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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 flagIE : 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 priorityinterrupt being processed, 1= interrupt request not acknowledged, or low priority interruptbeing processed.)