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24 lines
491 B
ArmAsm
24 lines
491 B
ArmAsm
;
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; void clrscr (void);
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;
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.export _clrscr
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.include "c1p.inc"
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; Adapted from the Challenger Character Graphics
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; Reference Manual, "2.3.3 MACHINE LANGUAGE SCREEN CLEAR"
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; This is self-modifying code!
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BANKS = VIDEORAMSIZE / $100
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_clrscr: LDA #$20 ;' '
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LDY #BANKS
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LDX #$00
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STALOC: STA SCRNBASE,X
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INX
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BNE STALOC
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INC STALOC+2
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DEY
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BNE STALOC
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LDA #>(SCRNBASE) ; load high byte
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STA STALOC+2 ; restore base address
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RTS
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