Interrupt Request Acknowledge Processing Algorithm - NEC PD78081(A) User Manual

Figure 12-11. Interrupt Request Acknowledge Processing Algorithm
Interrupt request
reserve
Yes
generated
Interrupt request
reserve
No
Interrupt request
reserve
IF : Interrupt request flag
MK : Interrupt mask flag
PR : Priority specify flag
IE : Flag which controls maskable interrupt request acknowledgment (1 = enable, 0 = disable)
ISP : Flag which indicates the priority of the interrupt currently being processed. (0 = high priority
interrupt being processed, 1= interrupt request not acknowledged, or low priority interrupt
being processed.)
CHAPTER 12 INTERRUPT FUNCTION
Yes (High priority)
Do any
of the simultaneously
PR=0 interrupt
requests have a high
priority?
No
IE=1?
Yes
Vectored interrupt
servicing
Start
No
IF=1?
Yes (Interrupt Request
Generation)
No
MK=0?
Yes
PR=0?
No (Low Priority)
Any
Simultaneously
generated PR=0 interrupt
requests?
No
Any
Simultaneously
generated high-priority
interrupt requests?
No
No
IE=1?
Yes
No
ISP=1?
Yes
Vectored interrupt
servicing
Yes
Interrupt request
reserve
Yes
Interrupt request
reserve
Interrupt request
reserve
Interrupt request
reserve
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