Omron ZW-C1*AT User Manual page 162

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
EtherCAT
header
1st EtherCAT 2nd EtherCAT
datagram
Header
160
EtherCAT Connection
Ethernet frame
Ethernet data (Maximum 1498 bytes)
1...n EtherCAT datagram
datagram
Data
. . . . .
n th EtherCAT
WKC
WKC : Working counter
CRC
EtherCAT frame
datagram
ZW User's Manual