Version analysis of DOKEY

Cassette, Electron
Docked
Flight, 6502SP, Master
    Summary: Scan for the seven primary flight controls
  Deep dive: The key logger
             The docking computer
    Summary: Scan for the joystick
    Summary: Scan for the seven primary flight controls and apply the docking
             computer manoeuvring code
  Deep dive: The key logger
             The docking computer

Cassette, Flight, 6502SP, Master
Electron
 Scan for the seven primary flight controls (or the equivalent on joystick),
 pause and configuration keys, and secondary flight controls, and update the
 key logger accordingly. Specifically:

   * If we are on keyboard configuration, clear the key logger and update it
     for the seven primary flight controls, and update the pitch and roll
     rates accordingly.

   * If we are on joystick configuration, clear the key logger and jump to
     DKJ1, which reads the joystick equivalents of the primary flight
     controls.

 Both options end up at DK4 to scan for other keys, beyond the seven primary
 flight controls.
 Scan for the seven primary flight controls, pause and configuration keys, and
 secondary flight controls, and update the key logger and pitch and roll rates
 accordingly.

 Unlike the other versions of Elite, the Electron version doesn't actually read
 the joystick values from the ADC channels, so although you can configure
 joysticks using the "K" option when paused, they won't have any effect. All
 the other joystick code is present, though, so perhaps the intention was to
 support joysticks at some point?

Flight, 6502SP
 Other entry points:

   auton                Get the docking computer to "press" the flight keys to
                        dock the ship

6502SP
 LDA NEEDKEY            \ If NEEDKEY is zero, skip the next instruction
 BEQ P%+5

 JSR RDKEY              \ NEEDKEY is non-zero, so call RDKEY to ask the I/O
                        \ processor to scan the keyboard for key presses and
                        \ update the key logger buffer at KTRAN

 LDA #&FF               \ Set NEEDKEY to &FF, so the next call to DOKEY updates
 STA NEEDKEY            \ the key logger buffer

Cassette, Flight, 6502SP
Docked
Electron
 JSR U%                 \ Call U% to clear the key logger

 LDA JSTK               \ If JSTK is non-zero, then we are configured to use
 BNE DKJ1               \ the joystick rather than keyboard, so jump to DKJ1
                        \ to read the joystick flight controls, before jumping
                        \ to DK4 to scan for pause, configuration and secondary
                        \ flight keys
 LDA JSTK               \ If JSTK is zero, then we are configured to use the
 BEQ DK9                \ keyboard rather than the joystick, so jump to DK9 to
                        \ make sure the Bitstik is disabled as well (DK9 then
                        \ jumps 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
 JSR U%                 \ Call U% to clear the key logger

Flight, 6502SP
 STA BSTK               \ Set BSTK = 0 to disable the Bitstik

Cassette, Flight
Master
6502SP
Electron
 LDY #7                 \ We're going to work our way through the primary flight
                        \ control keys (pitch, roll, speed and laser), so set a
                        \ counter in Y so we can loop through all 7

.DKL2

 JSR DKS1               \ Call DKS1 to see if the KYTB key at offset Y is being
                        \ pressed, and set the key logger accordingly

 DEY                    \ Decrement the loop counter

 BNE DKL2               \ Loop back for the next key, working our way from A at
                        \ KYTB+7 down to ? at KYTB+1
 JSR RDKEY-1            \ Scan the keyboard for a key press and return the
                        \ ASCII code of the key pressed in X
 LDX #7                 \ We're now going to copy key press data for the primary
                        \ flight keys from the key logger buffer at KTRAN to the
                        \ key logger at KL, so set a loop counter in X so we can
                        \ count down from KTRAN + 7 to KTRAN + 1

.DKL2

 LDA KTRAN,X            \ Copy the X-th byte of KTRAN to the X-th byte of KL
 STA KL,X

 DEX                    \ Decrement the loop counter

 BNE DKL2               \ Loop back until we have copied all seven primary
                        \ flight control key presses to KL
 LDY #7                 \ We're going to work our way through the primary flight
                        \ control keys (pitch, roll, speed and laser), so set a
                        \ counter in Y so we can loop through all 7

.DKL2

 LDX KYTB,Y             \ Call DKS4 to see if the KYTB key at offset Y is being
 JSR DKS4               \ pressed

 BPL P%+6               \ If the key isn't being pressed, skip the following two
                        \ instructions

 LDX #&FF               \ Set the key logger for this key to indicate it's being
 STX KL,Y               \ pressed

 DEY                    \ Decrement the loop counter

 BNE DKL2               \ Loop back for the next key, working our way from A at
                        \ KYTB+7 down to ? at KYTB+1

