What is Modbus RTU and Modbus TCP?

ModbusCommunicationRS485EthernetProtocol

What is Modbus?

Modbus is a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its Programmable Logic Controllers (PLCs). Due to its simplicity, reliability, and open-source (royalty-free) nature, it has become a de-facto standard for connecting industrial electronic devices. It uses a Master/Slave architecture, where one device (the Master) manages the line and sends queries to one or more devices (Slaves).

Modbus RTU (Serial)

Modbus RTU typically operates over serial communication using the RS-485 or RS-232 physical layers. Data is encoded in a binary format, allowing for fast and compact transmission.

  • Advantage: It works reliably over long distances (up to 1200 meters) and in environments with high electrical noise.
  • Application: Sensors, drives, temperature controllers.

Modbus TCP (Ethernet)

Modbus TCP is the adaptation of the Modbus protocol to run over TCP/IP networks. It uses the standard Ethernet physical layer.

  • Advantage: Much higher speeds, ability to use existing network infrastructure, and remote access over the internet.
  • Application: SCADA systems, HMI panels, advanced automation networks.

Amazeng GDT Series Digital Transmitters can integrate easily into any automation infrastructure with support for both Modbus RTU and Modbus TCP.

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