EtherCAT: The Real-Time Fieldbus

EtherCAT: High-Performance Industrial Communication

EtherCAT (Ethernet for Control Automation Technology) is a real-time Ethernet communication protocol developed by Beckhoff Automation. It offers superior performance compared to any other fieldbus for motion control applications.

Working Principle

EtherCAT uses a unique principle called "processing on the fly":

1. The master sends a single Ethernet frame through the network
2. Each slave (encoder, drive, I/O) reads its own data and inserts its response into the frame WHILE the frame passes through it
3. The last slave sends the frame back to the master
4. A complete cycle for 100 nodes requires only ~100 μs

Topology

• Line (daisy-chain): each device has two RJ45 ports (IN and OUT). Ethernet cable passes from one to the next.
• Star, tree, ring: supported via EtherCAT switches or junctions
• Distance between nodes: up to 100 m with standard Cat.5e Ethernet cable

Performance

• Cycle time: < 100 μs for hundreds of nodes
• Jitter: < 1 μs (deterministic)
• Bandwidth: 100 Mbit/s (full duplex)
• Synchronization: Distributed Clocks (DC) with < 100 ns jitter between slaves

Italsensor EtherCAT Encoders

Italsensor encoders with integrated EtherCAT (TSM-ETHCAT and TSML-ETHCAT series) implement the CoE (CAN over EtherCAT) profile with:

• Single-turn (13-bit) and multi-turn (14-bit) absolute position
• Internally calculated speed
• Configurable position preset
• Complete diagnostics (internal temperature, bearing status, errors)
• Distributed Clocks for multi-axis synchronization

Advantages for Automation

1. Simple wiring: single Ethernet cable for data + power (with EtherCAT P)
2. Integrated diagnostics: each encoder reports its health status
3. Remote parameterization: resolution, preset, direction configurable from PLC
4. Industry 4.0: direct integration with SCADA and MES systems
5. Cost reduction: no dedicated encoder cable, no SSI module in PLC

Compatible EtherCAT Masters

• Beckhoff TwinCAT: native integration
• Siemens S7-1500: via EtherCAT slave module
• Codesys: EtherCAT master runtime
• Linux: open-source EtherCAT master (IgH)