NEC uPD78P078 User Manual

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CHAPTER 22 INTERRUPT FUNCTIONS

Figure 22-13. Interrupt Request Acknowledge Processing Algorithm

xxIF

: Interrupt request flag

xxMK : Interrupt mask flag

xxPR : Priority specify flag

: 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

Vectored interrupt
servicing

Any high-

priority interrupt among

simultaneously generated

xx PR = 0 interrupt

requests?

IE = 1?

Yes (High priority)

Yes

Yes (Interrupt Request
Generation)

Yes

No (Low Priority)

Yes

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