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⌂ ∞ ▽ Elite on the 6502

Loader: AllowJoystick

[Apple II version, Loader]

       Name: AllowJoystick                                           [Show more]
       Type: Subroutine
   Category: Loader
    Summary: An unused routine to check the joysticks and configure the title
             screen to check for the joystick fire button

    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file




.AllowJoystick

 LDA #0                 ; Set fireButtonMask to 0 to prevent the joystick fire
 STA fireButtonMask     ; button from being able to select joysticks on the
                        ; title screen

 LDA $C064              ; Set A to the value of the soft switch containing the
                        ; status of the joystick 0 x-axis (GC0)

 CMP #$FF               ; If it is not $FF then jump to joys1 to start the game
 BNE joys1              ; with the fire button disabled

 LDA $C065              ; Set A to the value of the soft switch containing the
                        ; status of the joystick 0 y-axis (GC1)

 CMP #$FF               ; If it is not $FF then jump to joys1 to start the game
 BNE joys1              ; with the fire button disabled

 LDA $C066              ; Set A to the value of the soft switch containing the
                        ; status of the joystick 1 x-axis (GC2)

 CMP #$FF               ; If it is not $FF then jump to joys1 to start the game
 BNE joys1              ; with the fire button disabled

 LDA $C067              ; Set A to the value of the soft switch containing the
                        ; status of the joystick 1 y-axis (GC3)

 CMP #$FF               ; If it is not $FF then jump to joys1 to start the game
 BNE joys1              ; with the fire button disabled

                        ; If we get here then all four joystick soft switches
                        ; are returning $FF

 LDA #$FF               ; Set fireButtonMask to $FF to allow the joystick fire
 STA fireButtonMask     ; button to select joysticks on the title screen

.joys1

 JMP startGame          ; Jump to startGame to start the game