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49 lines
1001 B
ArmAsm
49 lines
1001 B
ArmAsm
;
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; 2003-04-13, Ullrich von Bassewitz
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; 2013-07-16, Greg King
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;
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.export _clrscr
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.importzp ptr2
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.include "atmos.inc"
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; ------------------------------------------------------------------------
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; void clrscr (void);
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.proc _clrscr
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; Set the cursor to top left cursor position
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ldy #$00
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sty CURS_X
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sty CURS_Y
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; Set ptr2 to the screen position (left upper border)
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lda #<SCREEN
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sta ptr2
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lda #>SCREEN
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sta ptr2+1
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; Clear full pages. Y is still zero
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ldx #>(SCREEN_YSIZE * SCREEN_XSIZE)
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lda #' '
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@L1: sta (ptr2),y
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iny ; Bump low byte of address
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bne @L1
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inc ptr2+1 ; Bump high byte of address
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dex
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bne @L1
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; Clear the remaining page
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@L2: sta (ptr2),y
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iny
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cpy #<(SCREEN_YSIZE * SCREEN_XSIZE)
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bne @L2
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rts
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.endproc
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