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⌂ ∞ Elite on the BBC Micro and NES

Keyboard: DOKEY

[Elite-A, Parasite]

       Name: DOKEY                                                   [Show more]
       Type: Subroutine
   Category: Keyboard
    Summary: Scan for the seven primary flight controls and apply the docking
             computer manoeuvring code
  Deep dive: The key logger
             The docking computer

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT17 calls DOKEY




.DOKEY

 LDA JSTK               \ If JSTK is zero, then we are configured to use the
 BEQ DK4                \ keyboard rather than the joystick, so jump to DK4 to
                        \ scan for pause, configuration and secondary flight
                        \ keys

 LDX #1                 \ Call DKS2 to fetch the value of ADC channel 1 (the
 JSR DKS2               \ joystick X value) into (A X), and OR A with 1. This
 ORA #1                 \ ensures that the high byte is at least 1, and then we
 STA JSTX               \ store the result in JSTX

 LDX #2                 \ Call DKS2 to fetch the value of ADC channel 2 (the
 JSR DKS2               \ joystick Y value) into (A X), and EOR A with JSTGY.
 EOR JSTGY              \ JSTGY will be &FF if the game is configured to
 STA JSTY               \ reverse the joystick Y channel, so this EOR does
                        \ exactly that, and then we store the result in JSTY

                        \ Fall through into DK4 to scan for other keys