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32 lines
777 B
ArmAsm
32 lines
777 B
ArmAsm
;
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; void clrscr (void);
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;
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.export _clrscr
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.import plot
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.importzp CURS_X, CURS_Y
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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:
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lda #$20 ;' '
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ldy #BANKS
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ldx #$00
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staloc:
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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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lda #$00 ; cursor in upper left corner
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sta CURS_X
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sta CURS_Y
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jmp plot ; Set the cursor position
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