TI-1000

Chip labeled 
TMC1991NL
ATP 7736

die labeled
1991-91A

20 buttons: 0-9, ., On, Off,  +, -, *, /, =, +/-, %
8 7-segment LEDs

 pinout
1  digit 4
2  digit 5
3  digit 6
4  digit 7
5  digit 8
6  row 1
7  N/C
8  col 1
9  row 2
10 col 2
11 row 3
12 col 3
13 row 4
14 col 4
15 row 5
16 9v batt -
17 9v batt +
18 seg B
19 seg A
20 seg G
21 seg F
22 seg E
23 seg D
24 seg C
25 seg DP
26 digit 1
27 digit 2
28 digit 3


Key Matrix

      8    10    12     14
 
15   OFF   +/-    %      /
13    7     8     9      *
11    4     5     6      -
 9    1     2     3      +
 6   ON     0     .      =