Omron NX-ECC201 User Manual page 222

10 I/O Refreshing
Additional Information
The EtherCAT Slave Terminals with enabled distributed clocks and all EtherCAT slaves that
support DC synchronization execute I/O processing based on Sync0, which is shared on the
EtherCAT network. Because EtherCAT Slave Terminals and EtherCAT slaves have different
specifications and performance levels for the timing of reading inputs and updating outputs, the
timing of reading inputs and updating outputs are not the same for them.
Operation of Free-Run Refreshing
With Free-Run refreshing, the refresh cycle of the NX bus and the I/O refresh cycle of the NX Units
operate asynchronously.
NX Unit #4 in EtherCAT Slave Terminal #3 in the figure labeled Example of I/O Refreshing Method
Operation on page 10-9 provides an example of operation with Free-Run refreshing.
The NX Units perform I/O processing based on their own unique timings ((C) and (D) in the figure),
independent of Sync0.
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NX-series EtherCAT Coupler Unit User's Manual (W519)