The TI1250 calculator uses a TMS0970.

chip top marked TMS0972NL ZA0348 AP 7615
chip bottom marked JP0972A SINGAPORE
die labeled 0970D-72A

9 7-segment LEDs (leftmost is just negative sign)
24 pushbuttons - 0-9, clear, decimal point, =, +, -, X, /, %,
clear entry, store, recall, memory minus, memory plus, change sign.

TI1250 keypad layout
--------------------
        K1      K2      K4      K8
Seg DP  MC      MR      M-      M+
Seg F   C       CS      %       /
Seg E   7       8       9       X
Seg D   4       5       6       -
Seg C   1       2       3       +
Seg B   CE      0       .       =

pinout
------
1  digit 7
2  digit 8
3  digit 9 (leftmost, just segment G)
4  9v battery negative
5  KP column 1 (left)
6  KP column 2
7  KP column 3
8  KP column 4 (right)
9  N/C
10 Segment DP / KP row 6
11 Segment G 
12 Segment F  / KP row 5
13 Segment E  / KP row 4
14 Segment D  / KP row 3
15 Segment C  / KP row 2
16 Segment B  / KP row 1
17 Segment A
18 connected to pin 19
19 connected to pin 18
20 +9v through switch
21 N/C
22 N/C
23 digit 1
24 digit 2
25 digit 3
26 digit 4
27 digit 5
28 digit 6

0/0 flashes the display 4.4 times per second