Omron CJ1W-ECT21 Operation Manual page 38

1 Features and System Configuration
EtherCAT master
Ethernet frame
Ethernet
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Logical process data
Data a
Data b
Data c
Mailbox Communications (SDO Communications)
SDO communications is used to perform message communications.
Whenever necessary, the EtherCAT master sends a command to a slave, and then the slave returns a
response to the EtherCAT master.
The following data communications can be performed.
• Reading and writing process data
• Setting slaves
• Monitoring slave status
1 - 4
Slave Slave
Ether
1st EtherCAT 2nd EtherCAT
CAT
datagram
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CJ-series EtherCAT Slave Units Operation Manual for NJ-series CPU Unit (W542)
Slave
3rd EtherCAT
datagram datagram
Slave
CRC