;/******************************************************************************/
;/  PC Keyboard decoder                                             /
;/                                                            /
;/  Designed and written by Daryl Rictor (c)2004                        /
;/******************************************************************************/
;
; All standard keys and control keys are decoded to 7 bit (bit 7=0) standard ASCII.
; Control key note: It is being assumed that if you hold down the ctrl key,
; you are going to press an alpha key (A-Z) with it (except break key defined below.)
; If you press another key, its ascii code's lower 5 bits will be send as a control
; code.  For example, Ctrl-1 sends $11, Ctrl-; sends $2B (Esc), Ctrl-F1 sends $01.
;
; The following non-standard keys are decoded with bit 7=1, bit 6=0 if not shifted,
; bit 6=1 if shifted, and bits 0-5 identify the key.
;
; Function key translation: 
;              ASCII / Shifted ASCII
;            F1 - 81 / C1
;            F2 - 82 / C2
;            F3 - 83 / C3
;            F4 - 84 / C4
;            F5 - 85 / C5
;            F6 - 86 / C6
;            F7 - 87 / C7
;            F8 - 88 / C8
;            F9 - 89 / C9
;           F10 - 8A / CA
;           F11 - 8B / CB
;           F12 - 8C / CC
;
; The Print screen and Pause/Break keys are decoded as:
;                ASCII  Shifted ASCII
;    Ctrl-Break - 02       02  (Ctrl-B) (can be changed to AE/EE)(non-repeating key) 
;     Pause/Brk - 03       03  (Ctrl-C) (can change to 8E/CE)(non-repeating key)
;      Scrl Lck - 8D       CD 
;        PrtScn - 8F       CF
;
; The Alt key is decoded as a hold down (like shift and ctrl) but does not
; alter the ASCII code of the key(s) that follow.  Rather, it sends
; a Alt key-down code and a seperate Alt key-up code.  The user program
; will have to keep track of it if they want to use Alt keys.
;
;      Alt down - A0
;        Alt up - E0
;
; Example byte stream of the Alt-F1 sequence:  A0 81 E0.  If Alt is held down longer
; than the repeat delay, a series of A0's will preceeed the 81 E0.
; i.e. A0 A0 A0 A0 A0 A0 81 E0.
;
; The special windows keys are decoded as follows:
;                           ASCII    Shifted ASCII
;        Left Menu Key -      A1          E1
;       Right Menu Key -      A2          E2
;     Right option Key -      A3          E3
;            Power Key -      A4          E4 
;            Sleep Key -      A5          E5
;             Wake Key -      A6          E6
;
;
; The following "cursor" keys ignore the shift key and return their special key code
; when numlock is off or their direct labeled key is pressed.  When numlock is on, the digits
; are returned reguardless of shift key state.       
; keypad(NumLck off) or Direct - ASCII    Keypad(NumLck on) ASCII
;          Keypad 0        Ins - 90                 30
;          Keypad .        Del - 7F                 2E
;          Keypad 7       Home - 97                 37
;          Keypad 1        End - 91                 31
;          Keypad 9       PgUp - 99                 39
;          Keypad 3       PgDn - 93                 33
;          Keypad 8    UpArrow - 98                 38
;          Keypad 2    DnArrow - 92                 32
;          Keypad 4    LfArrow - 94                 34
;          Keypad 6    RtArrow - 96                 36
;          Keypad 5    (blank) - 95                 35
;