Types Of Ethercat Communications - Omron NX-ECC201 User Manual

1 EtherCAT Networks
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Types of EtherCAT Communications

The following 2 types of communications are available with EtherCAT.
PDO communications are executed in each EtherCAT communications cycle to refresh data continu-
ously. SDO communications are executed between PDO communications.
Process Data Communications (PDO Communications)
PDO communications transfers process data cyclically and in realtime.
The EtherCAT master maps the logical process data space to the nodes to achieve cyclic communica-
tions between the EtherCAT master and slaves.
EtherCAT master
Ethernet frame
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
Ether
Ethernet 1st EtherCAT
CAT
header telegram
header
Slave Slave
2nd EtherCAT 3rd EtherCAT
telegram telegram
NX-series EtherCAT Coupler Unit User's Manual (W519)
Slave
CRC