Selecting Nx Units; Free-Run Refreshing - Omron NX-ID User Manual

5 I/O Refreshing
*1. Two types of time stamp refreshing are available: one is input refreshing with input changed time and the other
is output refreshing with specified time stamp.
*2. The EtherCAT Slave Terminal operates in DC Mode.
*3. The EtherCAT Slave Terminal operates in Free-Run Mode.
*4. Refer to P. 5-26 and P. 5-32 for information on the operation when the DC is set to Disabled (FreeRun).
5-2-3

Selecting NX Units

The I/O refreshing methods that you can use depend on the model of the NX Unit. After you decide on
which I/O refreshing method to use, select the NX Units.
5-2-4

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
CPU Unit Operation
The following describes the operation of Free-Run refreshing between the NX-series NX1P2 CPU
Unit and the NX Units.
• The CPU Unit performs I/O refreshing for NX Units. (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 CPU 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, timing to read
inputs or to refresh outputs for each NX Unit 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 CPU Unit. 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
status of external terminals on the NX Units.
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NX-series Digital I/O Unit User's Manual (W521)