Mitsubishi Electric MELSEC iQ-R Series User Manual page 122

• For I28 to I31, I48, and I49
The interrupt factor that has occurred is memorized. After the running interrupt program finishes, the interrupt program
corresponding to the factor will be executed. If the same interrupt factor occurs multiple times, it will be memorized once but
operation at the second and later occurrences depends on setting of the fixed scan execution mode ( Page 105 Fixed
scan execution mode). When "Execution Count Takes Priority" is enabled, the interrupt program corresponding to the
memorized interrupt factor will be executed after the running interrupt program finishes. When "Precede Fixed Scan" is
enabled, the second and later occurrences will not be memorized.
When interrupts with lower priority level than the one being executed occur
Main routine program
High
I49 interrupt program
I28 interrupt program
Low
(1) The second and following interrupt factors that occur while interrupts are being executed operate according to the setting of the fixed scan execution mode.
(2) The program is not executed for the second time.
(3) After the interrupt in execution is completed, interrupts are executed in order from I29 because it has a higher priority.
(4) The second interrupt is executed.
When interrupts with the same priority level as the one being executed occur
Main routine program
High
I31 interrupt program
I29 interrupt program
I28 interrupt program
Low
Priority level of interrupt:
I31 = I29 = I28
(1) The second and following interrupt factors that occur while interrupts are being executed operate according to the setting of the fixed scan execution mode.
(2) The program is not executed for the second time.
(3) After the interrupt in execution is completed, interrupts are executed in order from I29 because it has a higher priority.
(4) The second interrupt is executed.
8 RUNNING A PROGRAM
120
8.7 Interrupt Program
I49
I28
When "Execution Count Takes
Priority" is set
I31
I28 I29
I28 I29
When "Execution Count Takes
Priority" is set
From A From B
(3)
I28
When "Fixed Scan Takes
Priority" is set
(3)
(1)
When "Fixed Scan Takes
Priority" is set
×
B
(4)
(4)
(1)
(2)
(4)
(2)
A
t
t