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Chapter 8
Interrupt/Exception Processing Function
Preliminary User’s Manual U15839EE1V0UM00
Figure 8-8:
Example of Processing in Which Another Interrupt Request Is Issued
While an Interrupt Is Being Processed (1/2)
Caution:
The values of the EIPC and EIPSW registers must be saved before executing multiple
interrupts. When returning from multiple interrupt servicing, restore the values of
EIPC and EIPSW after executing the DI instruction.
Remarks: 1. <a> to <u> in the figure are the temporary names of interrupt requests shown for the
sake of explanation.
2. The default priority in the figure indicates the relative priority between two interrupt
requests.
Main routine
EI
EI
Interrupt request a
(level 3)
Processing of a
Processing of b
Processing of c
Interrupt request c
(level 3)
Processing of d
Processing of e
EI
Interrupt request e
(level 2)
Processing of f
EI
Processing of g
Interrupt request g
(level 1)
Interrupt request h
(level 1)
Processing of h
Interrupt request b is acknowledged because the
priority of b is higher than that of a and interrupts are
enabled.
Although the priority of interrupt request d is higher
than that of c, d is held pending because interrupts
are disabled.
Interrupt request f is held pending even if interrupts are
enabled because its priority is lower than that of e.
Interrupt request h is held pending even if interrupts are
enabled because its priority is the same as that of g.
Interrupt
request b
(level 2)
Interrupt request d
(level 2)
Interrupt request f
(level 3)
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