UPD784938 Datasheet, PDF (550/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 23 INTERRUPT FUNCTIONS
23.7 Maskable Interrupt Acknowledgment Operation
A maskable interrupt can be acknowledged when the interrupt request flag is set (to 1) and the mask flag for that interrupt
is cleared (to 0). When servicing is performed by macro service, the interrupt is acknowledged and serviced by macro service
immediately. In the case of vectored interruption and context switching, an interrupt is acknowledged in the interrupt enabled
state (when the IE flag is set (to 1)) if the priority of that interrupt is one for which acknowledgment is permitted.
If maskable interrupt requests are generated simultaneously, the interrupt for which the highest priority is specified by
the priority specification flag is acknowledged. If the interrupts have the same priority specified, they are acknowledged
in accordance with their default priorities.
A pending interrupt is acknowledged when a state in which it can be acknowledged is established.
The interrupt acknowledgment algorithm is shown in Figure 23-10.
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Preliminary User’s Manual U13987EJ1V0UM00