-- 
  -- The ROM below maps scan codes to 7-bit ASCII codes. To index this
  -- array, concatenate the CTRL state (1 = CTRL key currently down)
  -- and the SHIFT state (1 = SHIFT key currently down) with the scan
  -- code as shown below:
  -- +------+-------+-----+-----+-----+-----+-----+-----+-----+-----+
  -- | CTRL | SHIFT |                8-bit SCAN CODE                |
  -- +------+-------+-----+-----+-----+-----+-----+-----+-----+-----+
  -- Unused codes are mapped to 127 (7F). The array does not support the
  -- keys on the keypad (which use extended scan codes).
  type map_type is array (0 to 1023) of integer range 0 to 127;
  
  constant scan2ascii: map_type :=
  ( -- NUMBER KEYS
    16#045#=>48,  16#145#=>41,               -- 0)
    16#016#=>49,  16#116#=>33,               -- 1!
    16#01E#=>50,  16#11E#=>64,  16#31E#=>0,  -- 2@ CTRL+@
    16#026#=>51,  16#126#=>35,               -- 3#
    16#025#=>52,  16#125#=>36,               -- 4$
    16#02E#=>53,  16#12E#=>37,               -- 5%
    16#036#=>54,  16#136#=>94,  16#336#=>30, -- 6^ CTRL+^
    16#03D#=>55,  16#13D#=>38,               -- 7&
    16#03E#=>56,  16#13E#=>42,               -- 8*
    16#046#=>57,  16#146#=>40,               -- 9(
  
    -- ALPHABETIC KEYS
    16#01C#=>97,  16#11C#=>65,  16#21C#=>1,  -- aA
    16#032#=>98,  16#132#=>66,  16#232#=>2,  -- bB
    16#021#=>99,  16#121#=>67,  16#221#=>3,  -- cC
    16#023#=>100, 16#123#=>68,  16#223#=>4,  -- dD
    16#024#=>101, 16#124#=>69,  16#224#=>5,  -- eE
    16#02B#=>102, 16#12B#=>70,  16#22B#=>6,  -- fF
    16#034#=>103, 16#134#=>71,  16#234#=>7,  -- gG
    16#033#=>104, 16#133#=>72,  16#233#=>8,  -- hH
    16#043#=>105, 16#143#=>73,  16#243#=>9,  -- iI
    16#03B#=>106, 16#13B#=>74,  16#23B#=>10, -- jJ
    16#042#=>107, 16#142#=>75,  16#242#=>11, -- kK
    16#04B#=>108, 16#14B#=>76,  16#24B#=>12, -- lL
    16#03A#=>109, 16#13A#=>77,  16#23A#=>13, -- mM
    16#031#=>110, 16#131#=>78,  16#231#=>14, -- nN
    16#044#=>111, 16#144#=>79,  16#244#=>15, -- oO
    16#04D#=>112, 16#14D#=>80,  16#24D#=>16, -- pP
    16#015#=>113, 16#115#=>81,  16#215#=>17, -- qQ
    16#02D#=>114, 16#12D#=>82,  16#22D#=>18, -- rR
    16#01B#=>115, 16#11B#=>83,  16#21B#=>19, -- sS
    16#02C#=>116, 16#12C#=>84,  16#22C#=>20, -- tT
    16#03C#=>117, 16#13C#=>85,  16#23C#=>21, -- uU
    16#02A#=>118, 16#12A#=>86,  16#22A#=>22, -- vV
    16#01D#=>119, 16#11D#=>87,  16#21D#=>23, -- wW
    16#022#=>120, 16#122#=>88,  16#222#=>24, -- xX
    16#035#=>121, 16#135#=>89,  16#235#=>25, -- yY
    16#01A#=>122, 16#11A#=>90,  16#21A#=>26, -- zZ
    16#054#=>91,  16#154#=>123, 16#254#=>27, -- [{
    16#05D#=>92,  16#15D#=>124, 16#25D#=>28, -- \|
    16#05B#=>93,  16#15B#=>125, 16#25B#=>29, -- ]}
    
    -- OTHER PRINTABLE KEYS
    16#00E#=>96,  16#10E#=>126,              -- `~
    16#04E#=>45,  16#14E#=>95,  16#34E#=>31, -- -_ CTRL+_
    16#055#=>61,  16#155#=>43,               -- =+
    16#04C#=>59,  16#14C#=>58,               -- ;:
    16#052#=>39,  16#152#=>34,               -- '"
    16#041#=>44,  16#141#=>60,               -- ,<
    16#049#=>46,  16#149#=>62,               -- .>
    16#04A#=>47,  16#14A#=>63,               -- /?
    16#029#=>32,  16#129#=>32,  16#229#=>32, -- SPACE
    
    -- CONTROL KEYS
    16#076#=>27,  16#176#=>27,  16#276#=>27, -- ESC
    16#066#=>8,   16#166#=>8,   16#266#=>8,  -- BS
    16#00D#=>9,   16#10D#=>9,   16#20D#=>9,  -- TAB
    16#05A#=>13,  16#15A#=>13,  16#25A#=>13, -- CR
    
    others=>127 );