1. What is Modbus?

Modbus is a communications protocol created by Modicon(currently Schneider Electric) in 1979 and was created for use in communication with Programmable Logic Controller(PLC) used to automate and control the machines in manufacturing plants.

It is simple, but it has become a standard protocol because it can perform necessary functions for equipment control and monitoring.

The features of Modbus, the industrial communication protocol, can be summarized as follows.

  • Open protocol (free)
  • Easy to install and maintain
  • Easy to manipulate information in units of Bit or word (16 bits)

Modbus is a protocol based on master/slave basically. For example, you can have several devices that measure temperature and humidity report their current status to the monitoring server.

Modbus is mainly used to connect the monitoring server and remote terminal unit (RTU) in SCADA(Supervisory Control And Data Acquisition) system.

Modbus can be divided into Modbus RTU/ASCII available for serial communication and Modbus TCP available for Ethernet communication.

Modbus RTU uses serial communication network and uses binary information in the frame. Modbus ASCII also uses serial communication network but communicates with ascii characters in the frame. In other words, if you put 0, ASCII code of 0 which is 48 will occupy one byte in the actual frame.

 

  1. Modbus gateway?

The Modbus gateway is a converter that supports these protocols. When a Modbus RTU/ASCII signal is received, it is converted to Modbus TCP, and on the contrary, when a Modbus TCP signal is received, it is converted to Modbus RTU/ASCII and exported.

Connecting a Modbus gateway to any serial-based devices allows you to control or monitor remotely by connecting to an Ethernet network.

modbus_gateway_wiz2000

<Modbus gateway communication>

 

WIZnet plans to release a Modbus gateway (or Modbus converter) that supports the Modbus protocol.

modbus_gateway_wiz2000-2

<The modbus gateway (WIZ2000-MB) that is in development>