2013-12-05 11:40:44 +00:00
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;*
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;* clrscr
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;*
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;* NB: All screen functions assume Graphics Mode 1 in a default configuration.
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;* Therefore, this is hard coded to use $1000-$12FF as screen VRAM.
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2017-02-01 18:46:04 +00:00
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.export _clrscr
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.include "creativision.inc"
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2013-12-05 11:40:44 +00:00
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_clrscr:
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2017-02-01 18:46:04 +00:00
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sei ; Disable interrupts. Default INT handler reads VDP_STATUS
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; and would lose any setup done here.
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lda #$00 ; VRAM offset low
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sta VDP_CONTROL_W
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lda #$50 ; VRAM offset high ($10 OR $40)
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sta VDP_CONTROL_W
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lda #$C0 ; Space from ROM setup
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ldx #0
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ldy #3
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L1: sta VDP_DATA_W
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inx
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bne L1
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dey
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bne L1
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cli ; Let interrupts go again
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lda #0
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sta CURSOR_X
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sta CURSOR_Y
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sta <SCREEN_PTR
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lda #$10
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sta >SCREEN_PTR
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rts
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