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159 lines
2.2 KiB
NASM
159 lines
2.2 KiB
NASM
// Illustrates a problem where local variables inside an IRQ are assigned the same zeropage as a variable outside the IRQ
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.pc = $801 "Basic"
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:BasicUpstart(main)
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.pc = $80d "Program"
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.label KERNEL_IRQ = $314
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.label RASTER = $d012
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.label VIC_CONTROL = $d011
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.label IRQ_STATUS = $d019
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.label IRQ_ENABLE = $d01a
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.const IRQ_RASTER = 1
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.label BGCOL = $d020
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.label FGCOL = $d021
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.label CIA1_INTERRUPT = $dc0d
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.const CIA_INTERRUPT_CLEAR = $7f
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main: {
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.label k = 4
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.label j = 3
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.label i = 2
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sei
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// Disable CIA 1 Timer IRQ
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lda #CIA_INTERRUPT_CLEAR
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sta CIA1_INTERRUPT
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// Set raster line to $0fd
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lda #$7f
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and VIC_CONTROL
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sta VIC_CONTROL
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lda #$fd
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sta RASTER
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// Enable Raster Interrupt
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lda #IRQ_RASTER
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sta IRQ_ENABLE
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// Set the IRQ routine
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lda #<irq
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sta KERNEL_IRQ
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lda #>irq
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sta KERNEL_IRQ+1
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cli
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b1:
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lda #0
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sta.z i
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__b1:
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lda #0
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sta.z j
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__b2:
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lda #0
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sta.z k
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__b3:
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lda.z i
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clc
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adc.z j
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clc
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adc.z k
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sta FGCOL
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jsr sub_main
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inc.z k
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lda #$b
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cmp.z k
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bne __b3
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inc.z j
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cmp.z j
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bne __b2
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inc.z i
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cmp.z i
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bne __b1
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jmp b1
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}
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sub_main: {
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.label i = 5
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lda #0
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sta.z i
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__b1:
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ldx #0
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__b2:
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ldy #0
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__b3:
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txa
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clc
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adc.z i
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sty.z $ff
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clc
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adc.z $ff
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sta BGCOL
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iny
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cpy #$b
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bne __b3
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inx
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cpx #$b
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bne __b2
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inc.z i
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lda #$b
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cmp.z i
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bne __b1
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rts
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}
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irq: {
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.label k = 8
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.label j = 7
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.label i = 6
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inc BGCOL
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lda #0
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sta.z i
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__b1:
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lda #0
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sta.z j
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__b2:
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lda #0
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sta.z k
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__b3:
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lda.z i
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clc
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adc.z j
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clc
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adc.z k
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sta FGCOL
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jsr sub_irq
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inc.z k
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lda #$b
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cmp.z k
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bne __b3
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inc.z j
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cmp.z j
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bne __b2
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inc.z i
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cmp.z i
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bne __b1
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lda #IRQ_RASTER
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sta IRQ_STATUS
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dec BGCOL
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jmp $ea81
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}
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sub_irq: {
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.label i = 9
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lda #0
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sta.z i
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__b1:
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ldx #0
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__b2:
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ldy #0
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__b3:
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txa
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clc
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adc.z i
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sty.z $ff
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clc
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adc.z $ff
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sta BGCOL
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iny
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cpy #$b
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bne __b3
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inx
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cpx #$b
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bne __b2
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inc.z i
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lda #$b
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cmp.z i
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bne __b1
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rts
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}
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