module  BCD7
title 'seven segment display decoder    1 Aug 1990
Walter Bright  Data I/O Corp  Redmond WA'
"          a       
"         ---       BCD-to-seven-segment decoder similar to the 7449
"       f| g |b
"         ---           segment identification
"       e| d |c
"         ---
        bcd7 device  'P16P8';

        D3,D2,D1,D0     pin 2,3,4,5;
        a,b,c,d,e,f,g   pin 13,14,15,16,17,18,19 istype 'com';

        bcd     = [D3,D2,D1,D0];
        led     = [a,b,c,d,e,f,g];

        ON,OFF  = 0,1;                  " for common anode LEDs 
        L,H,X,Z = 0,1,.X.,.Z.;
@dcset
truth_table (bcd -> [ a ,  b ,  c ,  d ,  e ,  f ,  g ])
              0  -> [ ON,  ON,  ON,  ON,  ON,  ON, OFF];
              1  -> [OFF,  ON,  ON, OFF, OFF, OFF, OFF];
              2  -> [ ON,  ON, OFF,  ON,  ON, OFF,  ON];
              3  -> [ ON,  ON,  ON,  ON, OFF, OFF,  ON];
              4  -> [OFF,  ON,  ON, OFF, OFF,  ON,  ON];
              5  -> [ ON, OFF,  ON,  ON, OFF,  ON,  ON];
              6  -> [ ON, OFF,  ON,  ON,  ON,  ON,  ON];
              7  -> [ ON,  ON,  ON, OFF, OFF, OFF, OFF];
              8  -> [ ON,  ON,  ON,  ON,  ON,  ON,  ON];
              9  -> [ ON,  ON,  ON,  ON, OFF,  ON,  ON];

test_vectors (bcd -> [ a ,  b ,  c ,  d ,  e ,  f ,  g ])
               0  -> [ ON,  ON,  ON,  ON,  ON,  ON, OFF];
               1  -> [OFF,  ON,  ON, OFF, OFF, OFF, OFF];
               2  -> [ ON,  ON, OFF,  ON,  ON, OFF,  ON];
               3  -> [ ON,  ON,  ON,  ON, OFF, OFF,  ON];
               4  -> [OFF,  ON,  ON, OFF, OFF,  ON,  ON];
               5  -> [ ON, OFF,  ON,  ON, OFF,  ON,  ON];
               6  -> [ ON, OFF,  ON,  ON,  ON,  ON,  ON];
               7  -> [ ON,  ON,  ON, OFF, OFF, OFF, OFF];
               8  -> [ ON,  ON,  ON,  ON,  ON,  ON,  ON];
               9  -> [ ON,  ON,  ON,  ON, OFF,  ON,  ON];
              10  -> [ X ,  X ,  X ,  X ,  X ,  X ,  X ];
              11  -> [ X ,  X ,  X ,  X ,  X ,  X ,  X ];
              12  -> [ X ,  X ,  X ,  X ,  X ,  X ,  X ];
              13  -> [ X ,  X ,  X ,  X ,  X ,  X ,  X ];
              14  -> [ X ,  X ,  X ,  X ,  X ,  X ,  X ];
              15  -> [ X ,  X ,  X ,  X ,  X ,  X ,  X ];
end