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CHAPTER 21 INTERRUPT AND TEST FUNCTIONS
Figure 21-13. Interrupt Request Acknowledge Processing Algorithm
××IF : Interrupt request flag
××MK : Interrupt mask flag
××PR : Priority specify flag
IE : Flag to control acknowledgment of maskable interrupt request (1 = enable, 0 = disable)
ISP : Flag to indicate the priority of interrupt currently being serviced (0 = servicing interrupt of high priority,
1 = not acknowledging interrupt request or servicing interrupt of low priority)
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
Any high-
priority interrupt request
among simultaneously generated
××PR=0 interrupt
requests?
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