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117 lines
3.5 KiB
ArmAsm
117 lines
3.5 KiB
ArmAsm
;
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; Standard joystick driver for the VIC20. May be used multiple times when linked
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; to the statically application.
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;
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; Ullrich von Bassewitz, 2002-12-20
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; Using code from Steve Schmidtke
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;
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.include "zeropage.inc"
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.include "joy-kernel.inc"
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.include "joy-error.inc"
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.include "vic20.inc"
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.macpack generic
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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.segment "JUMPTABLE"
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; Driver signature
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.byte $6A, $6F, $79 ; "joy"
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.byte JOY_API_VERSION ; Driver API version number
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; Button state masks (8 values)
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.byte $02 ; JOY_UP
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.byte $04 ; JOY_DOWN
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.byte $08 ; JOY_LEFT
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.byte $80 ; JOY_RIGHT
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.byte $10 ; JOY_FIRE
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.byte $00 ; JOY_FIRE2 unavailable
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.byte $00 ; Future expansion
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.byte $00 ; Future expansion
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; Jump table.
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.addr INSTALL
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.addr UNINSTALL
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.addr COUNT
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.addr READ
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.addr 0 ; IRQ entry unused
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; ------------------------------------------------------------------------
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; Constants
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JOY_COUNT = 1 ; Number of joysticks we support
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; ------------------------------------------------------------------------
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; Data.
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.code
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; ------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. If
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; possible, check if the hardware is present and determine the amount of
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; memory available.
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; Must return an JOY_ERR_xx code in a/x.
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;
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INSTALL:
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lda #<JOY_ERR_OK
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ldx #>JOY_ERR_OK
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; rts ; Run into UNINSTALL instead
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; ------------------------------------------------------------------------
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; UNINSTALL routine. Is called before the driver is removed from memory.
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; Can do cleanup or whatever. Must not return anything.
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;
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UNINSTALL:
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rts
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; ------------------------------------------------------------------------
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; COUNT: Return the total number of available joysticks in a/x.
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;
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COUNT:
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lda #<JOY_COUNT
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ldx #>JOY_COUNT
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rts
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; ------------------------------------------------------------------------
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; READ: Read a particular joystick passed in A.
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; The current implemenation will ignore the joystick number because we do only
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; have one joystick
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READ: lda #$7F ; mask for VIA2 JOYBIT: sw3
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ldx #$C3 ; mask for VIA1 JOYBITS: sw0,sw1,sw2,sw4
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sei ; necessary?
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ldy VIA2_DDRB ; remember the date of DDRB
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sta VIA2_DDRB ; set JOYBITS on this VIA for input
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lda VIA2_JOY ; read JOYBIT: sw3
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sty VIA2_DDRB ; restore the state of DDRB
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asl ; Shift sw3 into carry
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ldy VIA1_DDRA ; remember the state of DDRA
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stx VIA1_DDRA ; set JOYBITS on this VIA for input
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lda VIA1_JOY ; read JOYBITS: sw0,sw1,sw2,sw4
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sty VIA1_DDRA ; restore the state of DDRA
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cli ; necessary?
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ror ; Shift sw3 into bit 7
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and #$9E ; Mask relevant bits
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eor #$9E ; Active states are inverted
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rts
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