modbus applications
Using MODBUS for
Process Control and Automation
MODBUS is the most popular industrial protocol being used today, for good reasons. It is simple, inexpensive, universal and easy to use. Even though MODBUS has been around since the past century—nearly 30 years— almost all major industrial instrumentation and automation equipment vendors continue to support it in new products.
Although new analyzers, flowmeters and PLCs may have a wireless, Ethernet or fieldbus interface, MODBUS is still the protocol that most vendors choose to implement in new and old devices.
Figure 1. A MODBUS RTU network consists of one “master,” such as a PLC or DCS, and up to 247 “slave” devices connected in a multi-drop configuration.
MODBUS RTU Master
MODBUS RS485
Twisted Wire Pair
NET Concentrator System
Station #1
Another advantage of MODBUS is that it can run over virtually all communication media, including twisted pair wires, wireless, fiber optics, Ethernet, telephone modems, cell phones and microwave. This means that a
MODBUS connection can be established in a new or existing plant fairly easily. In fact, one growing application for MODBUS is providing digital communications in older plants, using existing twisted pair wiring.
In this white paper, we’ll examine how MODBUS works and look at a few clever ways that MODBUS can be used in new and legacy plants.
What is MODBUS?
MODBUS was developed by Modicon (now Schneider
Electric) in 1979 as a means for communicating with many devices over a single twisted pair wire. The original scheme ran over RS232, but was adapted to run on
RS485 to gain faster speed, longer distances and a true multi-drop network. MODBUS quickly became a de facto standard in the automation industry, and Modicon released it to the public as a royalty free protocol.
Today, MODBUS-IDA (www.MODBUS.org), the largest organized group of MODBUS users and vendors, continues to support the MODBUS protocol worldwide.
MODBUS
Process Control and Automation
MODBUS is the most popular industrial protocol being used today, for good reasons. It is simple, inexpensive, universal and easy to use. Even though MODBUS has been around since the past century—nearly 30 years— almost all major industrial instrumentation and automation equipment vendors continue to support it in new products.
Although new analyzers, flowmeters and PLCs may have a wireless, Ethernet or fieldbus interface, MODBUS is still the protocol that most vendors choose to implement in new and old devices.
Figure 1. A MODBUS RTU network consists of one “master,” such as a PLC or DCS, and up to 247 “slave” devices connected in a multi-drop configuration.
MODBUS RTU Master
MODBUS RS485
Twisted Wire Pair
NET Concentrator System
Station #1
Another advantage of MODBUS is that it can run over virtually all communication media, including twisted pair wires, wireless, fiber optics, Ethernet, telephone modems, cell phones and microwave. This means that a
MODBUS connection can be established in a new or existing plant fairly easily. In fact, one growing application for MODBUS is providing digital communications in older plants, using existing twisted pair wiring.
In this white paper, we’ll examine how MODBUS works and look at a few clever ways that MODBUS can be used in new and legacy plants.
What is MODBUS?
MODBUS was developed by Modicon (now Schneider
Electric) in 1979 as a means for communicating with many devices over a single twisted pair wire. The original scheme ran over RS232, but was adapted to run on
RS485 to gain faster speed, longer distances and a true multi-drop network. MODBUS quickly became a de facto standard in the automation industry, and Modicon released it to the public as a royalty free protocol.
Today, MODBUS-IDA (www.MODBUS.org), the largest organized group of MODBUS users and vendors, continues to support the MODBUS protocol worldwide.
MODBUS