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28 lines
1.0 KiB
Plaintext
28 lines
1.0 KiB
Plaintext
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;C02 VCS Library - Joystick Assembly Language Subroutines
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;getstk(cntrlr) - Read Joystick
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;Args: A = Controller Number, 0=Left, 1=Right
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;Sets: TEMP0 = Left Joystick Raw Directional Bits
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; TEMP1 = Right Joystick Raw Directional Bits
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; X = Controller Number
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;Returns: A = Joystick Bits (1 if Pressed)
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; 0=Up, 1=Down, 2=Left, 3=Right, 7=Trigger
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; N = Set if Trigger Pressed
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; Z = Set if No Buttons or Trigger Pressed
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GETSTK: TAX ;Save Stick Number in Index
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LDA SWCHA ;Read Joystick Register
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LSR ;Shift High Nybble into Low Nybble
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LSR
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LSR
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LSR
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STA TEMP0 ;Save Left Joystick Raw Bits
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LDA SWCHA ;Read Joystick Register
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AND #$0F ;Strip High Nybble
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STA TEMP1 ;Save Right Joystick Raw Bits
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LDA INPT4,X ;Read Joystick Trigger
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AND #$80 ;Strip Bits 1-6
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ORA TEMP0,X ;Combine with Directional Bits
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EOR #$8F ;Reverse Bits
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RTS
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