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CHAPTER 21 INTERRUPT AND TEST FUNCTIONS

Figure 21-13. Interrupt Request Acknowledge Processing AlgorithmXXIF : Interrupt Request FlagXXMK: Interrupt Mask FlagXXPR : Priority Order Specification FlagIE : Flag which controls reception of maskable interrupt requests (1 = permitted, 0 = prohibited)ISP : Flag which shows the priority order of the interrupt currently being processed (0 = high priority orderinterrupt being processed, 1 = no interrupt request being received, or low priority order interrupt beingprocessed.)

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
Does one of
the simultaneously generated
XXPR=0 interrupt request have a
high priority?

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