214
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 (2/2)
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.
Main routine
EI
Interrupt request i
(level 2)
Processing of i
Processing of k
Interrupt
request j
(level 3)
Processing of j
Interrupt request l
(level 2)
EI
EI
EI
Interrupt request o
(level 3)
Interrupt request s
(level 1)
Interrupt request k
(level 1)
Processing of l
Processing of n
Processing of m
Processing of s
Processing of u
Processing of t
Interrupt
request m
(level 3)
Interrupt request n
(level 1)
Processing of o
Interrupt
request p
(level 2)
Interrupt
request q
(level 1)
Interrupt
request r
(level 0)
Interrupt request u
(level 2)
Note 2
Interrupt
request t
(level 2)
Note 1
Processing of p
Processing of q
Processing of r
EI
If levels 3 to 0 are acknowledged
Interrupt request j is held pending because its
priority is lower than that of i.
k that occurs after j is acknowledged because it
has the higher priority.
Interrupt requests m and n are held pending
because processing of l is performed in the
interrupt disabled status.
Pending interrupt requests are acknowledged after
processing of interrupt request l.
At this time, interrupt requests n is acknowledged
first even though m has occurred first because the
priority of n is higher than that of m.
Pending interrupt requests t and u are
acknowledged after processing of s.
Because the priorities of t and u are the same, u is
acknowledged first because it has the higher
default priority, regardless of the order in which the
interrupt requests have been generated.
Notes: 1. Lower default priority
2. Higher default priority
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