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35 lines
1.1 KiB
Plaintext
35 lines
1.1 KiB
Plaintext
;Paddle Controller Constants and Functions for Apple II
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PADDLS EQU 4 ;Maximum Numbers of Paddles
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;paddle(n) - Read Paddle n
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;Args: A = Paddle Number (0-3)
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;Returns: A, Y = Paddle Value (0-255)
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; Carry Set if P
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PADDLE: LDY #0 ;Set Result to 0
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CMP #PADDLS ;If Paddle# >= Max
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BCS PADDLZ ; Return 0 & Carry Set
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TAX ;Copy Paddle# to X Register
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JSR $FB1E ;Execute Monitor PREAD Routine
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PADDLZ: TYA ;Copy Result to Accumulator
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RTS
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BUTTNS EQU 2 ;Maximum Numbers of Buttons
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;button(n) - Read Paddle Button n
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;Args: A = Button Number (0-1)
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;Returns: A, Y = Button State
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; 0 = Not Pressed
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; $FF = Pressed
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; X = Button Number
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; Carry Set if P
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BUTTON: LDY #0 ;Set Result to 0
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CMP #BUTTNS ;If Button# >= Max
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BCS BUTTOZ ; Return Zero & Carry Set
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TAX ;Copy Paddle# to X Register
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LDA $C061,X ;Load Button Register
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BPL BUTTOZ ;If Bit 7 Set
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DEY ; Change Result to $FF
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BUTTOZ: TYA ;Copy Result to Accumulator
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RTS
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