CHAPTER 15 INTERRUPT FUNCTIONS
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15.4 Interrupt Processing Operation
15.4.1 Non-maskable interrupt request acknowledgement operation
The non-maskable interrupt request is unconditionally acknowledged even when interrupts are disabled. It is not
subject to interrupt priority control and takes precedence over all other interrupts.
When the non-maskable interrupt request is acknowledged, PSW and PC are saved to the stack in that order, the
IE flag is reset to 0, the contents of the vector table are loaded to the PC, and then program execution branches.
Figure 15-6 shows the flowchart from non-maskable interrupt request generation to acknowledgement. Figure
15-7 shows the timing of non-maskable interrupt request acknowledgement. Figure 15-8 shows the acknowledgement
operation if multiple non-maskable interrupts are generated.
Caution During a non-maskable interrupt service program execution, do not input another non-maskable
interrupt request; if it is input, the service program will be interrupted and the new interrupt
request will be acknowledged.
Summary of Contents for mPD789101
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