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Interrupt Control Instructions Section 3-20
Scheduled Interrupt Processing (N=4 or 5)
A scheduled interrupt is repeated at regular intervals set with MSKS(690) and
independent of the timing of the PLC cycle. N numbers 4 and 5 correspond to
scheduled interrupt numbers 2 and 3, respectively.
Scheduled Interrupt
Processing
The main features of scheduled interrupt processing are listed below.
1,2,3... 1. The scheduled interrupts are masked (disabled) when the PLC is first
turned on.
2. Set the time to the first scheduled interrupt (after execution of MSKS(690))
with CLI(691). The time to the first scheduled interrupt is unpredictable if it
is not set with CLI(691).
3. The scheduled time interval setting and interrupt processing
• Set the scheduled time interval with MSKS(690).
• After MSKS(690) has been executed and the time to the first sched-
uled interrupt (set with CLI(691)) has passed, the task currently being
processed will be interrupted and the scheduled interrupt task will be
executed.
• When the scheduled interrupt task execution reaches an END(001) in-
struction, program execution will resume at the point where the sched-
uled interrupt occurred.
• Program execution will be interrupted and the scheduled interrupt task
will be executed again when the scheduled time interval has passed.
The scheduled interrupt task will be executed repeatedly until it is dis-
abled.
4. Disabling a Scheduled Interrupt
• A scheduled interrupt task can be disabled by setting the scheduled
time interval to 0000 with MSKS(690).
• When enabling the scheduled interrupt task again, be sure to set the
time to the first scheduled interrupt with CLI(691) before setting the
scheduled time interval again with MSKS(690).
Scheduled Interrupt
Operation
In the following example, the scheduled time interval units are set to 10 ms in
the PLC Setup.
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