Free-Run Refreshing - Omron NX-ID3343 User Manual

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Free-Run Refreshing

With this I/O refreshing method, the refresh cycle of the NX bus and I/O refresh cycles of the NX Units
are asynchronous.
Digital I/O Units read inputs or refresh outputs at the time of I/O refreshing.
This method is used when it is not necessary to be aware of factors such as the I/O timing jitter and the
concurrency of the timing to read inputs and refresh outputs between the NX Units.
Description of Operation
• You can connect the following NX Units to the Slave Terminal to use this method.
The NX Units that support Free-Run refreshing
• The Communications Coupler Unit performs I/O refreshing for NX Units in order. (Refer to (a) in the
figure below.)
• The NX Units read inputs or refresh outputs at the time of I/O refreshing. (Refer to (b) in the figure
below.)
• The Communications Coupler Unit can read the most recent input value at the time of I/O refreshing
and the NX Units can control the most recent output value at the time of I/O refreshing. However,
since I/O refreshing is performed in order, timing to read inputs or to refresh outputs for each NX Unit
in the Slave Terminal does not occur at the same time. (Refer to (c) in the figure below.)
• The interval of I/O refreshing varies with the processing conditions of the Communications Coupler
Unit or the host communications master. Therefore, the interval of the timing to read inputs or to
refresh outputs for NX Unit is not always the same. (Refer to (d) in the figure below.)
• In order to read input values correctly, you must set the inputs before the total of the ON/OFF
response time and the input filter time from the timing to read inputs for each NX Unit.
• The ON/OFF response time is needed from the timing to refresh outputs until setting the output sta-
tus of external terminals on the NX Units.
NX-series Digital I/O Unit User's Manual (W521)
5 I/O Refreshing
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