Introduction To I/O Refreshing For Ethercat Slave Terminals - Omron NX-ECC201 User Manual

10 I/O Refreshing
10-1 Introduction to I/O Refreshing for
EtherCAT Slave Terminals
This section introduces I/O refreshing for NX-series EtherCAT Slave Terminals.
The NJ-series CPU Unit performs I/O refreshing cyclically with the NX Units in an EtherCAT Slave Ter-
minal through EtherCAT communications and the NX bus.
The following four cycles affect the operation of I/O refreshing between the NJ-series CPU Unit and the
NX Units in an EtherCAT Slave Terminal.
(A) Task period of the primary periodic task of the CPU Unit (called the primary period)
(B) Process data communications cycle
(C) Refresh cycle of the NX bus
(D) Refresh cycle of each NX Unit
The following figure shows the operation of I/O refreshing when the built-in EtherCAT port on the
NJ-series CPU Unit is used for communications with an EtherCAT Slave Terminal.
• The (B) process data communications cycle and (C) refresh cycle of the NX bus are automatically
synchronized with the (A) primary period of the CPU Unit.
• The (D) refresh cycles of the NX Units depend on the I/O refreshing method of each NX Unit. You can
also use synchronous I/O refreshing for some NX Units and Free-Run refreshing for others. For infor-
mation on the I/O refreshing methods of the NX Units, refer to 10-3 I/O Refreshing for EtherCAT
Slave Terminals on page 10-6.
*1. This applies when the distributed clock is enabled in the EtherCAT Coupler Unit.
NJ-series CPU Unit
(A) Primary period
Built-in EtherCAT port
EtherCAT Slave Terminal
Example: Synchronous I/O refreshing
10 - 2
I/O refreshing between the CPU
Unit and NX Units
(B) Process data communications cycle
EtherCAT NX Unit NX Unit
Coupler Unit
(C) Refresh cycle of the NX bus
Example: Free-Run refreshing
*1
NX Unit
Other EtherCAT slaves
(D) Refresh cycle of
each NX Unit
Example: Synchronous I/O refreshing
NX-series EtherCAT Coupler Unit User's Manual (W519)
Communications path