git.sur5r.net Git - cc65/blob - libsrc/atari5200/conioscreen.s

   1
   2                 .include "atari5200.inc"
   3
   4 SCREEN_BUF_SIZE =       20 * 24
   5 SCREEN_BUF      =       $4000 - SCREEN_BUF_SIZE
   6
   7                 .code
   8                 .export screen_setup_20x24
   9
  10 screen_setup_20x24:
  11
  12                 ; initialize SAVMSC
  13                 lda     #<SCREEN_BUF
  14                 sta     SAVMSC
  15                 lda     #>SCREEN_BUF
  16                 sta     SAVMSC+1
  17
  18                 ; initialize cursor position
  19                 lda     #0
  20                 sta     COLCRS_5200
  21                 sta     ROWCRS_5200
  22
  23                 ; clear screen buffer
  24                 ldy     #<(SCREEN_BUF_SIZE-1)
  25                 ldx     #>(SCREEN_BUF_SIZE-1)
  26 clrscr:         sta     (SAVMSC),y
  27                 dey
  28                 cpy     #$FF
  29                 bne     clrscr
  30                 dex
  31                 cpx     #$FF
  32                 bne     clrscr
  33
  34                 ; set display list
  35
  36                 lda     #<dlist
  37                 sta     SDLSTL
  38                 lda     #>dlist
  39                 sta     SDLSTH
  40
  41                 rts
  42
  43
  44                 .segment "RODATA"
  45
  46 ; display list for 20x24 text mode
  47
  48 dlist:          .repeat 3
  49                 .byte   DL_BLK8
  50                 .endrepeat
  51
  52                 .byte   DL_CHR20x8x2 | DL_LMS
  53                 .word   SCREEN_BUF
  54
  55                 .repeat 23
  56                 .byte   DL_CHR20x8x2
  57                 .endrepeat
  58
  59                 .byte  DL_JVB
  60                 .word   dlist
  61
  62 ; end of display list
  63
  64 .assert ((* >> 10) = (dlist >> 10)), error, "Display list crosses 1K boundary"
  65
  66
  67                 .end