5 I/O Refreshing
5 - 12
NX-series Analog I/O Units User’s Manual for Analog Input Units and Analog Output Units (W522)
The I/O refreshing method described below. Among Slave Terminals, only EtherCAT Slave Terminals
support this refreshing method.
• The timing to read inputs is synchronized on a fixed interval between more than one NX Unit con-
nected to a CPU Unit.
• The timing to read inputs is synchronized on a fixed interval between more than one NX Unit on more
than one Slave Terminal.
This method is used when the problem such as input timing jitter or offset of timing to read inputs
between more than one NX Unit happens.
z CPU Unit Operation
The following describes the operation of synchronous input refreshing between the NX-series
NX1P2 CPU Unit and the NX Units.
• All Digital Input Units and Analog Input Units that are connected to the CPU Units 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 Analog Input Units perform AD conversion once for each refresh cycle of the NX bus in order
to obtain the AD converted values of all inputs for which the used channels are set to enable at the
time to read inputs.
AD conversion is performed in order from the lowest channel number, so that the timing to convert
is different for each input.
• The CPU Unit reads the input values, which are read by the Unit at the timing of reading inputs, at
immediate I/O refreshing. (Refer to (b) in the figure below.)
• The interval of I/O refreshing varies with the processing conditions of the CPU Unit. (Refer to (c) in
the figure below.) The timing to read inputs will be at a fixed interval. (Refer to (d) and (e) in the
figure below.)
• The timing of reading inputs, the synchronization timing, and the maximum NX bus I/O refresh
cycle are automatically calculated by the Sysmac Studio 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.
5-2-5 Synchronous Input Refreshing
Description of Operation
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