5 I/O Refreshing
5 - 28
NX-series Digital I/O Unit User’s Manual (W521)
z CPU Unit Operation
The following describes the operation of output refreshing with specified time stamp between the
NX-series NX1P2 CPU Unit and the NX Units.
• You can specify the specified time and the output set value for each output bit. You can also set
the same specified time for multiple output bits.
• The NX Bus Function Module of the CPU Unit sets the output set values and the specified times
to the NX Units and acquires the output status at I/O refreshing. (Refer to (a) in the figure below.)
• The output status is used when you determine that the output was refreshed normally at the spec-
ified time. Refer to 5-2-10 An Example of Turning ON Outputs at Specific Times After the Sensor
Inputs Change on page 5-33 for an example of determining that the output was refreshed.
• The NX Units turn ON the output status when the specified times are set.
• The NX Units refresh outputs and turn OFF the output status at the specified times. The values of
outputs that the NX Units refresh are the output set values at the specified times. (Refer to (b) in
the figure below.)
• The ON/OFF response time is needed from the specified time until setting the output status of
external terminals on the NX Units.
• If the next specified time is set before the current specified time is reached, the NX Units overwrite
the current specified time to the next specified time. The current specified time is ignored.
• If the value of the specified time is 0, the output is refreshed immediately. At this time, the Output
Units refresh outputs according to the output set values.
• When the specified time is set to the NX Units, if the specified time is a previous DC time, a Previ-
ous Time Specified event (event code: 7001000 hex) occurs.
• To make the specified time as a future DC time when it is set to the NX Units, set the specified
time to satisfy both the following conditions.
a) A future DC time at least twice the task period from the previous value of the Time Stamp of Syn-
chronous Output (Refer to (c) in the figure below.)
b) A future DC time at least three times the task period from the input changed time read from the
Input Units that support input refreshing with input changed time (Refer to (d) in the figure below.)
• The Time Stamp of Synchronous Output is one of I/O data in the NX Bus Function Module of the
CPU Unit, and contains the DC time of synchronous outputs from the NX Unit. The I/O port name
for this I/O data is " Time Stamp of Synchronous Output"
*1
. This I/O data is allocated per NX
Unit to a CPU Unit.
*1. "" is a device name.
Description of Operation
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