1;* 2;* clrscr 3;* 4;* NB: All screen functions assume Graphics Mode 1 in a default configuration. 5;* Therefore, this is hard coded to use $1000-$12FF as screen VRAM. 6 7 .export _clrscr 8 .include "creativision.inc" 9 10_clrscr: 11 12 sei ; Disable interrupts. Default INT handler reads VDP_STATUS 13 ; and would lose any setup done here. 14 15 lda #$00 ; VRAM offset low 16 sta VDP_CONTROL_W 17 18 lda #$50 ; VRAM offset high ($10 OR $40) 19 sta VDP_CONTROL_W 20 21 lda #$40 ; Space char from ROM setup 22 23 ldx #0 24 ldy #3 25 26L1: sta VDP_DATA_W 27 inx 28 bne L1 29 dey 30 bne L1 31 32 cli ; Let interrupts go again 33 34 lda #0 35 sta CURSOR_X 36 sta CURSOR_Y 37 sta SCREEN_PTR 38 lda #$10 39 sta SCREEN_PTR+1 40 41 rts 42