Version analysis of KYTB - Elite on the BBC Micro

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

Cassette, Disc (flight), 6502 Second Processor, Master and Electron

Code variations between these versions are shown below.

       Name: KYTB
       Type: Variable
   Category: Keyboard
    Summary: Lookup table for in-flight keyboard controls
  Deep dive: The key logger

Code variation 1 of 6A variation in the comments only

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Cassette, Flight, 6502SP
Master
Electron
 Keyboard table for in-flight controls. This table contains the internal key
 codes for the flight keys (see p.142 of the Advanced User Guide for a list of
 internal key numbers).
 Keyboard table for in-flight controls. This table contains the internal key
 codes for the flight keys, EOR'd with &FF to invert each bit.
 Keyboard table for in-flight controls. This table contains the internal key
 codes for the flight keys (see p.40 of the Electron Advanced User Guide for a
 list of internal key numbers).


 The pitch, roll, speed and laser keys (i.e. the seven primary flight
 control keys) have bit 7 set, so they have 128 added to their internal
 values. This doesn't appear to be used anywhere.

Code variation 2 of 6A variation in the comments only

This variation is blank in the Cassette and Master versions.

Flight, 6502SP, Electron
 Note that KYTB actually points to the byte before the start of the table, so
 the offset of the first key value is 1 (i.e. KYTB+1), not 0.

 Other entry points:

   KYTB                 Contains an RTS

Code variation 3 of 6A variation in the labels only

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Cassette
Flight, 6502SP, Master, Electron
KYTB = P% - 1           \ Point KYTB to the byte before the start of the table
.KYTB

Code variation 4 of 6A variation in the labels only

This variation is blank in the Cassette and Master versions.

Flight, 6502SP, Electron
 RTS                    \ Return from the subroutine (used as an entry point and
                        \ a fall-through from above)

Code variation 5 of 6Related to the Master version

The Master has a very different set of internal key numbers to the BBC Micro and Electron, so the keyboard lookup table for the Master is also very different; the Electron and BBC Micro are much more similar, but the Electron has no TAB key, so "-" launches an energy bomb instead.

Tap on a version to expand it, and tap it again to show to all variations.

Cassette, Flight, 6502SP
Master
Electron
                        \ These are the primary flight controls (pitch, roll,
                        \ speed and lasers):

 EQUB &68 + 128         \ ?         KYTB+1      Slow down
 EQUB &62 + 128         \ Space     KYTB+2      Speed up
 EQUB &66 + 128         \ <         KYTB+3      Roll left
 EQUB &67 + 128         \ >         KYTB+4      Roll right
 EQUB &42 + 128         \ X         KYTB+5      Pitch up
 EQUB &51 + 128         \ S         KYTB+6      Pitch down
 EQUB &41 + 128         \ A         KYTB+7      Fire lasers

                        \ These are the secondary flight controls:

 EQUB &60               \ TAB       KYTB+8      Energy bomb
 EQUB &70               \ ESCAPE    KYTB+9      Launch escape pod
 EQUB &23               \ T         KYTB+10     Arm missile
 EQUB &35               \ U         KYTB+11     Unarm missile
 EQUB &65               \ M         KYTB+12     Fire missile
 EQUB &22               \ E         KYTB+13     E.C.M.
 EQUB &45               \ J         KYTB+14     In-system jump
 EQUB &52               \ C         KYTB+15     Docking computer
 EQUB &DD EOR &FF       \ E         KYTB+0    KY13     E.C.M.
 EQUB &DC EOR &FF       \ T         KYTB+1    KY10     Arm missile
 EQUB &CA EOR &FF       \ U         KYTB+2    KY11     Unarm missile
 EQUB &C8 EOR &FF       \ P         KYTB+3    KY16     Cancel docking computer
 EQUB &BE EOR &FF       \ A         KYTB+4    KY7      Fire lasers
 EQUB &BD EOR &FF       \ X         KYTB+5    KY5      Pitch up
 EQUB &BA EOR &FF       \ J         KYTB+6    KY14     In-system jump
 EQUB &AE EOR &FF       \ S         KYTB+7    KY6      Pitch down
 EQUB &AD EOR &FF       \ C         KYTB+8    KY15     Docking computer
 EQUB &9F EOR &FF       \ TAB       KYTB+9    KY8      Energy bomb
 EQUB &9D EOR &FF       \ Space     KYTB+10   KY2      Speed up
 EQUB &9A EOR &FF       \ M         KYTB+11   KY12     Fire missile
 EQUB &99 EOR &FF       \ <         KYTB+12   KY3      Roll left
 EQUB &98 EOR &FF       \ >         KYTB+13   KY4      Roll right
 EQUB &97 EOR &FF       \ ?         KYTB+14   KY1      Slow down
 EQUB &8F EOR &FF       \ ESCAPE    KYTB+15   KY9      Launch escape pod

 EQUB &F0               \ This value just has to be higher than &80 to act as a
                        \ terminator for the KYTB matching process in DKS1
                        \ These are the primary flight controls (pitch, roll,
                        \ speed and lasers):

 EQUB &68 + 128         \ ?         KYTB+1      Slow down
 EQUB &62 + 128         \ Space     KYTB+2      Speed up
 EQUB &66 + 128         \ <         KYTB+3      Roll left
 EQUB &67 + 128         \ >         KYTB+4      Roll right
 EQUB &42 + 128         \ X         KYTB+5      Pitch up
 EQUB &51 + 128         \ S         KYTB+6      Pitch down
 EQUB &41 + 128         \ A         KYTB+7      Fire lasers

                        \ These are the secondary flight controls:

 EQUB &17               \ -         KYTB+8      Energy bomb
 EQUB &70               \ ESCAPE    KYTB+9      Launch escape pod
 EQUB &23               \ T         KYTB+10     Arm missile
 EQUB &35               \ U         KYTB+11     Unarm missile
 EQUB &65               \ M         KYTB+12     Fire missile
 EQUB &22               \ E         KYTB+13     E.C.M.
 EQUB &45               \ J         KYTB+14     In-system jump
 EQUB &52               \ C         KYTB+15     Docking computer

Code variation 6 of 6Related to an enhanced feature

The lookup table for in-flight keyboard controls contains an extra entry in the enhanced versions, for "P" (cancel docking computer).

This variation is blank in the Cassette, Master and Electron versions.

Flight, 6502SP
 EQUB &37               \ P         KYTB+16     Cancel docking computer