Modbus is one of the popular communication protocols in modern automation. This is the oldest protocol that is still trusted by many businesses thanks to its easy-to-use interface, affordable price, and outstanding efficiency.

The Modbus protocol has many outstanding features and a wide range of applications, making it easy to integrate single devices. In this article, let’s learn more about Modbus with Flextech.

What is Modbus used for?

Modbus is a popular communication protocol in the automation industry, and it is widely used in industrial applications thanks to its simplicity, flexibility, and effective connection between devices. Some typical applications of Modbus are:

• Connecting to I/O Devices: this protocol can connect to most I/O devices, from simple devices to complex systems, supporting effective data transmission between sensors, controllers, and variable frequency drives.
• Connecting to PLC: Modbus is used to connect to PLCs, including PLC lines such as Series 7, Series 1000, Modicon TSX Micro, Premium, Quantum, Momentum, Compact, and plays an important role in transmitting data between PLCs and peripheral devices.
• Telemecanique Equipment: These devices typically include controllers, actuators, converters, and smart sensors, which optimize the control and monitoring of production processes using the Modbus protocol.

What are the advantages and disadvantages of using Modbus in industry?

Advantages

Modbus is a widely used and trusted protocol in many automation fields thanks to its outstanding features such as:

• Simple and efficient architecture: Modbus has an easy-to-understand structure, making it quick and easy to deploy and integrate into industrial automation systems.
• High reliability: Modbus operates stably, especially in applications that require accuracy and reliability in communication.
• Flexibility in connection: Modbus RTU provides efficient communication over serial connections, while Modbus TCP provides high speed and can connect multiple devices over Ethernet, with no limit on the number of devices.
• No licensing costs: This protocol will help save costs because it does not require licensing, reducing the total cost of deployment.

Disadvantages

In addition to its outstanding advantages, the Modbus protocol still has some limitations that users need to pay attention to:

• Limited diagnostics: Modbus has limited fault diagnosis capabilities and does not support many tools to detect communication problems.
• Requires independent power sources: Modbus RTU devices require their own power sources, adding cost and complexity to powering the devices.
• Limited to complex data types: Modbus is often not designed to support complex data types or large binary objects well, making it difficult to handle modern data-intensive applications.
• Master-slave architecture is not suitable for bilateral communication: Master-slave architecture may not be effective in applications that require simultaneous communication between multiple devices, so the processing capacity will be limited in environments with complex communication requirements.

What types of Modbus are there?

Modbus is generally classified into three main types: Modbus RTU, Modbus RS-485, and Modbus TCP/IP.

Modbus RTU

• The protocol uses binary coding and CRC error checking.
• Transmits data via a serial connection, with speed from 1,200 to 115,200 bit/s.
• Suitable for short to medium distances, easy to install, and low cost.
• Limited on distance and number of connected devices.

Modbus RS-485

• Using RS-485 communication standard, allowing long-distance data transmission (up to 1,200m).
• Supports multiple devices on one line, good anti-interference ability.
• Speed ​​is adjustable and ideal for applications requiring long-distance communication.
• Complex configuration and maximum speed may be affected by distance.

Modbus TCP/IP

• Runs on Ethernet networks, allowing unlimited connections of devices via IP addresses.
• High transmission speed and easy integration into industrial network systems.
• Suitable for large networks and long distances, but requires high network infrastructure and technical knowledge.

How does Modbus work?

Modbus is a popular protocol in industrial environments due to its features such as being publicly available and royalty-free, easy to implement and maintain, and having few restrictions on data formats. It is specifically designed for industrial applications.

Modbus operates over serial communication lines, Ethernet, or Internet protocol suites as its transport layer, allowing Modbus to connect and transmit data between multiple devices on the same Ethernet cable or network.

The most obvious example is that a temperature-measuring device and a humidity-measuring device can be connected to the same network or cable, and both devices will send data to the same computer. Modbus enables these devices to communicate efficiently and easily share information, creating a flexible automation network in industrial applications.

What does Modbus’s basic architecture consist of?

A complete Modbus protocol usually has a structure consisting of 4 main components: device address, function, data, and error-checking code:

• Device address: This is the device identification code in the network, each device will have a separate address to receive and send messages.
• Function: Supports the description of the action that the device needs to perform, such as reading data, writing data, or changing the device’s state.
• Data: The part that contains information or values ​​that need to be transmitted between devices, such as sensor values, control signals, etc.
• Error checking code: Ensures that the transmitted data is error-free. This code checks the accuracy of the data that has been sent.