UPD784938 Datasheet, PDF (556/733 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 (2/3)
Interrupt request i
(level 1)
Main routine
EI
Macro service
request j
(level 2)
i servicing
j macro service
The macro service request is
serviced irrespective of interrupt
enabling/disabling and priority.
Interrupt request k
(level 2)
k servicing
Interrupt ^EI
request l
(level 3)
Interrupt
request m
(level 1)
m servicing
l servicing
The interrupt request is held
peding since it has a lower
priority than interrupt request k.
Interrupt request m generated
after interrupt request l has a
higher priority, and is therefore
acknowledged first.
Interrupt request n
(level 2)
n servicing
Interrupt
request o
(level 3)
Interrupt
request p
(level 1)
p servicing
o servicing
Since servicing of interrupt
request n performed in the
interrupt disabled state,
interrupt requests o and p
are held pending.
After interrupt request n
servicing, the pending interrupt
requests are acknowledged.
Although interrupt request o
was generated first, interrupt
request p has a higher priority
and is therefore acknowledged
first.
556
Preliminary User’s Manual U13987EJ1V0UM00