git.sur5r.net Git - cc65/blob - libsrc/creativision/joy.s

   1 ;*
   2 ;* Creativision Joystick Function
   3 ;*
   4 ;* unsigned char __fastcall__ joystate(unsigned char joy);
   5 ;*
   6 ;* JOY_1 -> Return Left Joystick direction
   7 ;* JOY_2 -> Return Right Joystick direction
   8 ;* JOY_3 -> Return Left Joystick buttons
   9 ;* JOY_4 -> Return Right Joystick buttons
  10 ;*
  11 ;* Will only work if interrupts are enabled.
  12
  13         .export         _joystate
  14         .include        "creativision.inc"
  15
  16 _joystate:
  17         cmp             #1      ; Left Direction
  18         bne             l1
  19
  20         lda             $11
  21         beq             l5
  22         and             #$0F
  23         lsr             a
  24         tax
  25         inx
  26         txa
  27         rts
  28
  29 l1:     cmp             #2      ; Right Direction
  30         bne             l2
  31
  32         lda             $13
  33         beq             l5
  34         and             #$0F
  35         lsr             a
  36         tax
  37         inx
  38         txa
  39         rts
  40
  41 l2:     cmp             #3      ; Left Buttons
  42         bne             l3
  43
  44         lda             $16
  45         beq             l5
  46         and             #$0F
  47         rts
  48
  49 l3:     cmp             #4
  50         bne             l4
  51
  52         lda             $17
  53         beq             l5
  54         and             #$0F
  55         rts
  56
  57 l4:     lda             #0
  58 l5:     rts