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cc65/libsrc/atari/irq.s

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;
; IRQ handling (ATARI version)
;
.export initirq, doneirq
.import callirq
.include "atari.inc"
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.ifdef __ATARIXL__
.import __CHARGEN_START__
.include "romswitch.inc"
.endif
; ------------------------------------------------------------------------
.segment "INIT"
initirq:
lda VVBLKD
ldx VVBLKD+1
sta IRQInd+1
stx IRQInd+2
lda #7
ldy #<IRQStub
ldx #>IRQStub
jsr SETVBV
rts
; ------------------------------------------------------------------------
.code
doneirq:
lda #7
ldy IRQInd+1
ldx IRQInd+2
jsr SETVBV
rts
; ------------------------------------------------------------------------
.segment "LOWCODE"
IRQStub:
cld ; Just to be sure
.ifdef __ATARIXL__
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.ifdef CHARGEN_RELOC
lda CHBAS
pha
.endif
lda PORTB
pha
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and #$FE
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sta PORTB ; disable ROM
set_chbase >__CHARGEN_START__
.endif
jsr callirq ; Call the functions
.ifdef __ATARIXL__
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pla
sta PORTB ; restore old ROM setting
.ifdef CHARGEN_RELOC
pla
sta CHBAS
sta CHBASE
.endif
.endif
jmp IRQInd ; Jump to the saved IRQ vector
; ------------------------------------------------------------------------
.data
IRQInd: jmp $0000