01. Introduction
In the previous article, we mentioned that Modbus TCP is a low-real-time fieldbus, while EtherCAT is a high-real-time industrial Ethernet protocol.
The Modbus protocol was once widely used in the early era of industrial automation. However, with the rapid development of automation technologies, EtherCAT has gradually replaced Modbus in many application scenarios and has become the preferred communication protocol for high-performance control systems.
This article explains in detail why EtherCAT has replaced Modbus, and explores the application scenarios in which this transition has occurred.
02. Basic Concepts
To understand this transition, we first need to review the fundamentals of both protocols.
Modbus is a serial communication protocol originally published by Modicon (now Schneider Electric) in 1979.
It is a simple and easy-to-implement protocol mainly used to connect industrial electronic devices. Modbus uses a request-response communication model in which a master device sends requests and slave devices return responses. One master can communicate with multiple slaves.
Modbus supports several communication media such as RS-232, RS-485, and TCP/IP.
It has two major transmission modes:
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Modbus RTU (Remote Terminal Unit) — for serial communication
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Modbus TCP (Transmission Control Protocol) — for Ethernet communication
Modbus is mainly used to connect industrial equipment such as PLCs, controllers, and sensors.
Its primary advantages are simplicity and ease of use, but its communication speed and real-time performance are relatively limited.
EtherCAT (Ethernet for Control Automation Technology), developed by Beckhoff Automation in Germany in 2003, is a real-time Ethernet protocol based on a master-slave architecture.
The master sends a continuous data frame, and each slave device processes its data on the fly and forwards the frame to the next device. EtherCAT features high speed, strong real-time capability, and precise synchronization, making it ideal for demanding motion-control and automation systems.
03. Why EtherCAT Has Replaced Modbus
The replacement of Modbus by EtherCAT is primarily due to the following key factors:
1. Speed and Performance
EtherCAT’s communication speed is significantly higher than that of Modbus.
EtherCAT supports 100 Mbps and even 10 Gbps, whereas Modbus typically operates at only tens or hundreds of kilobits per second.
EtherCAT’s much greater throughput allows it to handle large volumes of I/O data efficiently—an essential advantage in high-speed automation applications.
2. Real-Time Capability and Determinism
EtherCAT provides deterministic real-time communication, ensuring predictable data exchange cycles.
Modbus, in contrast, cannot guarantee strict timing.
Applications such as motion control and robotics, which demand sub-millisecond synchronization, benefit greatly from EtherCAT’s nanosecond-level Distributed Clock synchronization mechanism.
3. Network Topology and Scalability
EtherCAT supports flexible and scalable topologies, including line (daisy-chain), star, tree, and ring configurations.
This allows complex system layouts and multi-node communication without performance loss.
Modbus, on the other hand, is typically limited to point-to-point or simple master-slave serial architectures, making large-scale integration more difficult.
4. Compatibility and Interoperability
EtherCAT is built on standard Ethernet technology, enabling seamless integration with existing Ethernet infrastructure.
Modbus often requires dedicated hardware and drivers, resulting in limited compatibility.
EtherCAT also demonstrates better interoperability with other real-time Ethernet standards, simplifying system integration and expansion.
5. Safety
Modbus lacks inherent security mechanisms such as encryption or authentication, leaving it vulnerable to cyberattacks and data tampering.
EtherCAT addresses this through the Safety over EtherCAT (FSoE) protocol, certified by TÜV to comply with IEC 61508 SIL 3 standards for functional safety in process data transmission.
6. Diagnostics and Maintenance
Because Modbus uses a request-response mechanism, troubleshooting often requires device-by-device communication, which can be time-consuming.
EtherCAT provides comprehensive diagnostic and maintenance features, allowing the master to monitor and localize faults across the entire network.
Functions such as break detection, precise error localization, and logical diagnostics make EtherCAT much more efficient in industrial maintenance environments.
7. Cost and Ease of Use
While Modbus devices have lower unit costs, their wiring and maintenance expenses can be higher due to limited communication efficiency.
EtherCAT, although technically superior, is now cost-competitive thanks to the mass production of domestic EtherCAT Slave Controller (ESC) chips such as ET1100 and ET1200 equivalents.
As more manufacturers adopt EtherCAT, its ease of implementation and technical support ecosystem have improved dramatically.
04. Application Scenarios Where EtherCAT Replaces Modbus
Typical scenarios where EtherCAT has replaced Modbus include:
1. High-Speed Production Lines
Modern high-speed production systems demand fast and deterministic communication between devices.
EtherCAT delivers the required speed and timing accuracy, where Modbus would create bottlenecks.
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| (Semiconductor manufacturing processes using EtherCAT networks.) |
2. Motion Control
Motion-control applications require high-precision and low-latency communication.
EtherCAT’s short cycle times and high data throughput make it ideal for servo drives and multi-axis motion controllers, replacing Modbus in most advanced systems.
3. Robotics
Robotics systems demand precise synchronization across multiple actuators and sensors.
EtherCAT enables microsecond-level synchronization, ensuring smooth coordinated motion — a major reason many robot OEMs have shifted from Modbus to EtherCAT.
4. Industrial Automation Systems
Large-scale automation projects often require flexible topologies and easy scalability.
EtherCAT’s support for various network structures allows simple system expansion, making it the preferred choice for smart factories and Industry 4.0 systems.
5. Data Acquisition and Monitoring
Applications such as magnetic levitation control and vision inspection require extremely fast data acquisition.
EtherCAT’s high throughput and deterministic timing outperform Modbus, enabling accurate real-time monitoring and control.
05. Conclusion
In the field of industrial communication, Modbus has played a foundational role for decades, providing a reliable and simple solution for device connectivity.
However, as Industry 4.0 and smart manufacturing evolve, communication protocols must meet higher demands for speed, determinism, scalability, and security.
With its real-time performance, high speed, flexible topology, and broad compatibility, EtherCAT has become the preferred protocol in many modern automation environments.
That said, Modbus remains valuable in simple control and data acquisition applications where its simplicity and low cost suffice.
We pay tribute to Modbus for its long-standing contribution to industrial communication —
and look forward to EtherCAT driving the next generation of high-performance, intelligent automation systems.