Modbus is a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices. Modbus is popular in industrial environments because it is openly published and royalty-free.
It was developed for industrial applications, is relatively easy to deploy and maintain compared to other standards, and places few restrictions on the format of the data to be transmitted. The Modbus protocol uses character serial communication lines, Ethernet, or the Internet protocol suite as a transport layer.
Modbus supports communication to and from multiple devices connected to the same cable or Ethernet network. For example, there can be a device that measures temperature and another device to measure humidity connected to the same cable, both communicating measurements to the same computer, via Modbus. Modbus communication checking is often required between PLC and DCS or two PLCs or between PLC and a Computer.
It is often difficult to understand communication by using Application software of PLC/DCS. That is why there are number of tools that are available in market to check the modbus communication. In this video, we have shown two free tools Modbus Poll and Modbus Slave. We have also demonstrated how the modbus TCP/IP communication is happening between them. You can download these two software from here: