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R01UH0336EJ0102 Rev.1.02
Page 186 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 4 Interrupt Functions
Figure 4-6
Example of Processing in which Another Interrupt Request Signal is
Issued while an Interrupt is being Serviced (1/2)
Caution
To perform multiple interrupt servicing, the values of the EIPC and EIPSW registers must be
saved before executing the EI instruction. When returning from multiple interrupt servicing,
restore the values of EIPC and EIPSW after executing the DI instruction.
Note 1.
The letters a to h in the figure are simply labels for convenient reference to the
interrupt requests in the explanation.
Note 2.
The default priority in the figure indicates the relative priority between two interrupt
request signals.
Main routine
EI
EI
Interrupt request a
(level 3)
Servicing of a
Servicing of b
Servicing of c
Interrupt request c
(level 3)
Servicing of d
Servicing of e
EI
Interrupt request e
(level 2)
Servicing of f
EI
Servicing of g
Interrupt request g
(level 1)
Interrupt
request h
(level 1)
Servicing 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)