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CHAPTER 12 INTERRUPT FUNCTION
Figure 12-11. Interrupt Request Acknowledge Processing Algorithm
Start
× × IF=1?
× × MK=0?
× × PR=0?
Any
Simultaneously
generated ××PR=0 interrupt
requests?
Any
Simultaneously
generated high-priority
interrupt requests?
IE=1?
ISP=1?
Vectored interrupt
servicing
Interrupt request
reserve
Interrupt request
reserve
Interrupt request
reserve
Interrupt request
reserve
Interrupt request
reserve
Interrupt request
reserve
Interrupt request
reserve
Vectored interrupt
servicing
IE=1?
Yes (High priority)
Yes
No
Yes
No
No
No
Yes (Interrupt Request
Generation)
No
Yes
No (Low Priority)
Yes
Yes
No
Yes
Yes
No
No
Do any
of the simultaneously
generated ××PR=0 interrupt
requests have a high
priority?
××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.)