Archive for the ‘Modbus/TCP’ Category

Modbus – Introduction

Monday, June 15th, 2009

Modbus has achieve interoperability in building automation systems is Modbus. The Modbus protocol was developed during the 1970s by Modicon, Inc. for use in industrial automation systems with programmable controllers. Today it is one of the most widely used means for connecting electronic equipment in industrial applications. Its simplicity is also making it a useful tool for achieving interoperability in building automation applications.

Modbus consists of a messaging structure designed to establish master-slave, client-server communications between a wide range of intelligent devices. It supports traditional serial and Ethernet protocols. It is a truly open standard and is one of the most widely used protocols in the industrial manufacturing environment. There is no charge for using the protocol nor are there licensing fees. Tools and resources that can be used to expedite installation and support operations are available on-line.

The original version of Modbus included two transmission modes: ASCII and RTU. More recently, Modbus/TCP was developed, allowing the Modbus protocol to be transmitted over TCP/IP based networks.

In 2004, the standard was transferred to Modbus-IDA. Modbus-IDA is a nonprofit organization made up of users and suppliers of automation devices primarily in manufacturing.

While Modbus was initially designed for use in industrial applications, its use has rapidly spread to building automation, transportation, and energy applications. Its strengths include openness, simplicity, and minimum hardware requirements. Another significant benefit is the protocol’s use of the TCP/IP transport protocol, the same protocol used by the Internet. This means that Modbus can readily be used over the Internet.

Modbus does have a certification process to ensure conformance to their standard. However, in spite of the widespread use of the Modbus protocol, only a fraction of the installations have gone through the certification process.