cc65/libsrc/geos-cbm/joy/geos-stdjoy.s

;
; Standard joystick driver for the C64. May be used multiple times when linked
; to the statically application.
;
; Ullrich von Bassewitz, 2002-12-20
;

            .include "zeropage.inc"
            .include "joy-kernel.inc"
            .include "joy-error.inc"
            .include "geossym.inc"

            .macpack generic
            .macpack module


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

        module_header   _geos_stdjoy_joy

; Driver signature

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

; Library reference

        .addr   $0000

; Jump table.

        .word INSTALL
        .word UNINSTALL
        .word COUNT
        .word READ

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

JOY_COUNT       = 2             ; Number of joysticks we support

; ------------------------------------------------------------------------
; Data.

.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
        .assert JOY_ERR_OK = 0, error
        tax
;       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 #>JOY_COUNT
        rts

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

READ:
        tax
        php
        sei                     ; disable IRQ
        lda $01
        pha
        lda #$35
        sta $01                 ; enable I/O

        txa                     ; Joystick number into X
        bne joy2

; Read joystick 1

joy1:
        lda #$7F
        sta cia1base
        lda cia1base+1
back:   tay
        pla
        sta $01
        plp
        tya
        and #$1F
        eor #$1F
        rts

; Read joystick 2

joy2:   ldx #0
        lda #$E0
        ldy #$FF
        sta cia1base+2
        lda cia1base+1
        sty cia1base+2
        jmp back