Flight, 6502SP
Master
 LDA auto               \ If auto is 0, then the docking computer is not
 BEQ DK15               \ currently activated, so jump to DK15 to skip the
                        \ docking computer manoeuvring code below

.auton
 LDA auto               \ If auto is 0, then the docking computer is not
 BEQ DK15               \ currently activated, so jump to DK15 to skip the
                        \ docking computer manoeuvring code below

Flight, 6502SP, Master
 JSR ZINF               \ Call ZINF to reset the INWK ship workspace

 LDA #96                \ Set nosev_z_hi = 96
 STA INWK+14

 ORA #%10000000         \ Set sidev_x_hi = -96
 STA INWK+22

 STA TYPE               \ Set the ship type to -96, so the negative value will
                        \ let us check in the DOCKIT routine whether this is our
                        \ ship that is activating its docking computer, rather
                        \ than an NPC ship docking

 LDA DELTA              \ Set the ship speed to DELTA (our speed)
 STA INWK+27

 JSR DOCKIT             \ Call DOCKIT to calculate the docking computer's moves
                        \ and update INWK with the results

                        \ We now "press" the relevant flight keys, depending on
                        \ the results from DOCKIT, starting with the pitch keys

 LDA INWK+27            \ Fetch the updated ship speed from byte #27 into A

 CMP #22                \ If A < 22, skip the next instruction
 BCC P%+4

 LDA #22                \ Set A = 22, so the maximum speed during docking is 22

 STA DELTA              \ Update DELTA to the new value in A

 LDA #&FF               \ Set A = &FF, which we can insert into the key logger
                        \ to "fake" the docking computer working the keyboard

Flight, 6502SP
Master
 LDX #0                 \ Set X = 0, so we "press" KY1 below ("?", slow down)
 LDX #15                \ Set X = 0, so we "press" KY+15, i.e. KY1, below
                        \ ("?", slow down)

Flight, 6502SP, Master
 LDY INWK+28            \ If the updated acceleration in byte #28 is zero, skip
 BEQ DK11               \ to DK11

Flight, 6502SP
Master
 BMI P%+3               \ If the updated acceleration is negative, skip the
                        \ following instruction

 INX                    \ The updated acceleration is positive, so increment X
                        \ to 1, so we "press" KY2 below (Space, speed up)

 STA KY1,X              \ Store &FF in either KY1 or KY2 to "press" the relevant
                        \ key, depending on whether the updated acceleration is
                        \ negative (in which case we "press" KY1, "?", to slow
                        \ down) or positive (in which case we "press" KY2,
                        \ Space, to speed up)
 BMI P%+4               \ If the updated acceleration is negative, skip the
                        \ following instruction

 LDX #11                \ Set X = 11, so we "press" KY+11, i.e. KY2, with the
                        \ next instruction (Space, speed up)

 STA KL,X               \ Store &FF in either KY1 or KY2 to "press" the relevant
                        \ key, depending on whether the updated acceleration is
                        \ negative (in which case we "press" KY1, "?", to slow
                        \ down) or positive (in which case we "press" KY2,
                        \ Space, to speed up)

Flight, 6502SP, Master
.DK11

                        \ We now "press" the relevant roll keys, depending on
                        \ the results from DOCKIT

 LDA #128               \ Set A = 128, which indicates no change in roll when
                        \ stored in JSTX (i.e. the centre of the roll indicator)

Flight, 6502SP
Master
 LDX #0                 \ Set X = 0, so we "press" KY3 below ("<", increase
                        \ roll)
 LDX #13                \ Set X = 13, so we "press" KY+13, i.e. KY3, below
                        \ ("<", increase roll)

Flight, 6502SP, Master
 ASL INWK+29            \ Shift ship byte #29 left, which shifts bit 7 of the
                        \ updated roll counter (i.e. the roll direction) into
                        \ the C flag

 BEQ DK12               \ If the remains of byte #29 is zero, then the updated
                        \ roll counter is zero, so jump to DK12 set JSTX to 128,
                        \ to indicate there's no change in the roll

Flight, 6502SP
Master
 BCC P%+3               \ If the C flag is clear, skip the following instruction

 INX                    \ The C flag is set, i.e. the direction of the updated
                        \ roll counter is negative, so increment X to 1 so we
                        \ "press" KY4 below (">", decrease roll)
 BCC P%+4               \ If the C flag is clear, skip the following instruction

 LDX #14                \ The C flag is set, i.e. the direction of the updated
                        \ roll counter is negative, so set X to 14 so we
                        \ "press" KY+14. i.e. KY4, below (">", decrease roll)

Flight, 6502SP, Master
 BIT INWK+29            \ We shifted the updated roll counter to the left above,
 BPL DK14               \ so this tests bit 6 of the original value, and if it
                        \ is clear (i.e. the magnitude is less than 64), jump to
                        \ DK14 to "press" the key and leave JSTX unchanged

