Modbus Connection


Modbus is a communication protocol used primarily for industrial automation systems and devices. Developed in 1979, it enables communication between electronic devices such as Programmable Logic Controllers (PLCs), sensors, and actuators, using a master-slave structure. Modbus is widely used due to its simplicity, open-source nature, and compatibility with various devices and networks.

Key Takeaways

  1. Modbus is a communication protocol that allows devices to exchange data by establishing a client-server relationship. It was developed by Modicon in 1979 for use with its programmable logic controllers (PLCs).
  2. It operates on two transmission modes: Modbus ASCII and Modbus RTU. Modbus ASCII uses human-readable characters, while Modbus RTU uses a more compact binary representation, which enables faster communication and better error detection.
  3. Modbus is widely used in various industries due to its simplicity, open-source nature, and compatibility with different devices. It facilitates communication between various automation equipment such as sensors, actuators, and controllers, allowing for efficient and reliable data sharing.


Modbus is an important technology term because it represents one of the most widely used and established communication protocols for industrial automation and control systems.

Developed in 1979, Modbus has allowed devices from different manufacturers to communicate effectively over various mediums such as serial lines and Ethernet networks.

This robust and easy-to-implement protocol facilitates seamless data exchange between programmable logic controllers (PLCs), sensors, actuators, and other devices essential for monitoring and controlling complex industrial processes.

By providing a common standardized platform for diverse equipment to interact with each other, Modbus has played a crucial role in driving industrial efficiency and productivity, as well as fostering interoperability and integration.


Modbus is a communication protocol primarily used in the realm of industrial automation and control systems, functioning as the bridge that enables communication between a centralized computer (typically referred to as the “master” device) and various electronic devices such as sensors, actuators, and other industrial equipment, which are regarded as the “slave” devices. Established in 1979 by Modicon, Modbus was designed to simplify the process of data exchange between devices and allow them to seamlessly communicate, even when sourced from different manufacturers.

This highly versatile and widely accepted protocol serves a critical purpose in industries such as manufacturing, energy, water treatment, and building automation, making it easier for organizations to monitor and manage multiple devices and variables in their respective operations. The essence of the Modbus protocol lies in the way it structures, transmits, and processes data, achieved through its widespread support of two main forms of communication: Modbus RTU (Remote Terminal Unit) and Modbus TCP/IP (Transmission Control Protocol/Internet Protocol). While Modbus RTU employs a serial connection and communicates in binary form over wired networks, Modbus TCP/IP uses Ethernet as the basis for its communication, allowing it to capitalize on the ubiquitous nature of modern internet infrastructure.

Despite the nuances in their communication approach, both formats adhere to a consistent register-based data representation, enabling the master device to send messages (or commands) to slave devices, requesting information or urging them to perform certain tasks. Real-world applications of Modbus include monitoring energy production in solar power plants, tracking the condition of industrial equipment, managing heating, ventilation, and air conditioning (HVAC) systems, as well as controlling water treatment processes.

Examples of Modbus

Modbus is a communication protocol used in industrial automation systems, and its primary purpose is to transmit and receive data between devices in real-time. Here are three real world examples of Modbus applications:

Building Automation Systems: Modbus is used in building automation systems, such as HVAC controls, lighting controls, and energy management systems, to enable communication between devices like temperature sensors, thermostats, and ventilation systems. This helps in streamlining and optimizing energy consumption and maintaining a comfortable environment inside the building.

Water Treatment Plants: In water treatment plants, Modbus can be used to connect several devices like water level sensors, pressure sensors, valves, and pumps, allowing them to share and exchange data with the central control system. This enables efficient monitoring and control of the entire water treatment process, ensuring safe and clean water supply.

Factory Automation: In manufacturing and industrial plants, Modbus can be used to enable communication between various machines and equipment, like conveyor belts, robotic arms, and assembly lines. This helps in monitoring and controlling the production process, reducing human intervention, and increasing overall efficiency and productivity.

Modbus FAQ

1. What is Modbus?

Modbus is a serial communication protocol originally developed in 1979 for connecting electronic devices. It is now a widely accepted and commonly used protocol for communication between industrial electronic devices. Modbus allows communication between multiple devices connected to the same network and is often used for connecting sensors, instruments, and other devices to a central computer.

2. How does Modbus work?

Modbus uses a master-slave or client-server architecture. The master or client initiates communication by requesting data or issuing a command to the slave device. The slave device then responds with the requested information or performs the requested action. Modbus can operate over several types of transmission media, including serial lines and Ethernet networks.

3. What are the different types of Modbus protocols?

There are primarily two major types of Modbus protocols: Modbus RTU and Modbus TCP/IP. Modbus RTU is a binary protocol that uses serial communication to transmit data, while Modbus TCP/IP is an adaptation of the protocol that uses Ethernet networks for communication.

4. What are some common applications of Modbus?

Modbus is used in various industries for a wide range of applications, including industrial automation, building automation, HVAC, renewable energy, and transportation. It is commonly used for data acquisition, control, and monitoring of equipment and processes.

5. What are the advantages of using Modbus?

Some advantages of using Modbus include its simplicity, ease of use, wide adoption, and support for a large number of devices. It is also flexible, allowing for communication over different types of transmission media, and is cost-effective compared to some other communication protocols.

Related Technology Terms

  • Modbus Protocol
  • Modbus TCP/IP
  • Modbus RTU
  • Modbus Master/Slave
  • Modbus Registers

Sources for More Information

  • Modbus Organization – Official organization that manages and supports Modbus protocol
  • Schneider Electric – A leading manufacturer of industrial automation equipment, including Modbus devices
  • ProSoft Technology – Offers a wide range of Modbus communication solutions and resources
  • Control Engineering – A popular industry magazine that frequently covers Modbus technology and applications

Technology Glossary

Table of Contents

More Terms