Modbus protocol: description and scope of application


Modbus is one of the most common communication standards. This protocol is popular because it is open. Today manufacturers of industrial monitoring and management systems produce devices supporting Modbus networks. 90% of the equipment has special drivers for working with this protocol. Let`s consider in more detail the history of the standard, its basic principles and areas of use.

What should I know about Modbus?

The developer of the standard is the company Modicon. The first specification was released in 1979. The protocol is based on one of the most common communication models: Master/Slave. It connects electronic devices to different networks. It is also called an application protocol. It does not operate in the physical layer. It is designed for data transmission via RS-232/422/485. The Modbus TCP modification involves the exchange of information over a TCP/IP network. The protocol also has a less common implementation for communication over UDP.

The protocol is widely used in various industries. Modbus can rightly be called a communication standard, as it is built into equipment by Russian and foreign manufacturers. The main function of the protocol is serial communication: transmission of signals from control devices to the main controller. The Master sends a message with necessary requests to the Slave. The Slave sends responses to the Master. In a simplified form, the message format looks like this:

    • device address,
    • function code,
    • information,
    • grand total.

Modbus OPC Server

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