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https://gitlab.com/camelot/kickc.git
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87 lines
1.9 KiB
NASM
87 lines
1.9 KiB
NASM
// Test interrupt routine using a variable between calls (irq_idx)
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.pc = $801 "Basic"
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:BasicUpstart(bbegin)
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.pc = $80d "Program"
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.label RASTER = $d012
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.label VIC_CONTROL = $d011
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// VIC II IRQ Status Register
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.label IRQ_STATUS = $d019
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// VIC II IRQ Enable Register
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.label IRQ_ENABLE = $d01a
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// Bits for the IRQ Status/Enable Registers
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.const IRQ_RASTER = 1
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// CIA#1 Interrupt Status & Control Register
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.label CIA1_INTERRUPT = $dc0d
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// Value that disables all CIA interrupts when stored to the CIA Interrupt registers
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.const CIA_INTERRUPT_CLEAR = $7f
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// The vector used when the KERNAL serves IRQ interrupts
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.label KERNEL_IRQ = $314
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.label SCREEN = $400
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.label VIC_BASE = $d000
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.const VIC_SIZE = $30
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.const IRQ_CHANGE_NEXT = $7f
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.label irq_idx = 2
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bbegin:
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lda #0
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sta irq_idx
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jsr main
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main: {
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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 $60
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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 #$60
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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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// Acknowledge any IRQ
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sta IRQ_STATUS
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// Setup the table driven IRQ routine
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lda #<table_driven_irq
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sta KERNEL_IRQ
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lda #>table_driven_irq
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sta KERNEL_IRQ+1
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cli
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rts
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}
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table_driven_irq: {
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b1:
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ldy irq_idx
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lda IRQ_CHANGE_IDX,y
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ldx IRQ_CHANGE_VAL,y
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inc irq_idx
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cmp #VIC_SIZE
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bcc b2
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cmp #VIC_SIZE+8
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bcc b3
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lda #IRQ_RASTER
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sta IRQ_STATUS
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stx RASTER
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ldy RASTER
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sty $ff
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cpx $ff
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bcc !_ea81+
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jmp $ea81
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!_ea81:
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lda #0
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sta irq_idx
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jmp $ea81
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b3:
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tay
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txa
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sta SCREEN+-VIC_SIZE+$3f8,y
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jmp b1
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b2:
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tay
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txa
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sta VIC_BASE,y
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jmp b1
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}
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IRQ_CHANGE_VAL: .byte $b, $b, $63, 0, 0, $80, 7, 7, $83, 0, 0, $60
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IRQ_CHANGE_IDX: .byte $20, $21, IRQ_CHANGE_NEXT, $20, $21, IRQ_CHANGE_NEXT, $20, $21, IRQ_CHANGE_NEXT, $20, $21, IRQ_CHANGE_NEXT
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