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a3d8829be9
This change includes some cleanups, removal of mainargs.s (game console programs never have arguments), and a workaround for a problem I'm seeing. The problem is that sometimes (in fact, more often than not) the clrscr() call in testcode/lib/joy-test.c writes some garbage chars on the screen (most often a "P"). Could be my hardware (I haven't seen it on MAME), but to me the root cause is still unknown.
42 lines
948 B
ArmAsm
42 lines
948 B
ArmAsm
;*
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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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.export _clrscr
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.include "creativision.inc"
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_clrscr:
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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 #$40 ; Space char 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+1
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rts
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