;Paddle Controller Constants and Functions for Atari 400 & 800

PADDLS  EQU #$08      ;Maximum Numbers of Paddles

;Read Paddle
;Args: A = Paddle #
;Affects: X
;Returns: A = Paddle Value
;             0 and Carry Set if Paddle # Invalid
PADDLE: CMP #PADDLS     ;If Invalid Paddle #
        BCS BUTTOZ      ;  Return 0 & Carry Set
        TAX             ;Copy Paddle # to X
        LDA $0270,X     ;Read Paddle Shadow Register
        RTS

BUTTNS  EQU #$04      ;Maximum Numbers of Paddle Buttons

;Read Paddle Button
;Args: A = Button #
;Affects: X,Y
;Returns: A = $FF if Paddle Button Pressed
;             $00 if Paddle Button Not Pressed
;         Carry Set if Button Number Invalid
BUTTON: CMP #BUTTNS     ;If Button# >= # of Buttons
        BCS BUTTOZ      ;  Return FALSE & Carry Set
        TAX             ;and Copy to X Register
        LDA $027C,Y     ;Read Button Shadow Register
        AND #$01        ;Mask off Relevant Bit
        BNE BUTTOZ      ;If Bit is 0
        LDA #$FF        ;  Return TRUE
        RTS             ;Else
BUTTOZ: LDA #$00        ;  Return FALSE
        RTS