NEC mPD780973 Series Preliminary User's Manual page 238

Figure 19-11. 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 specify 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)
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CHAPTER 19 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
Start
No
××IF = 1?
Yes (Interrupt request generation)
No
××MK = 0?
Yes
××PR = 0?
No (Low priority)
Any interrupt
Yes
request among those
simultaneously generated
with ××PR = 0?
Interrupt request held pending
No
Any interrupt
Yes
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