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CHAPTER 21 INTERRUPT AND TEST FUNCTIONS
Figure 21-13. Interrupt Request Acknowledge Processing Algorithm
XXIF : Interrupt Request Flag
XXMK : Interrupt Mask Flag
XXPR : Priority Order Specification Flag
IE : 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 order
interrupt being processed, 1 = no interrupt request being received, or low priority order interrupt being
processed.)
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