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8 Pulse Output Units
NX-series Position Interface Units User’s Manual (W524)
8-7 I/O Refreshing Method Setting
8
8-7 I/O Refreshing Method Setting
Data is exchanged between the Pulse Output Unit and the Controller through synchronous I/O refresh-
ing or task period prioritized refreshing.
You cannot use Free-Run refreshing.
You cannot use a Pulse Output Unit with a Communications Coupler Unit that does not support syn-
chronous I/O refreshing or task period prioritized refreshing.
This section describes how to set the I/O refreshing method for Pulse Output Units, the I/O refreshing
methods, and the differences in I/O refreshing methods for different Controllers.
Precautions for Correct Use
The Pulse Output Unit receives cyclic command positions or cyclic command positions and
command velocities from the Controller and uses them to control the pulse output in each
cycle. Therefore, synchronous I/O refreshing or task period prioritized refreshing is used as the
I/O refreshing method. If you incorrectly set the I/O Refresh Method to Free-Run refreshing,
this could result in unintended operation. Be sure to set the I/O Refresh Method correctly.
Example: Position-synchronous Pulse Output (for Servomotor Control)
When a position-synchronous pulse output is used, the Pulse Output Unit outputs a number of
pulses based on the command position that is received from the Controller at the speed that is
required to output all of the pulses within the synchronous refresh cycle.
If the I/O Refresh Method is set to Free-Run refreshing, the Pulse Output Unit will continuously
output pulses on an irregular cycle. This happens because the cycle when the command posi-
tion is received from the Controller and the cycle for Pulse Output Unit processing do not
match.
Refer to 8-10-3 Output Mode Selection on page 8-55 for details on a position-synchronous
pulse output.
Results (not predictable)
Controller refresh cycle
Command position refresh (output refresh)
Internal control cycle of Pulse Output Unit
Pulse output
125 μs
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