1 - 3
1 EtherCAT Network
GX-series EtherCAT Slave Unit User’s Manual
1-1 Overview of EtherCAT
Networks
1
1-1-2 Structure of EtherCAT
It is the "EtherCAT datagram" stored directly in an Ethernet frame that exchanges data regularly
between the EtherCAT Master Unit and Slave Units.
Each "EtherCAT datagram" is configured with header (data length, including address of one or more
Slave Units, etc.), data, working counter (check bit).
When an Ethernet frame is compared to a "train", an EtherCAT datagram can be considered as "railway
car."
Ethernet
header
CRC
Ethernet data (Maximum 1498 bytes)
Data
Header
WKC
1...n EtherCAT datagram
EtherCAT
header
1st EtherCAT
datagram
2nd EtherCAT
datagram
n th EtherCAT
datagram
. . . . .
EtherCAT frame
Ethernet frame
WKC : Working counter