****************************************************************************** * * * 6805R3 KEYBOARD ENCODER * * * * Modified from 6805U2 keyboard encoder. * * * * Features: * * * * Full ASCII parallel output * * 7 bits, generates all 128 codes * * Full ASCII serial output * * 7 bits, generates all 128 codes * * Control keys on separate keys: * * shift,control,repeat,alpha lock * * Low parts count: * * MC6805R3, 1 capacitor, (12 pullup resistors) * * Negative edge keyboard strobe * * 2-Key rollover (N-key rollover with diodes) * * Easy P.C. board layout * * Single 5 Volt supply operation * * * ****************************************************************************** * * Important constants * NKEYS equ 64 using an 8 by 8 matrix row equ portb keyboard row driver port column equ portd keyboard column inputs data equ porta encoder parallel output data lines strobe equ 7 porta bit7 = strobe junk equ portc multiple use I/O port * * Bits of junk I/O port C * ctrl equ 7 control key funct equ 6 function: `1' selects keyboard encoder serout equ 5 serial output bit shift equ 4 shift key repeat equ 3 repeat key lock equ 2 alpha lock (upper case only) * baud rate select by bits `1' &`0' * * C1 C0 * 0 0 300 baud * 0 1 1200 baud * 1 0 4800 baud * 1 1 9600 baud * * Character constants * BS equ $08 backspace (ctrl-H) TAB equ $09 tab (ctrl-I) ESC equ $1B escape character (ctrl-[) CAN equ $18 cancel (ctrl-X) SP equ BL ascii blank RUB equ $7F rubout BREAK equ $FE break key code NOKEY equ $FF invalid key code STOP equ $13 (ctrl s) GO equ $11 (ctrl q) * * RAM variables * damper equ RAM count register for debounce delay coltmp equ RAM+1 saved column mask * * kbd --- 6805 keyboard encoder * kbd * * Setup I/O port (port a ) * clr data initialize data outputs lda #$80 set strobe=1 sta data . lda #$FF . sta data+ddr turn on data outputs (initially zero) * * initialize keyboard matrix ports ( ports b & d ) * sta row next do the row drivers sta row+ddr all ones to begin with clr column+ddr establish kbd column input * clr junk+ddr init option port lda #$20 serout ddr sta junk . sta junk+ddr . * ldx #NKEYS-1 make it look like a scan just finished clra bra next skip to next key test * * Main loop, check for any key down * scan_loop bit column this key down? bne next no, try next one bsr debounce see if it was a fluke bsr debounce more delay (total is about 5ms) bit column check it again bne next was just noise bsr output the real thing, send it out next incx move index lsra move mask to next row bne scan_loop still more keys in this row lda #%10000000 reinitialize row mask sec shift the zero to the next row ror row cmpx #NKEYS have we checked all keys? bne scan_loop no, more keys this time around ldx #$7F move zero to first row again stx row clrx reset key index bra scan_loop continue scanning * * debounce --- Delay while keyboard bounces (approx 2.5ms) * debounce clr damper deb2 inc damper bne deb2 rts * * output --- Send current key out on port A * * Key code to output is in X. A has the current column * that the key was found on. Output will return with A and * X unchanged so that the main loop can continue scanning * where it left off. This is the 2-key rollover * algorithm. The serial output routine is in the monitor. * output sta coltmp save current column * * Interpret key code as per ASCII tables * lda down,x pickup unshifted character cmp #BREAK break key ? bne arnbk no,continue bclr serout,junk set ser line =`0' jsr delay250 wait 250 ms wtbrk lda coltmp restore last column checked bit column wait till key is lifted beq wtbrk . bset serout,junk . rts & exit arnbk brset shift,junk,okdown check shift key lda up,x pickup shifted character okdown cmp #NOKEY invalid key combination? bne doit will output some character lda coltmp restore column last checked nkd bit column still down? beq nkd wait rts * * check if alpha lock is on * doit brset lock,junk,nomap clear means map lower to upper cmp #'a is character between a and z? blo nomap cmp #'z bhi nomap sub #$20 map to upper case * * check if control key is pressed * nomap brset ctrl,junk,sendit cmp #'@ control codes only valid for `sticks' 4-7 blo sendit can't control this character and #$1F clear high order bits and make it a control sendit ora #$80 set msb for strobe sta data update the data lines bclr strobe,data signal new data valid and #$7f clear strobe bit jsr putc send char serially waitup brset repeat,junk,norpt bsr delay25 25ms delay bset strobe,data reset strobe bsr delay25 25ms delay bclr strobe,data returns low lda data restore char and #$7f clear msb jsr putc send serially agian norpt lda coltmp restore column mask bit column is the key still down? beq waitup yes, check other stuff again bset strobe,data signal key going up (data still valid) rts wazu * * delay routines * * delay250 --- 250 ms delay delay250 lda #100 bra d50more * delay25 --- 25ms delay delay25 lda #10 20*2.5=50 d50more bsr debounce delay 2.5ms deca bne d50more rts * * * Keyboard encoder mapping tables. Converts the matrix * position of the key to whatever you like. In this case, * the mapping is to good ol' ASCII. * * down --- The unshifted characters down fcb TAB, '1, '2, '3, '4, '5, '6, '7 fcb ESC, 'q, 'w, 'e, 'r, 't, 'y, 'u fcb CAN, 'a, 's, 'd, 'f, 'g, 'h, 'j fcb SP, 'z, 'x, 'c, 'v, 'b, 'n, 'm fcb '8, '9, '0, '-, '^, '\, '_, STOP fcb 'i, 'o, 'p, '@, '[, '], BS, GO fcb 'k, 'l, ';, ':, RUB, CR, NOKEY, NOKEY fcb ',, '., '/, SP, NOKEY, LF, NOKEY, BREAK * * up --- The corresponding shifted characters up fcb TAB, '!, '", '#, '$, '%, '&, '' fcb ESC, 'Q, 'W, 'E, 'R, 'T, 'Y, 'U fcb CAN, 'A, 'S, 'D, 'F, 'G, 'H, 'J fcb SP, 'Z, 'X, 'C, 'V, 'B, 'N, 'M fcb '(, '), '0, '=, '~, '|, RUB, STOP fcb 'I, 'O, 'P, '`, '{, '}, BS, GO fcb 'K, 'L, '+, '*, RUB, CR, NOKEY, NOKEY fcb '<, '>, '?, SP, NOKEY, LF, NOKEY, BREAK * * end of keyboard encoder * ******************************************************************************