Mitsubishi Electric melsec q00ujcpu User Manual page 48

(3) Operation when an interrupt factor occurs
There are restrictions on interrupt programs depending on the interrupt factor occurrence timing.
(a) When an interrupt factor occurs before the interrupt program execution status is enabled
The CPU module stores the interrupt factor occurred.
As soon as the interrupt program execution status is enabled, the CPU module executes the
interrupt program corresponding to the stored interrupt factor.
Main routine
program
Interrupt
program
Figure 2.11 When an interrupt factor occurs before interrupts are enabled
When the same interrupt factor occurs more than one time before the interrupt program execution
status is enabled, the interrupt factors of I0 to I15, I28 to I31, I45, I50 to I255, and fixed scan
execution type programs are stored only once.
Note that all interrupt factors occurred are discarded if they are masked by the IMASK instruction.
Remark
For details of the IMASK instruction, refer to the following.
QCPU Programming Manual (Common Instructions)
(b) When an interrupt factor occurs in the STOP or PAUSE status
The CPU module executes the interrupt program corresponding to the interrupt factor as soon as
the interrupt program execution status is enabled after the CPU module status is changed to RUN.
Main routine
program
Interrupt
program
Figure 2.12 When an interrupt factor occurs in the STOP or PAUSE status
Interrupt factor
occurrence
Not executed because
the interrupt program
execution status is
disabled (DI).
STOP/PAUSE
Interrupt factor
occurrence
Not executed because
the CPU module is in
the STOP status.
CHAPTER2 SEQUENCE PROGRAMS
Interrupt
enabled (EI)
Execution
Executed as soon as
the interrupt program
execution status
changes to enabled.
RUN Interrupt
enabled (EI)
Execution
Executed as soon as the interrupt
program execution status changes
to enabled after the CPU module
status is changed from
STOP/PAUSE to RUN.
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