cc65/libsrc/nes/joy/nes-stdjoy.s

;
; Standard joypad driver for the NES. May be used multiple times when
; linked to the statically application.
;
; Ullrich von Bassewitz, 2003-05-02
; Stefan Haubenthal, 2004-10-05
;

        .include        "zeropage.inc"

        .include        "joy-kernel.inc"
        .include        "joy-error.inc"
        .include        "nes.inc"

        .macpack        module


; ------------------------------------------------------------------------
; Header. Includes jump table

        module_header   _nes_stdjoy_joy

; Driver signature

        .byte   $6A, $6F, $79           ; "joy"
        .byte   JOY_API_VERSION         ; Driver API version number

; Library reference

        .addr   $0000

; Button state masks (8 values)

        .byte   $10                     ; JOY_UP
        .byte   $20                     ; JOY_DOWN
        .byte   $40                     ; JOY_LEFT
        .byte   $80                     ; JOY_RIGHT
        .byte   $01                     ; JOY_FIRE      (A)
        .byte   $02                     ; JOY_FIRE2     (B)
        .byte   $04                     ;               (Select)
        .byte   $08                     ;               (Start)

; Jump table.

        .addr   INSTALL
        .addr   UNINSTALL
        .addr   COUNT
        .addr   READJOY
        .addr   0                       ; IRQ entry unused

; ------------------------------------------------------------------------
; Constants

JOY_COUNT       = 2             ; Number of joysticks we support


.code

; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. If
; possible, check if the hardware is present and determine the amount of
; memory available.
; Must return an JOY_ERR_xx code in a/x.
;

INSTALL:
        lda     #JOY_ERR_OK
        ldx     #0
;       rts                     ; Run into UNINSTALL instead

; ------------------------------------------------------------------------
; UNINSTALL routine. Is called before the driver is removed from memory.
; Can do cleanup or whatever. Must not return anything.
;

UNINSTALL:
        rts


; ------------------------------------------------------------------------
; COUNT: Return the total number of available joysticks in a/x.
;

COUNT:
        lda     #JOY_COUNT
        ldx     #0
        rts

; ------------------------------------------------------------------------
; READ: Read a particular joystick passed in A.
;

READJOY:
        and     #$01            ; Fix joystick number
        tay                     ; Joystick number (0,1) into Y

        lda     #1
        sta     APU_PAD1,y
        lda     #0
        sta     APU_PAD1,y

; Read joystick

        ldx     #8
@Loop:  lda     APU_PAD1,y
        ror     a
        ror     tmp1
        dex
        bne     @Loop

        lda     tmp1
;       ldx     #$00            ; X implicitly fixed
        rts