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Chapter 5 EtherCAT Communication
Overview of EtherCAT bus
EtherCAT is a high-performance, low-cost, easy-to-use and topologically flexible industrial Ethernet technology that
can be used for ultra-fast I/O networks at the industrial field.
Standard physical layer of Ethernet, with transmission media of twisted pairs or optical fibers (100 Base-TX or 100
Base-FX).
EtherCAT system consists of a master station and several slave stations. The master station only requires a common
network card, while slave stations require special chips for slave control, such as ET1100、ET1200、FPGA.
EtherCAT is real time down to the I/O level:
No underlying sub-systems any more
No delays in gateways
All devices are included in one system:
－ Inputs and outputs, sensors, actuators, drives, displays...
Transmission speed:
－ 2 x 100 Mbit/s (high-speed Ethernet, full duplex)
Synchronization: up to 300 nodes are between two devices with the cable length of 120 m, but the jitter is less
than 1 us
Update time (in typical application):
－ 256 digital I/O in 11 us
－ 1000 digital I/O distributed to 100 nodes in 30 us = 0.03 ms
－ 200 analog I/O (16 bit) in 50 us, 20 kHz sampling rate
－ 100 servo axis (each 8 Byte IN + Out) in 100 us = 0.1 ms
－ 12000 digital I/O in 350 us
To support a wider range of devices and application layers, EtherCAT establishes the following application protocols:
－ CoE (CANopen application protocol based on EtherCAT)
－ SoE (Servo drive conventions according to IEC 61800-7-204)
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