git.sur5r.net Git - cc65/blob - libsrc/nes/get_tv.s

   1 ;
   2 ; Stefan Haubenthal, 2007-01-21
   3 ;
   4 ; unsigned char get_tv (void);
   5 ; /* Return the video mode the machine is using */
   6 ;
   7
   8         .include        "nes.inc"
   9         .include        "get_tv.inc"
  10         .importzp       tmp1, tmp2
  11
  12 ;--------------------------------------------------------------------------
  13 ; _get_tv
  14
  15 .proc   _get_tv
  16
  17         lda     #TV::NTSC       ; assume NTSC
  18         tax                     ; clear
  19         sta     tmp1
  20         sta     tmp2
  21         ldy     tickcount
  22 wait:   cpy     tickcount
  23         beq     wait
  24         iny                     ; next tick
  25 loop:   cpy     tickcount
  26         bne     over
  27         inc     tmp1
  28         bne     loop
  29         inc     tmp2
  30         bne     loop
  31 over:   ldy     tmp2
  32         cpy     #9
  33         bcc     nopal
  34         lda     #TV::PAL        ; choose PAL
  35 nopal:  rts
  36
  37 .endproc