Priorities Of Maskable Interrupts - NEC V850/SA1 mPD703015 Preliminary User's Manual

5.3.3 Priorities of maskable interrupts

The V850/SA1 provides multiple interrupt service which accepts an interrupt while servicing another interrupt.
Multiple interrupts can be controlled by priority levels.
There are two types of priority level control: control based on the default priority levels, and control based on the
programmable priority levels which are specified by interrupt priority level specification bit (xxPRn). When two or
more interrupts having the same priority level specified by xxPRn are generated at the same time, interrupts are
serviced in order depending on the priority level allocated to each interrupt request types (default priority level) be-
forehand. For more information, refer to Table 5-1. The programmable priority control customizes interrupt requests
into eight levels by setting the priority level specification flag.
Note that when an interrupt request is acknowledged, the ID flag of PSW is automatically set to ''1''. Therefore,
when multiple interrupts are to be used, clear the ID flag to ''0'' beforehand (for example, by placing the EI instruction
into the interrupt service program) to set the interrupt enable mode.
CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
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