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1   EtherCAT Network
E3NW-ECT EtherCAT Digital Sensor Communication Unit Operation Manual (E429)
1-1  Overview of EtherCAT
Networks
1
1-1-2  Structure of EtherCAT
It is the "EtherCAT telegram" stored directly in an Ethernet frame that exchanges data regularly 
between the EtherCAT Master Unit and Slave Units. 
Each "EtherCAT telegram" is configured with telegram 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 telegram can be considered as "railway 
car."
 Ethernet
header
CRC
 Ethernet data (Maximum 1498 bytes)
Data
Telegram
header
WKC
 1...n EtherCAT telegram
EtherCAT
header
 1st EtherCAT
telegram
2nd EtherCAT
telegram
n th EtherCAT
telegram
. . . . .
 EtherCAT frame
 Ethernet frame
WKC : Working counter