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51 lines
498 B
ArmAsm
51 lines
498 B
ArmAsm
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; 2023, Rumbledethumps
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;
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; Enables the C IRQ tools
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.export initirq, doneirq
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.import callirq, _exit
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.include "rp6502.inc"
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.segment "ONCE"
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initirq:
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lda #<handler
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ldx #>handler
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sei
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sta $FFFE
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stx $FFFF
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cli
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rts
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.code
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doneirq:
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sei
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rts
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.segment "LOWCODE"
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handler:
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cld
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phx
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tsx
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pha
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inx
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inx
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lda $100,X
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and #$10
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bne break
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phy
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jsr callirq
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ply
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pla
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plx
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rti
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break:
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lda #$FF
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sta RIA_A
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jmp _exit
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