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;
; IRQ handling (ATARI version)
;
.export initirq, doneirq
.import callirq
.include "atari.inc"
.ifdef __ATARIXL__
.import __CHARGEN_START__
.include "romswitch.inc"
.endif
; ------------------------------------------------------------------------
.segment "ONCE"
initirq:
lda #$4C ; JMP opcode
sta IRQInd
lda VVBLKD
ldx VVBLKD+1
sta IRQInd+1
stx IRQInd+2
lda #7
ldy #<IRQStub
ldx #>IRQStub
jmp SETVBV
; ------------------------------------------------------------------------
.code
doneirq:
lda #7
ldy IRQInd+1
ldx IRQInd+2
jmp SETVBV
; ------------------------------------------------------------------------
.segment "LOWCODE"
IRQStub:
cld ; Just to be sure
.ifdef __ATARIXL__
.ifdef CHARGEN_RELOC
lda CHBAS
pha
.endif
.endif
lda PORTB
pha
.ifdef __ATARIXL__
and #$FE ; disable ROM
.endif
ora #$10 ; map main memory into $4000..$7FFF area
sta PORTB
.ifdef __ATARIXL__
set_chbase >__CHARGEN_START__
.endif
jsr callirq ; Call the functions
pla
sta PORTB ; restore old memory settings
.ifdef __ATARIXL__
.ifdef CHARGEN_RELOC
pla
sta CHBAS
sta CHBASE
.endif
.endif
jmp IRQInd ; Jump to the saved IRQ vector
; ------------------------------------------------------------------------
.segment "LOWBSS"
IRQInd: .res 3
.end
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