NEC 78K0 User Manual page 324

Figure 15-7. Interrupt Request Acknowledgment Processing Algorithm
Interrupt request held pending
Yes
Interrupt request held pending
Interrupt request held pending
××IF:
Interrupt request flag
××MK: Interrupt mask flag
××PR: Priority specification flag
IE: Flag that controls acknowledgment of maskable interrupt request (1 = Enable, 0 = Disable)
ISP: Flag that indicates the priority level of the interrupt currently being serviced (0 = High-priority interrupt
servicing, 1 = No interrupt request acknowledged, or low-priority interrupt servicing)
324
CHAPTER 15 INTERRUPT FUNCTIONS
Yes (High priority)
Any high-priority
interrupt request among those
simultaneously generated
with ××PR = 0?
No
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 high-priority
interrupt request among
those simultaneously generated
with ××PR = 0?
Interrupt request held pending
No
Any high-priority
Yes
interrupt request among
those simultaneously
generated?
Interrupt request held pending
No
No
IE = 1?
Yes
Interrupt request held pending
No
ISP = 1?
Yes
Interrupt request held pending
Vectored interrupt servicing
Yes