for programmable logic controllers. The Modbus protocol is a communication protocol based on the master-slave principle, which was developed by Gould-Medicon.

Modbus rtu serial communication protoco