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68 lines
1.1 KiB
ArmAsm
68 lines
1.1 KiB
ArmAsm
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.include "atari5200.inc"
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SCREEN_BUF_SIZE = 20 * 24
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SCREEN_BUF = $4000 - SCREEN_BUF_SIZE
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.code
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.export screen_setup_20x24
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screen_setup_20x24:
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; initialize SAVMSC
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lda #<SCREEN_BUF
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sta SAVMSC
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lda #>SCREEN_BUF
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sta SAVMSC+1
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; initialize cursor position
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lda #0
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sta COLCRS_5200
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sta ROWCRS_5200
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; clear screen buffer
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ldy #<(SCREEN_BUF_SIZE-1)
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ldx #>(SCREEN_BUF_SIZE-1)
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clrscr: sta (SAVMSC),y
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dey
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cpy #$FF
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bne clrscr
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dex
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cpx #$FF
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bne clrscr
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; set display list
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lda #<dlist
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sta SDLSTL
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lda #>dlist
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sta SDLSTH
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rts
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.segment "RODATA"
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; display list for 20x24 text mode
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dlist: .repeat 3
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.byte DL_BLK8
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.endrepeat
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.byte DL_CHR20x8x2 | DL_LMS
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.word SCREEN_BUF
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.repeat 23
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.byte DL_CHR20x8x2
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.endrepeat
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.byte DL_JVB
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.word dlist
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; end of display list
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.assert ((* >> 10) = (dlist >> 10)), error, "Display list crosses 1K boundary"
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.end
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