;Joystick Constants and Functions for Commander X16 Computer

;NOTE: As of R35, joystick_scan() has not been added to the
;vsync() interrupt routine. This will be in R36, so development
;on this module is currently on hold

        SUBR  _JOYSTK

JYSTKS  EQU 2       ;Number of Joysticks

JOY0    EQU $A031   ;Joystick 0 Status
JOY1    EQU $A034   ;Joystick 1 Status

;Joystick Bit Masks
JOYUP   EQU $08     ;Up    
JOYDN   EQU $04     ;Down  
JOYLF   EQU $02     ;Left  
JOYRT   EQU $01     ;Right 
JOYB0   EQU $C0     ;Button

;Extended Bit Masks
JOYBA   EQU $80     ;A Button
JOYBB   EQU $40     ;B Button
JOYSL   EQU $20     ;Select
JOYST   EQU $10     ;Start
JOYBL   EQU $08     ;Left Button
JOYBR   EQU $04     ;Right Button
JOYBX   EQU $02     ;X Button
JOYBY   EQU $01     ;Y Button

;Controller Types
JOYKBD  EQU $00     ;Keyboard (NES Emulation)
JOYNES  EQU $01     ;NES Controller
JOYSNS  EQU $02     ;SNS Controller

;joytsk(j) - Read Joystick
;Args: A = Joystick Number (0 or 1)
;Sets: TEMP0 = Inverted Controller Status
;      TEMP1 = Inverted Extended Status
;      TEMP2 - Extended Result (Buttons)
;Destroys: TEMP3
;Returns: A = Joystick Status (Joystick Bit Masks
;             The Joystick Button is mapped to
;             A,B on the NES Controller and
;             A,B,X,Y on the SNES Controller
;         Y = Extended Status (Extended Bit Masks)
;             Used with Extended Bitmasks to check
;             A,B,X,Y,Select, Start, Left and Right
;         X = Controller Type (0=Keyboard, 1=NES, 2=SNES)
JOYSTK: CMP #JYSTKS       ;If Invalid Joystick Number
        BCS .JOYSTE       ;  Return ERROR
        JSR JOYGET        ;Read Joystick State
        EOR #$FF          ;Invert Controller Status
        STA TEMP0         ;and Save in TEMP0
        STX TEMP1         ;Save Extended Status in TEMP1
        TYA               ;If Controller Not Present
        BNE .JOYSTF       ;  Return $FF, $FF, $FF
;JOYEXT                   ;Process Extended Bits
        STZ TEMP3         ;Clear Button Mask
        LDA TEMP1         ;Get Extended Status
        BIT #$0E          ;Check Bits 1 - 3
        BNE .JOYSNS       ;If NES/Keyboard        
;JOYNES                   ;  Process NES Buttons
        EOR #$01          ;  Invert Extended Bit 0
        TAX               ;    and Copy to X
        LDA TEMP0         ;  Get Controller Status
        AND #$F0          ;    Isolate Bits 4-7
        TAY               ;    and Copy Back to Y
        BRA .JOYSTX       ;Else
.JOYSNS                   ;  Process SNES Buttons
        LDX #2            ;  Set Controller Type to 2
        LDA TEMP1         ;    and Save Result
        AND #$C0          ;  Isolate SNES A,X Buttons
        STA TEMP3         ;  and Save in Button Mask
        LDA TEMP1         ;  Retrieve Extended Buttons
        AND #$30          ;  Isolate L and R
        ASL               ;  and Shift to Bits 2 and 3
        ASL                  
        BIT TEMP1         ;  Get Ext Status High Bits
        BCC +2            ;  If Extended Bit 7 was Set
        ORA #$80          ;    Set Buttons Bit 7 (A)
        BVC +2            ;  If Extended Bit 6 was Set
        ORA #$20          ;    Set Buttons Bit 1 (X)
        STA TEMP2         ;  Save Buttons A,X,L,R
        LDA TEMP0         ;  Retrieve Controller Status
        AND #$30          ;  Isolate Select and Start
        ORA TEMP2         ;  Combine with A,X,L,R
        BIT TEMP2         ;  Get Status High Bits
        BCC +2            ;  If Status Bit 7 was Set
        ORA #$40          ;    Set Buttons Bit 6 (B)
        BVC +2            ;  If Status Bit 6 was Set
        ORA #$01          ;    Set Buttons Bit 0 (Y)
        STA TEMP2         ;  Save Buttons in TEMP2
        TAY               ;    and Copy to Y
.JOYSTX                   ;Build Joystick Status
        LDA TEMP0         ;   Restore Controller Status
        ORA TEMP3         ;   Combine Buttons
        AND #$CF          ;   Mask off Select and Start
        RTS
.JOYSTE                   ;Return Error
        LDA #$FF          ;Return $FF, $FF, $FF
        TAY
.JOYSTF TAX               ;A, Y already $FF
        RTS

;joyscn() - Queries the Joysticks and Saves their State
;Note: The default interrupt handler already takes care 
;of this, so this routine should only be called if the 
;interrupt handler has been completely replaced.
JOYSCN  EQU $FF53   ;Kernal joystick_scan Routine

;joyget(j) - Get State of Joystick Number j
;Args: A = Joystick Number (0 or 1)
;Returns: A = Joystick Status Bits
;                  | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
;             NES  | A | B |SEL|STA|UP |DN |LT |RT |
;             SNES | B | Y |SEL|STA|UP |DN |LT |RT |
;         X = Joystick Extended Status Bits
;                  | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
;             NES  | 0 | 0 | 0 | 0 | 0 | 0 | 0 |KBD|
;             SNES | A | X | L | R | 1 | 1 | 1 | 1 |
;         Y = Joystick Present
;             $00 = Joystick Present
;             $FF = Joystick Not Present
;Note: Status Bits will be 0 if Pressed, 1 if Not
JOYGET  EQU $FF56   ;Kernal joystick_get Routine