Synchronous I/O Refresh Cycle - Omron NX-ECC201 User Manual

9 Setting Up Slave Terminals
For example, if the _sNXUNIT_ID variable NXUnitC is assigned to NX Unit C in the above figure, the
program would not need to be corrected even if the Unit configuration changed as long as the array
subscript is specified with NxReg[NXUnitC.UnitNo].
For information on how to register variables to assign to Units and how to assign variables, refer to the
NJ-series CPU Unit Software User's Manual (Cat. No. W501-E1-06 or later).
Additional Information
NX Unit Mounting Settings
If an NX Unit is removed or if you know in advance that an NX Unit is planned to be added, you
can use the NX Unit mounting settings to prevent the NX Unit numbers from changing.
Refer to 11-2 NX Unit Mounting Settings on page 11-5 for details on the NX Unit mounting set-
tings.
9-6-2

Synchronous I/O Refresh Cycle

When you use synchronous I/O refreshing, the refresh cycle on all other Slave Terminals will increase
when the refresh cycle for any one Slave Terminal increases.
The refresh cycle of a Slave Terminal increases in the following cases.
• If you add an NX Unit with a long refresh cycle to a Slave Terminal, the synchronous I/O refresh cycle
will greatly depend on the refresh cycle of that NX Unit.
• If the number of NX Units mounted to a Slave Terminal increases, the amount of data communica-
tions increases and the communications path within the Slave Terminal becomes longer. Therefore,
the cycle that enables synchronization of I/O becomes longer.
To eliminate the influence of the refresh cycles between NX Units on a Slave Terminal and between
Slave Terminals, use Free-Run Mode to operate all Slave Terminals that do not require synchronous
I/O refreshing.
Additional Information
• Refer to 10-3-2 Setting the I/O Refreshing Methods on page 10-6 for the setting procedure of
the I/O refreshing method.
• With synchronous I/O refreshing, the same refresh cycle is used between the NX Units on
the same Slave Terminal and between NX Units on different Slave Terminals.
Therefore, the synchronous I/O refresh cycle depends on the refresh cycle of the NX Unit
with the longest refresh cycle of all of the NX Units that use synchronous I/O refreshing.
9 - 42
NX-series EtherCAT Coupler Unit User's Manual (W519)