36 lines
777 B
ArmAsm
36 lines
777 B
ArmAsm
;
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; Christian Groessler, May-2014
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;
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; void clrscr (void);
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;
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.export _clrscr
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.include "atari5200.inc"
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.importzp ptr1
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.importzp screen_width, screen_height
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SCRSIZE = screen_width * screen_height
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_clrscr:lda SAVMSC ; screen memory
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sta ptr1
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lda SAVMSC+1
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clc
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adc #>(SCRSIZE-1)
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sta ptr1+1
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lda #0 ; screen code of space char
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ldy #<(SCRSIZE-1)
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ldx #>(SCRSIZE-1)
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_clr1: sta (ptr1),y
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dey
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bne _clr1
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sta (ptr1),y
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dex
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bmi done
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dec ptr1+1
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dey
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jmp _clr1
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done: sta COLCRS_5200
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sta ROWCRS_5200
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rts
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