Electronic Detective

chip top marked TMS0980NLL MP6100A DBT 8014 SINGAPORE
die labeled 0980B-00

7 7-segment LEDs (2 - 3 - 2)
5x8 keypad (only 17 buttons used)

                        keypad layout
-------------------------------------------------------
          Pin 20  Pin 17   Pin 14  Pin 18   Pin 12 
Pin 10      ON    unused     7       4        1
          unused  unused   unused  unused   unused
Pin 6       OFF   unused     8       5        2
          unused  unused   unused  unused   unused
Pin 8     unused    0        9       6        3
          unused  unused   unused  unused   unused
          unused  unused   unused  unused   unused
Pin 7    end turn enter   I accuse private  suspect
                                  question
                                  
Pin 1  - Digit 5
Pin 2  - Digit 6
Pin 3  - Digit 7
Pin 4  - N/C
Pin 5  - 9V battery - / Speaker 1
Pin 6  - Keypad Row 6
Pin 7  - Keypad Row 1
Pin 8  - Keypad Row 4
Pin 9  - N/C
Pin 10 - Keypad Row 8
Pin 11 - N/C
Pin 12 - Keypad Column 5 / Segment B
Pin 13 - Segment G
Pin 14 - Keypad Column 3 / Segment D
Pin 15 - Segment A
Pin 16 - Segment F
Pin 17 - Keypad Column 2 / Segment E
Pin 18 - Keypad Column 4 / Segment C
Pin 19 - N/C
Pin 20 - 9V battery + / Keypad Column 1
Pin 21 - N/C
Pin 22 - N/C
Pin 23 - Pin 24 / Speaker 2
Pin 24 - Pin 23 / Speaker 2
Pin 25 - Digit 1
Pin 26 - Digit 2
Pin 27 - Digit 3
Pin 28 - Digit 4

Output O PLA
11101110 0
10001000 1
11100011 2
11001011 3
10001101 4
01001111 5
01101101 6
10001010 7
11101111 8
10001111 9
10101110 =
00000000  
01100110 C
11101001 d
01100111 E
00100111 F