git.sur5r.net Git - cc65/blob - libsrc/atari5200/joy/atr5200std.s

   1 ;
   2 ; Standard joystick driver for the Atari 5200.
   3 ;
   4 ; Christian Groessler, 2014-05-28
   5 ;
   6
   7         .include        "zeropage.inc"
   8
   9         .include        "joy-kernel.inc"
  10         .include        "joy-error.inc"
  11         .include        "atari5200.inc"
  12
  13         .macpack        module
  14
  15
  16 ; ------------------------------------------------------------------------
  17 ; Header. Includes jump table
  18
  19         module_header   _atr5200std_joy
  20
  21 ; Driver signature
  22
  23         .byte   $6A, $6F, $79           ; "joy"
  24         .byte   JOY_API_VERSION         ; Driver API version number
  25
  26 ; Library reference
  27
  28         .addr   $0000
  29
  30 ; Jump table.
  31
  32         .addr   INSTALL
  33         .addr   UNINSTALL
  34         .addr   COUNT
  35         .addr   READJOY
  36
  37 .code
  38
  39 ; ------------------------------------------------------------------------
  40 ; INSTALL routine. Is called after the driver is loaded into memory. If
  41 ; possible, check if the hardware is present and determine the amount of
  42 ; memory available.
  43 ; Must return an JOY_ERR_xx code in a/x.
  44 ;
  45
  46 INSTALL:
  47         lda     #JOY_ERR_OK
  48         ldx     #0
  49 ;       rts                     ; Run into UNINSTALL instead
  50
  51 ; ------------------------------------------------------------------------
  52 ; UNINSTALL routine. Is called before the driver is removed from memory.
  53 ; Can do cleanup or whatever. Must not return anything.
  54 ;
  55
  56 UNINSTALL:
  57         rts
  58
  59
  60 ; ------------------------------------------------------------------------
  61 ; COUNT: Return the total number of available joysticks in a/x.
  62 ;
  63
  64 COUNT:
  65         lda     $FD32           ; check ROM version
  66         cmp     #$E8
  67         bne     @2port
  68         lda     #4
  69         .byte   $2C             ; bit opcode, eats the next 2 bytes
  70 @2port: lda     #2
  71         ldx     #0
  72         rts
  73
  74 ; ------------------------------------------------------------------------
  75 ; READ: Read a particular joystick passed in A.
  76 ;
  77
  78 CENTER  =       228 / 2
  79 SENSIVITY       = 16
  80
  81 READJOY:
  82         and     #3              ; put joystick number in range, just in case
  83         tay
  84         asl     a
  85         tax                     ; Joystick number * 2 (0-6) into X, index into ZP shadow registers
  86
  87         lda     #0              ; Initialize return value
  88         cmp     TRIG0,y
  89         bne     @notrg
  90         lda     #$10            ; JOY_BTN
  91
  92 ; Read joystick
  93
  94 @notrg: ldy     PADDL0,x        ; get horizontal position
  95         cpy     #CENTER-SENSIVITY
  96         bcs     @chkleft
  97
  98         ora     #4              ; JOY_LEFT
  99         bne     @updown
 100
 101 @chkleft:
 102         cpy     #CENTER+SENSIVITY
 103         bcc     @updown
 104
 105         ora     #8              ; JOY_RIGHT
 106
 107 @updown:ldy     PADDL0+1,x      ; get vertical position
 108         cpy     #CENTER-SENSIVITY
 109         bcs     @chkdown
 110
 111         ora     #1              ; JOY_UP
 112         bne     @done
 113
 114 @chkdown:
 115         cpy     #CENTER+SENSIVITY
 116         bcc     @done
 117
 118         ora     #2              ; JOY_DOWN
 119
 120 @done:  rts