NEC mPD780024AS Series Preliminary User's Manual page 260

Figure 15-11. Interrupt Request Acknowledge 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 acknowledge 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)
260
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
Preliminary User's Manual U16035EJ1V0UM
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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