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5 EtherCAT Communications
GX-series EtherCAT Slave Unit User’s Manual
5-
4 Process D
ata Obje
cts (
P
D
O
)
5
5-
4-1 Overview
5-4 Process Data Objects (PDO)
The process data objects (PDO) are used for real-time data transfer via cyclic communications.
There are two types in PDO: RxPDO that receives data from the EtherCAT Master Unit and TxPDO that
sends the present value from a EtherCAT Slave Unit to the EtherCAT Master Unit.
It is possible to hold multiple objects in the EtherCAT application layer so that various process data of
EtherCAT Slave Units can be transferred. The details of process data are described in PDO Mapping
Objects and Sync Manager PDO Assignment Objects.
GX-series EtherCAT Slave Units support PDO mapping for I/O control.
The PDO mapping indicates the mapping for application objects (realtime process data) between the
object dictionary and PDO.
The number of mapped objects is described in sub-index 0 of the mapping table. In this mapping table,
indexes 1600 hex to 17FF hex are used for RxPDO and 1A00 hex to 1BFF hex are used for TxPDO.
5-4-1 Overview
5-4-2 PDO Mapping Settings
RxPDO
output data, operation command, and so on
TxPDO
input data, status, and so on
EtherCAT
Master
Unit
EtherCAT
Slave
Unit