The integral part of industrial automation is PLC (Programmable Logic Control). It has become an evolution in the field of industrial automation. PLC enables the enhancement and fastest development of automation industry. The data communication in an automated network is enabled by means of communication standards or protocols. This article is all about one of the oldest and commonly used communication protocols in PLC.
What is a communication protocol?
There will be several devices connected in a PLC network. Basically, the data communication between these devices are by means of communication protocols. Device to device data transfer is made possible by the use of industrial standard protocols. One of the commonly used protocols is Modbus.
Basics of Modbus
Modbus is one of the popular communication protocols in industrial automation. It is an open standard that uses physical media such as RS232/485 or ethernet.
The process of communication via modbus is through master-slave approach. The slave devices receive the data signals from master devices and act accordingly and also communicate the result with the supervisory control sector. The figure below shows the Modbus RTU(Remote Terminal Unit).
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Pros and Cons
A Modbus network can incorporate many devices such as PLC, process controls, PID controls, motor drives, valves, SCADA systems etc within the system. The flexibility and adaptability of the Modbus protocol enhance its wide range of applications in the industrial networks.
The maximum number of slave devices is 247. This is a limitation of the Modbus networking structure. Also, the amount of configuration and programming required in Modbus network is very high.
History of Modbus
Modbus is developed and launched by Modicon in 1979. Schneider Electric has the ownership of Modicon today.
Knowledge of the Modbus network is very essential for any technical person working in the field of industrial automation. Also, engineers and technicians with the ability to integrate Modbus structural network is of great demand in today's technological world.
