TI Little Professor (1976)

Chip labeled 
TMS0975NL
ZA0356
CSP 7810

chip bottom
GP0975CS
SINGAPORE

die labeled
0970D-75C

16 buttons: 0-9, Set, Go, +, -, *, /
9 7-segment LEDs ##+##=###
1 switch - Level 1 2 3 4

digit 4 is just = (segments A and G)

           \./
digit 7 is --- for +, - x, ÷
           /.\
           
   /       \ /   .
 ---  ---       ---
 /         / \   .
 
 digit 7 segments
 
 G A B
   F
 E D C
 
TMS0970 pinout
Pin 1 -  Digit 7
Pin 2 -  Digit 8
Pin 3 -  Digit 9 (leftmost)
Pin 4 -  9V battery negative
Pin 5 -  keypad column 0 + level switch 1
Pin 6 -  keypad column 1 + level switch 2
Pin 7 -  keypad column 2 + level switch 3
Pin 8 -  keypad column 3 + level switch 4
Pin 9 -  N/C
Pin 10 - level switch common
Pin 11 - Segment G
Pin 12 - Segment F
Pin 13 - Segment E + keypad row 4
Pin 14 - N/C
Pin 15 - Segment D + keypad row 3
Pin 16 - Segment C + keypad row 2
Pin 17 - Segment B + keypad row 1
Pin 18 - Segment A
Pin 19 - N/C
Pin 20 - 9v battery positive (via on/off switch)
Pin 21 - Digit 1 (rightmost)
Pin 22 - N/C
Pin 23 - N/C
Pin 24 - Digit 2
Pin 25 - Digit 3
Pin 26 - Digit 4
Pin 27 - Digit 5
Pin 28 - Digit 6


Key Matrix
--------------------------------------
         Pin 5   Pin 6   Pin 7   Pin 8
Pin 13      7       8      9       /
Pin 15      4       5      6       X
Pin 16      1       2      3       -
Pin 17     Set      0      Go      +