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https://github.com/cc65/cc65.git
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73 lines
1.3 KiB
ArmAsm
73 lines
1.3 KiB
ArmAsm
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; Written by Groepaz/Hitmen <groepaz@gmx.net>
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; Cleanup by Ullrich von Bassewitz <uz@cc65.org>
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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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.import ppubuf_waitempty
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.include "nes.inc"
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.proc _clrscr
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; wait until all console data has been written
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jsr ppubuf_waitempty
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; wait for vblank
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lda #0
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sta VBLANK_FLAG
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@w2: lda VBLANK_FLAG
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beq @w2
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; switch screen off
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lda #%00000000
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sta PPU_CTRL2
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; Set start address to Name Table #1
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lda #$20
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sta PPU_VRAM_ADDR2
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lda #$00
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sta PPU_VRAM_ADDR2
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; Clear Name Table #1
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lda #' '
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ldx #$f0 ; 4*$f0=$03c0
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beg: sta PPU_VRAM_IO
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sta PPU_VRAM_IO
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sta PPU_VRAM_IO
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sta PPU_VRAM_IO
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dex
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bne beg
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lda #$23 ;
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sta PPU_VRAM_ADDR2 ; Set start address to PPU address $23C0
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lda #$C0 ; (1st attribute table)
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sta PPU_VRAM_ADDR2
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ldx #$00
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lll: lda #$00 ; Write attribute table value and auto increment
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sta PPU_VRAM_IO ; to next address
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inx
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cpx #$40
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bne lll
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; switch screen on again
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lda #%00011110
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sta PPU_CTRL2
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rts
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.endproc
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