What is Modbus TCP?

In previous articles, I told you about different communication protocols. Today, I will try to explain to you simply ModBUS, which is a different communication protocol. Let's get to know ModBUS TCP.

What is Modbus TCP Protocol?

Modbus is a serial communication protocol developed by Modicon in 1979 for use with PLCs. Modbus TCP/IP uses TCP/IP and Ethernet to transport Modbus message structure data between compatible devices. So, Modbus TCP/IP is a standard method of representing a physical network (Ethernet) and data with a network standard (TCP/IP). A Modbus TCP/IP message is simply a Modbus communication encapsulated in an Ethernet TCP/IP packet.

The Modbus protocol uses a Master/Slave technique to communicate between devices. That is, any application that uses the Modbus protocol will have a Modbus Master and at least one Modbus Slave. A Modbus Master is usually a host controller computer that will communicate with one or more Modbus Slave devices.

What are the ModBUS protocol types?

• Modbus RTU Modbus RTU protocol uses serial communication protocols arranged according to master/slave architecture. It is widely used due to ease of use and reliability. Simplicity and reliability are ensured with the 16-bit CRC (error control mechanism) used for the secure transmission of messages sent in two-bit data.

• Modbus ASCII In the Modbus network structure, it is based on the way data is communicated using 8-bit coding according to the ASCII coding system. The advantage of this coding is that it allows data sent consecutively to be transmitted without causing an error. Using LRC error checking, it is checked whether more than 8 bits of data are sent.

• Modbus Plus This protocol, developed by Schneider and Modicon, is connected to a global Fieldbus network. It is used in PLC, drivers and many peripheral devices. It is used in industrial applications with the PLUS RS-485 communication protocol, which works based on the master/slave structure. In addition to high-speed data transmission, it has a flexible structure.

• Modbus TCP/IP Protocol It is a simple-to-use protocol designed for supervision and control of automation devices. This protocol, which provides communication according to the classical internet network topology, transfers data at a speed of 100 Mbps with standard internet cards. Many connections can be made with the TCP/IP protocol. A connection is established between the server/client devices and data transfer occurs. While any device can be a client or server, there can be many servers or clients in the system. In the TCP/IP protocol, the data transmission speed varies depending on the processor and internet card type used in the devices.

What is Slave ID?

Each Slave in a network has its own address number, ranging from 1 to 247. When the Master requests data, the Slave's address information is the first byte sent. Thus, each Slave knows after the first byte whether to ignore the message.

What is Function Code?

The second byte sent by the master is called function code. These numbers tell the Slave the table to access and whether to read or write to it.

Today, I tried to briefly explain the ModBUS communication protocol to you. I hope you made it this far without getting bored. I will continue to share about automation and industry. Please don't forget to follow and subscribe.

If you liked my article, I am waiting for your comments and votes. Finally, don't forget to check out my past articles to learn more.

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