NEC mPD178054 Series User Manual page 170

Figure 12-10. Interrupt Request Acknowledgement Processing Algorithm
Interrupt request
pending
Yes
Interrupt request
pending
No
Interrupt request
pending
××IF:
Interrupt request flag
××MK: Interrupt mask flag
××PR: Priority specification flag
IE: Flag controlling acknowledging maskable interrupt request (1 = enable, 0 = disable)
ISP: Flag indicating priority of interrupt currently being serviced (0 = interrupt with high priority serviced,
1 = interrupt request is not acknowledged, or interrupt with low priority serviced)
170
CHAPTER 12 INTERRUPT FUNCTIONS
Yes (High priority)
Any high-
priority interrupt request among
simultaneously generated
××
PR = 0 interrupts?
No
IE = 1?
Yes
Vectored interrupt
servicing
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No
××IF = 1?
Yes (interrupt request
generation)
No
××MK = 0?
Yes
××PR = 0?
No (Low priority)
Any
simultaneously
Yes
××
generated PR = 0
interrupt requests?
No
Any
simultaneously
Yes
generated high-priority
interrupt requests ?
No
No
IE = 1?
Yes
No
ISP = 1?
Yes
Vectored interrupt
servicing
Interrupt request
pending
Interrupt request
pending
Interrupt request
pending
Interrupt request
pending