Precautions for Correct Use
If you use synchronous I/O refreshing, set the task period of the periodic task as follows.
• A value within the specified refresh cycle range of the High-speed Analog Input Unit
• A value larger than the NX bus refresh cycle that is automatically calculated by the Support
Software
Also refer to the user's manual for the connected CPU Unit or EtherCAT Coupler Unit for infor-
mation on setting the task periods of periodic tasks.
5-2-4
I/O Refreshing Operation
This section describes the operation of synchronous I/O refreshing that the High-speed Analog Input
Units support. It also describes the sampling operation of the High-speed Analog Input Units.
The following describes the method of synchronous I/O refreshing.
• The timing to read inputs or to refresh outputs is synchronized on a fixed interval between more than
one NX Unit connected to a CPU Unit.
• The timing to read inputs or to refresh outputs is synchronized on a fixed interval between more than
one NX Unit on more than one Slave Terminal.
The operation of I/O refreshing in the CPU Unit and that in the Slave Terminal are given below.
CPU Unit Operation
The following describes the operation of synchronous I/O refreshing between an NX-series CPU Unit
and the NX Units.
• All NX Units that are connected to the CPU Unit and operate with synchronous input refreshing read
their inputs at the same time at a fixed interval based on the synchronization timing. (Refer to (a) in
the figure below.)
• The High-speed Analog Input Units perform conversions in order to obtain the input values of the
final analog input data sampled, before the timing to read inputs.
The timing of starting the AD conversion in the first sampling is the same for all channels of the
High-speed Analog Input Unit. (Refer to (b) in the figure below.)
Similarly, for all channels of the High-speed Analog Input Unit that perform the same number of
samplings, the timing of starting the AD conversion in the second and later samplings is the same.
(Refer to (c) in the figure below.)
• The CPU Unit reads the analog input values, which are read by the Unit at the timing of reading
inputs, at immediate I/O refreshing. (Refer to (d) in the figure below.)
• The interval of I/O refreshing varies with the processing conditions of the CPU Unit. (Refer to (e) in
the figure below.) The timing to read inputs will be at a fixed interval. (Refer to (f) and (g) in the fig-
ure below.)
• The timing of reading inputs, the synchronization timing, and the maximum NX bus I/O refresh cycle
are automatically calculated by the Support Software according to the input refresh cycles of the NX
Units on the CPU Unit when a Unit configuration in the CPU Unit is created and set up.
5 I/O Refreshing
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NX-series Analog I/O Units User’s Manual for High-speed Analog Input Units (W592)
5-2
I/O Refreshing Methods
5
5-2-4
I/O Refreshing Operation
