Jupiter Ace keyboard layout
                      ===========================

                            Key Characters
    +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
    |DELLN|CAPS |     | INV |LEFT |DOWN | UP  |RIGHT|GRAPH| DEL |
    |  !  |  @  |  #  |  $  |  %  |  &  |  '  |  (  |  )  |  _  |
    |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  |  0  |
    +-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+
      |  Q  |  W  |  E  |  R  |  T  |  Y  |  U  |  I  |  O  |  P  |
      |     |     |     |  <  |  >  |  [  |  ]  | (C) |  ;  |  "  |
      |  q  |  w  |  e  |  r  |  t  |  y  |  u  |  i  |  o  |  p  |
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         |  A  |  S  |  D  |  F  |  G  |  H  |  J  |  K  |  L  |ENTER|
         |  ~  |  |  |  \  |  {  |  }  |  ^  |  -  |  +  |  =  |ENTER|
         |  a  |  s  |  d  |  f  |  g  |  h  |  j  |  k  |  l  |ENTER|
    +----+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+-----+
    | SHIFT  |  Z  |  X  |  C  |  V  |  B  |  N  |  M  | EXT | BREAK |
    |  EXT   |  :  |  £  |  ?  |  /  |  *  |  ,  |  .  | SYM | SPACE |
    | SHIFT  |  z  |  x  |  c  |  v  |  b  |  n  |  m  | SYM | SPACE |
    +--------+-----+-----+-----+-----+-----+-----+-----+-----+-------+

                            Character Codes
    +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
    | &0A | &02 |  3  | &08 | &01 | &07 | &09 | &03 | &04 | &05 |
    |  !  |  @  |  #  |  $  |  %  |  &  |  '  |  (  |  )  |  _  |
    |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  |  0  |
    +-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+
      |  Q  |  W  |  E  |  R  |  T  |  Y  |  U  |  I  |  O  |  P  |
      |  Q  |  W  |  E  |  <  |  >  |  [  |  ]  | &7F |  ;  |  "  |
      |  q  |  w  |  e  |  r  |  t  |  y  |  u  |  i  |  o  |  p  |
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         |  A  |  S  |  D  |  F  |  G  |  H  |  J  |  K  |  L  | &0D |
         |  ~  |  |  |  \  |  {  |  }  |  ^  |  -  |  +  |  =  | &0D |
         |  a  |  s  |  d  |  f  |  g  |  h  |  j  |  k  |  l  | &0D |
    +----+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+---+-+-----+
    | SHIFT  |  Z  |  X  |  C  |  V  |  B  |  N  |  M  | &00 | BREAK |
    |  &00   |  :  |  £  |  ?  |  /  |  *  |  ,  |  .  | SYM |  &20  |
    | SHIFT  |  z  |  x  |  c  |  v  |  b  |  n  |  m  | SYM |  &20  |
    +--------+-----+-----+-----+-----+-----+-----+-----+-----+-------+
Notes:     Top line: Shift+key
        Middle line: Symbol+key
        Bottom line: unshifted key

                         Keyboard internal key codes
        +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
 A11--  | &24 | &1C | &14 | &0C | &04 | &03 | &0B | &13 | &1B | &23 |   --A12
        |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  |  0  |
        +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
 A10--  | &25 | &1D | &15 | &0D | &05 | &02 | &0A | &12 | &1A | &22 |   --A13
        |  Q  |  W  |  E  |  R  |  T  |  Y  |  U  |  I  |  O  |  P  |
        +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
 A9--   | &26 | &1E | &16 | &0E | &06 | &01 | &09 | &11 | &19 | &21 |   --A14
        |  A  |  S  |  D  |  F  |  G  |  H  |  J  |  K  |  L  |ENTER|
      +-+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-+
 A8-- |  &27  | &1F | &17 | &0F | &07 | &00 | &08 | &10 | &18 |  &20  | --A15
      | SHIFT | SYM |  Z  |  X  |  C  |  V  |  B  |  N  |  M  | SPACE |
      +-------+-----+-----+-----+-----+-----+-----+-----+-----+-------+
          |      |     |     |     |     |     |     |     |      |
          D0     D1    D2    D3    D4    D4    D3    D2    D1     D0

While the Jupiter Ace uses the same type of keyboard matrix as the ZX Spectrum,
the SYMBOL key is in the same data row as the SHIFT key. This makes for easier
keyboard scanning as both SHIFT and SYMBOL are the final keys to be tested, so
pressing one of them on their own does not block a scan of an earlier key.