Omron GRT1-ECT SmartSlice, Operation Manual

Page: 26 / 142

1 EtherCAT Network
1 - 4 GRT1-series EtherCAT Communication Unit - Operation Manual
EtherCAT provides the following two types of communication types.
PDO communications are always updating data per communication cycle on EtherCAT, while SDO
communications are processed in between those updates.
The PDO communication function is used to transfer process data in real time in a fixed-cycle.
By mapping logical process data space to each node by the EtherCAT Master Unit, it achieves
fixed-cycle communication among the EtherCAT Master Unit and Slaves.
Communication with Service Data Objects (SDO) refers to message communication.
At any timing, the EtherCAT Master Unit transmits commands to Slaves and the Slaves return
responses to the EtherCAT Master Unit.
It performs the following data communication:
• Read and write process data
• Make Slave setting
• Monitor Slave state
1-1-3 Communication types of EtherCAT
Process Data Communication functions (PDO communication)
Mailbox communication functions (SDO communication)
EtherCAT Master Unit
Slave Unit
Ethernet frame
Slave Unit Slave Unit
Slave Unit
Ethernet
header
EtherCAT
header
1st EtherCAT
telegram
2nd EtherCAT
telegram
3rd EtherCAT
telegram
CRC
. . .
Logic process data
.
.
.
.
.
.
.
.
.
Data a
Data b
Data c