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CHAPTER 3 CPU
G
Example of multiple interrupts
As an example of multiple interrupt processing, assuming that a timer interrupt is preferred to an A/D
converter interrupt, set the interrupt level of the A/D converter to 2 and the interrupt level of the timer to 1.
Figure 3.5-8 shows the processing of the timer interrupt generated during processing of the A/D converter
interrupt.
Main program
ILM="111
Setting interrupt
A/D interrupt
generate
Main processing
restart
• When processing of the A/D converter interrupt is started, the interrupt level mask register (ILM) is set
automatically to the value (2 in example) of the interrupt level (ICR: IL2 to IL0) of the A/D converter.
When an interrupt request with an interrupt level of 1 or 0 is generated under this condition, processing
the generated interrupt is preferred.
• When the interrupt return instruction (RETI) is executed after the completion of interrupt processing, the
values of the dedicated registers (A, DPR, ADB, DTB, PCB, PC, PS) saved in the system stack are
returned to each register and the interrupt level mask register (ILM)
76
Figure 3.5-8 Example of multiple interrupts
"
B
A/D interrupt processing ILM="010
Interrupt level 2
IL="010
"
B
1
3
Timer interrupt generate
2
Suspend
Restart
8
6
A/D interrupt processing
A/D interrupt return
7
"
B
Timer interrupt processing (ILM="001
Interrupt level 1
IL="001
"
B
4
Timer interrupt
processing
Timer interrupt
5
return
")
B
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