Omron CJ1G-CPU series, Programming Manual

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Interrupt Tasks Section 4-3
Interrupt during Interrupt Task Execution
If an interrupt occurs while another interrupt task is being executed, the task
for the interrupt will not be executed until the original interrupt finishes execut-
ing.
Note If you do not want a specific I/O interrupt task number to be saved and exe-
cuted for a CS-series CPU Unit when it occurs while another interrupt task is
being executed, execute the CLI (CLEAR INTERRUPT) instruction from the
other interrupt task to CLEAR the interrupt number saved internally. Sched-
uled interrupts and external interrupts cannot be cancelled.
Multiple Interrupts Occurring Simultaneously
Interrupt tasks other than power OFF interrupt tasks will be executed in the
following order of priority whenever multiple interrupts occur simultaneously.
I/O interrupt tasks (CS Series only) > external interrupt tasks (CS Series only)
> scheduled interrupt tasks
Each of the various types of interrupt task will be executed in order starting
from the lowest number if more than one occurs.
Note Only one interrupt will be recorded in memory for each interrupt task and an
interrupt will not be recorded for an interrupt that is already being executed.
Because of the low order of priority of scheduled interrupts and because that
only one interrupt is recorded at a time, it is possible for a scheduled interrupt
to be skipped.
4-3-3 Interrupt Task Flags and Words
Maximum Interrupt Task Processing Time (A440)
The maximum processing time for an interrupt task is stored in binary data in
0.1-ms units and is cleared at the start of operation.
Cyclic task
Interrupt task A
Interrupt during
execution
Interrupt task B
Interrupt task A will continue
until it finishes executing.
Cyclic task
Interrupt task 101 will be ignored while
another interrupt task is being executed.
Interrupt task A
Interrupt
during
execution
I/O interrupt task
Interrupt task 101 will
not be executed.