UPD784938 Datasheet, PDF (555/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 23 INTERRUPT FUNCTIONS
Figure 23-13. Examples of Servicing when Another Interrupt Request is Generated During Interrupt Service (1/3)
Main routine
Interrupt request a
(level 3)
a servicing
EI
EI
Interrupt
request b
(level 2)
b servicing
Since interrupt request b has a higher
priority than interrupt request a, and
interrupts are enabled, interrupt
request b is acknowledged.
c servicing
Interrupt request c
(level 3)
Interrupt
request d
(level 2)
d servicing
The priority of interrupt request d is
higher than that of interrupt request c,
but since interrupts are disabled,
interrupt request d is held pending.
Interrupt request e
(level 2)
e servicing
EI
Interrupt
request f
(level 3)
f servicing
Although interrupts are enabled,
interrupt request f is held pending
since it has a lower priority than
interrupt request e.
Interrupt request g
(level 1)
Interrupt
request h
(level 1)
g servicing
EI
h servicing
Although interrupts are enabled,
interrupt request h is held pending
since it has the same priority as
interrupt request g.
Preliminary User’s Manual U13987EJ1V0UM00
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