UPD17062 datasheet(133/298 Pages) RENESAS

133 / 298 page

131

µPD17062

11.9.4

Saving the Contents of System and Control Registers

The contents of system and control registers must be saved before using the multiple interrupt function.

The contents of these registers change during interrupt processing.

An area must be obtained for these contents for each interrupt source.

An interrupt being accepted and interrupts with lower priorities must be inhibited, and interrupts with

higher priorities must be permitted.

Because an interrupt with a high priority is an emergency interrupt, it should have first priority. Therefore,

the contents of system and control registers should be saved after permitting an interrupt with a high priority.

The following example describes processing of the interrupt processing routine to enable an interrupt with

a high priority and to save the contents of system and control registers:

Example

Example of permitting an interrupt and saving register contents at multiple interrupts

Use the INTNC pin, VSYNC pin, and timer interrupts with the following software priorities:

VSYNC pin > timer > INTNC pin

A timer interrupt is assumed to be accepted in the first level.

The figure below shows an example program and flowchart for this processing.

Flowchart

Program example

(

)

RETI

MOV

POKE

BANK1

POKE

PEEK

POKE

MOV

POKE

PEEK

POKE

PEEK

POKE

PEEK

POKE

PEEK

WR,

INTPM,

#0111B

INTPM

#0100B

WR,

M3,

WR,

INTPM,

WR,

INTPM,

WR,

RPL

M1,

WR,

M2,

WR,

INTPM,

VSYNC, INTNC, and timer

interrupt permission

;

(built-in macro)

;

Bank specification

Window register saving

Interrupt permission flag

saving

Permission of interrupt

with high priority

System register saving

Interrupt processing

System register restoration

Interrupt permission

flag restoration

Window register restoration

Permit timer, INTNC pin, and VSYNC pin interrupts

using the interrupt permission register.

The contents of the bank register, index enable flag,

and program counter are automatically saved.

Restore the contents of the interrupt

permission register.

Restores the contents of the window register.

Restore the contents of system

and control registers other than window

and interrupt permission registers.

Save the contents of system and

control registers other than window

and interrupt permission registers.

Saves the window register.

Save the interrupt permission

Permit a VSYNC pin interrupt using

the interrupt permission register.

Specifies that the data is saved in BANK1.

Timer interrupt

Main routine

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