 LDA #64                \ The magnitude of the updated roll is 64 or more, so
 STA JSTX               \ set JSTX to 64 (so the roll decreases at half the
                        \ maximum rate)

 LDA #0                 \ And set A = 0 so we do not "press" any keys (so if the
                        \ docking computer needs to make a serious roll, it does
                        \ so by setting JSTX directly rather than by "pressing"
                        \ a key)

.DK14

Flight, 6502SP
Master
 STA KY3,X              \ Store A in either KY3 or KY4, depending on whether
                        \ the updated roll rate is increasing (KY3) or
                        \ decreasing (KY4)
 STA KL,X               \ Store A in either KY3 or KY4, depending on whether
                        \ the updated roll rate is increasing (KY3) or
                        \ decreasing (KY4)

Flight, 6502SP, Master
 LDA JSTX               \ Fetch A from JSTX so the next instruction has no
                        \ effect

.DK12

 STA JSTX               \ Store A in JSTX to update the current roll rate

                        \ We now "press" the relevant pitch keys, depending on
                        \ the results from DOCKIT

 LDA #128               \ Set A = 128, which indicates no change in pitch when
                        \ stored in JSTX (i.e. the centre of the pitch
                        \ indicator)

Flight, 6502SP
Master
 LDX #0                 \ Set X = 0, so we "press" KY5 below ("X", decrease
                        \ pitch, pulling the nose up)
 LDX #6                 \ Set X = 6, so we "press" KY+6, i.e. KY5, below
                        \ ("X", decrease pitch, pulling the nose up)

Flight, 6502SP, Master
 ASL INWK+30            \ Shift ship byte #30 left, which shifts bit 7 of the
                        \ updated pitch counter (i.e. the pitch direction) into
                        \ the C flag

 BEQ DK13               \ If the remains of byte #30 is zero, then the updated
                        \ pitch counter is zero, so jump to DK13 set JSTY to
                        \ 128, to indicate there's no change in the pitch

Flight, 6502SP
Master
 BCS P%+3               \ If the C flag is set, skip the following instruction

 INX                    \ The C flag is clear, i.e. the direction of the updated
                        \ pitch counter is positive (dive), so increment X to 1
                        \ so we "press" KY6 below ("S", increase pitch, so the
                        \ nose dives)

 STA KY5,X              \ Store 128 in either KY5 or KY6 to "press" the relevant
                        \ key, depending on whether the pitch direction is
                        \ negative (in which case we "press" KY5, "X", to
                        \ decrease the pitch, pulling the nose up) or positive
                        \ (in which case we "press" KY6, "S", to increase the
                        \ pitch, pushing the nose down)
 BCS P%+4               \ If the C flag is set, skip the following instruction

 LDX #8                 \ Set X = 8, so we "press" KY+8, i.e. KY6, with the next
                        \ instruction ("S", increase pitch, so the nose dives)

 STA KL,X               \ Store 128 in either KY5 or KY6 to "press" the relevant
                        \ key, depending on whether the pitch direction is
                        \ negative (in which case we "press" KY5, "X", to
                        \ decrease the pitch, pulling the nose up) or positive
                        \ (in which case we "press" KY6, "S", to increase the
                        \ pitch, pushing the nose down)

Flight, 6502SP, Master
 LDA JSTY               \ Fetch A from JSTY so the next instruction has no
                        \ effect

.DK13

 STA JSTY               \ Store A in JSTY to update the current pitch rate

Master
IF _COMPACT

 JMP DK152              \ Jump to DK152 to skip reading the joystick, as this is
                        \ a Master Compact that doesn't support an analogue
                        \ joystick (instead it supports a digital joystick,
                        \ which is read elsewhere)

ENDIF

.DK15

 LDA JSTK               \ If JSTK is zero, then we are configured to use the
 BEQ DK152              \ keyboard rather than the joystick, so jump to DK152 to
                        \ skip reading the joystick

IF _SNG47

 LDA JOPOS              \ Fetch the high byte of the joystick X value

 EOR JSTE               \ The high byte A is now EOR'd with the value in
                        \ location JSTE, which contains &FF if both joystick
                        \ channels are reversed and 0 otherwise (so A now
                        \ contains the high byte but inverted, if that's what
                        \ the current settings say)

 ORA #1                 \ Ensure the value is at least 1

 STA JSTX               \ Store the resulting joystick X value in JSTX

 LDA JOPOS+1            \ Fetch the high byte of the joystick Y value

 EOR #&FF               \ This EOR is used in conjunction with the EOR JSTGY
                        \ below, as having a value of 0 in JSTGY means we have
                        \ to invert the joystick Y value, and this EOR does
                        \ that part

