Version analysis of KTRAN - Elite on the 6502

This code appears in the following versions (click to see it in the source code):

6502 Second Processor and Master

Code variations between these versions are shown below.

       Name: KTRAN
       Type: Variable
   Category: Keyboard

Code variation 1 of 1A variation in the comments only

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Master
6502SP
    Summary: An unused key logger buffer that's left over from the 6502 Second
             Processor version of Elite
    Summary: The key logger buffer that gets updated by the OSWORD 240 command


 KTRAN is a buffer that is filled with key logger information by the KEYBOARD
 routine in the I/O processor, which is run when the parasite sends an OSWORD
 &F0 command to the I/O processor. The buffer contains details of keys being
 pressed, with KTRAN being filled with bytes #2 to #14 from the KEYBOARD
 routine (because KEYBOARD is called with OSSC pointing to buf, and buf is
 equal to KTRAN - 2).

 The key logger buffer is filled as follows:

   KTRAN + 0           Internal key number of any non-primary flight control
                       key that is being pressed

   KTRAN + 1           "?" is being pressed (0 = no, &FF = yes)

   KTRAN + 2           Space is being pressed (0 = no, &FF = yes)

   KTRAN + 3           "<" is being pressed (0 = no, &FF = yes)

   KTRAN + 4           ">" is being pressed (0 = no, &FF = yes)

   KTRAN + 5           "X" is being pressed (0 = no, &FF = yes)

   KTRAN + 6           "S" is being pressed (0 = no, &FF = yes)

   KTRAN + 7           "A" is being pressed (0 = no, &FF = yes)

   KTRAN + 8           Joystick X value (high byte)

   KTRAN + 9           Joystick Y value (high byte)

   KTRAN + 10          Bitstik rotation value (high byte)

   KTRAN + 12          Joystick 1 fire button is being pressed (Bit 4 set = no,
                       Bit 4 clear = yes)


 Other entry points:

   buf                  The two OSWORD size bytes for transmitting the key
                        logger from the I/O processor to the parasite



.buf

 EQUB 2                 \ Transmit 2 bytes as part of this command

 EQUB 15                \ Receive 15 bytes as part of this command

.KTRAN

 EQUS "1234567890"      \ A 17-byte buffer to hold the key logger data from the
 EQUS "1234567"         \ KEYBOARD routine in the I/O processor (note that only
                        \ 12 of these bytes are actually updated by the KEYBOARD
                        \ routine)