Hot Topic: GTNETx2 Modbus Protocol

Hot Topic: GTNETx2 Modbus Protocol

New Modbus Protocol for the RTDS? Dinomite!

Stegosaurus, Triceratops, Tyrannosaurus Rex… These were some of the most famous dinosaurs that still roamed the earth when the Modbus protocol was originally introduced… Okay, maybe I am exaggerating just a little bit… But if you’re a strapping young lad such as myself, then Modbus was probably a little bit before your time.


Modbus Protocol

Originally introduced in the late-70s by Modicon, (14 years before the first Jurassic Park movie) Modbus was originally used to link other smart devices with PLCs. Since then, Modbus has become an open protocol which means that manufacturers are free to incorporate it into their equipment without having to pay royalties.  Having stood the test of time, Modbus is still widely used today with over 7 million Modbus nodes reported in North America and Europe alone. Modbus is often praised for its unrivaled simplicity, which is quite evident from the fact that its specification is only a mere 50 pages long!

The Modbus protocol uses the familiar master/slave concept by which the designated master has full control over the communication bus. The master will record outputs and read inputs from each of the slaves who will only respond when requested too by the master. If no such request is made, then the slaves simply sit idle. Today, Modbus is commonly used in SCADA and system automation based applications to facilitate communication between a master station and a RTU. (Remote Terminal Unit)

Previously, only the Modbus master station could be implemented within RSCAD software by using the scripting facility within Runtime. However, with the introduction of the new Modbus component and communication protocol for the GTNETx2, it is now possible to implement a Modbus slave within RSCAD software.


The new ­Modbus component allows for Modbus communication over TCP/IP networks by using a GTNETx2 card configured with the Modbus protocol. More specifically, the component supports three different variants of the Modbus protocol, namely,

  1. Modbus TCP
  2. Modbus RTU over TCP, and
  3. Modbus ASCII over TCP

This new functionality now allows users to interface and test an external Modbus master with the RTDS Simulator.

Be sure to check out the new Modbus component and GTNETx2 protocol in the latest release of RSCAD! Should you have any questions, please do not hesitate to contact us at

Author: Christian Jegues
May, 2017