 EOR JSTE               \ The high byte A is now EOR'd with the value in
                        \ location JSTE, which contains &FF if both joystick
                        \ channels are reversed and 0 otherwise (so A now
                        \ contains the high byte but inverted, if that's what
                        \ the current settings say)

 EOR JSTGY              \ JSTGY will be 0 if the game is configured to reverse
                        \ the joystick Y channel, so this EOR along with the
                        \ EOR #&FF above does exactly that

 STA JSTY               \ Store the resulting joystick Y value in JSTY

 LDA VIA+&40            \ Read 6522 System VIA input register IRB (SHEILA &40)

 AND #%00010000         \ Bit 4 of IRB (PB4) is clear if joystick 1's fire
                        \ button is pressed, otherwise it is set, so AND'ing
                        \ the value of IRB with %10000 extracts this bit

 BNE DK4                \ If the joystick fire button is not being pressed,
                        \ jump to DK4 to scan for other keys

 LDA #&FF               \ Update the key logger at KY7 to "press" the "A" (fire)
 STA KY7                \ button

 BNE DK4                \ Jump to DK4 to scan for other keys (this BNE is
                        \ effectively a JMP as A is never 0)

ELIF _COMPACT

 JSR RDJOY              \ Call RDJOY to read from either the analogue or digital
                        \ joystick

 BCC DK4                \ If we just read from the analogue joystick, the C flag
                        \ will be clear, so jump to DK4 to scan for other keys

                        \ Otherwise we just read the digital joystick, so we now
                        \ update the pitch and roll

ENDIF

Flight, 6502SP
Master
.DK15
.DK152

Cassette, Flight, 6502SP, Electron
Master
 LDX JSTX               \ Set X = JSTX, the current roll rate (as shown in the
                        \ RL indicator on the dashboard)

 LDA #7                 \ Set A to 7, which is the amount we want to alter the
                        \ roll rate by if the roll keys are being pressed

 LDY KL+3               \ If the "<" key is being pressed, then call the BUMP2
 BEQ P%+5               \ routine to increase the roll rate in X by A
 JSR BUMP2

 LDY KL+4               \ If the ">" key is being pressed, then call the REDU2
 BEQ P%+5               \ routine to decrease the roll rate in X by A, taking
 JSR REDU2              \ the keyboard auto re-centre setting into account

 STX JSTX               \ Store the updated roll rate in JSTX

 ASL A                  \ Double the value of A, to 14

 LDX JSTY               \ Set X = JSTY, the current pitch rate (as shown in the
                        \ DC indicator on the dashboard)

 LDY KL+5               \ If the "X" key is being pressed, then call the REDU2
 BEQ P%+5               \ routine to decrease the pitch rate in X by A, taking
 JSR REDU2              \ the keyboard auto re-centre setting into account

 LDY KL+6               \ If the "S" key is being pressed, then call the BUMP2
 BEQ P%+5               \ routine to increase the pitch rate in X by A
 JSR BUMP2

 STX JSTY               \ Store the updated roll rate in JSTY
 LDX JSTX               \ Set X = JSTX, the current roll rate (as shown in the
                        \ RL indicator on the dashboard)

 LDA #7                 \ Set A to 7, which is the amount we want to alter the
                        \ roll rate by if the roll keys are being pressed

 LDY KY3                \ If the "<" key is not being pressed, skip the next
 BEQ P%+5               \ instruction

 JSR BUMP2              \ The "<" key is being pressed, so call the BUMP2
                        \ routine to increase the roll rate in X by A

 LDY KY4                \ If the ">" key is not being pressed, skip the next
 BEQ P%+5               \ instruction

 JSR REDU2              \ The "<" key is being pressed, so call the REDU2
                        \ routine to decrease the roll rate in X by A, taking
                        \ the keyboard auto re-centre setting into account

 STX JSTX               \ Store the updated roll rate in JSTX

 ASL A                  \ Double the value of A, to 14

 LDX JSTY               \ Set X = JSTY, the current pitch rate (as shown in the
                        \ DC indicator on the dashboard)

 LDY KY5                \ If the "X" key is not being pressed, skip the next
 BEQ P%+5               \ instruction

 JSR REDU2              \ The "X" key is being pressed, so call the REDU2
                        \ routine to decrease the pitch rate in X by A, taking
                        \ the keyboard auto re-centre setting into account

 LDY KY6                \ If the "S" key is not being pressed, skip the next
 BEQ P%+5               \ instruction

 JSR BUMP2              \ The "S" key is being pressed, so call the BUMP2
                        \ routine to increase the pitch rate in X by A

 STX JSTY               \ Store the updated roll rate in JSTY