Types Of Ethercat Communications - Omron CJ1W-ECT21 Operation Manual

1 Features and System Configuration
Ethernet frame
Ethernet
Ethernet data (1,498 bytes max.)
CRC
header
1
1st to nth EtherCAT datagrams EtherCAT frame
EtherCAT
header
1st EtherCAT 2nd EtherCAT . . . . .
nth EtherCAT
datagram datagram
datagram
Header Data WKC
WKC: Working counter
1-1-2

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.
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CJ-series EtherCAT Slave Units Operation Manual for NJ-series CPU Unit (W542)