NEC uPD78P078 - Manual (Page 517)

517
CHAPTER 22 INTERRUPT FUNCTIONS
Figure 22-13. Interrupt Request Acknowledge Processing Algorithm
xxIF : Interrupt request flag
xxMK : Interrupt mask flag
xxPR : Priority specify flag
IE : Flag to control maskable interrupt request acknowledge
ISP : Flag to indicate the priority of interrupt being serviced (0 = an interrupt with higher priority
is being serviced, 1 = interrupt request is not acknowledged or an interrupt with lower
priority is being serviced)
Start
xxIF = 1?
xxMK = 0?
xxPR = 0?
Any
simultaneously generated
high-priority interrupt
requests?
Any
simultaneously generated
xxPR = 0 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 among
simultaneously generated
xx 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