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cc65/libsrc/cbm610/clrscr.s

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;
; Ullrich von Bassewitz, 22.09.1998
;
; void clrscr (void);
;
.export _clrscr
.import plot
.include "cbm610.inc"
.proc _clrscr
lda #0
sta CURS_X
sta CURS_Y
jsr plot ; Set cursor to top left corner
lda IndReg
pha
lda #$0F
sta IndReg ; Switch to the system bank
ldx #8
ldy #$00
lda #$20 ; Screencode for blank
L1: sta (CharPtr),y
iny
bne L1
inc CharPtr+1
dex
bne L1
pla
sta IndReg ; Restore old indirect segment
jmp plot ; Set screen pointer again
.endproc