Omron GRT1-ECT SmartSlice, Operation Manual

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2 EtherCAT Communication details
2 - 2 GRT1-series EtherCAT Communication Unit - Operation Manual
2-1 Structure of CAN application protocol
over EtherCAT (CoE)
Multiple protocols can be transferred by EtherCAT. The GRT1-series EtherCAT Communication Unit
uses "CAN application protocol over EtherCAT (CoE)". CoE is a communication interface for EtherCAT
devices, as the device profile of the open network standard "CAN application protocol".
The figure below shows the structure of CoE in the GRT1-series EtherCAT Communication Unit.
The CAN application protocol has a data object dictionary.
There are two types of data objects in this dictionary:

Process Data Objects (PDO)
• Contains Process data
• Composed of objects that can be mapped.
• The process data is defined by PDO mapping.
• PDO is primarily used in PDO communication for cyclic exchange of process data.

Service Data Objects (SDO).
• SDO are used in non-cyclic type SDO (event type messages) communication.
EtherCAT Slave Unit
EtherCAT physical layer
Communications
status transitions
SDO (mailbox)
Slave application
Object dictionary
PDO mapping
PDO (cyclic)
EtherCAT data link layer
Registers Mailbox Process data
FMMU SyncManager
Application layer