The TI1270 calculator uses a TMS0970.

chip top marked TMC0974NL ZA0355 AP 7640
chip bottom marked DP0974A SINGAPORE
die labeled 0970D-74A

8 7-segment LEDs
24 pushbuttons - 0-9, Clear, decimal point, =, +, -, X, /
store, recall, pi, reciprocal, square, square root, change sign.

TI1270 keypad layout
--------------------
        K1      K2      K4      K8
Seg DP  1/x     x^2     sqrt    +/-
Seg F   STO     RCL     PI      /
Seg E   7       8       9       X
Seg D   4       5       6       -
Seg C   1       2       3       +
Seg B   CE/C    0       .       =

pinout
------
1  digit 7
2  digit 8
3  N/C
4  9v battery negative
5  KP column 0
6  KP column 1
7  KP column 2
8  KP column 3
9  N/C
10 Segment DP / KP row 5
11 Segment G 
12 Segment F  / KP row 4
13 Segment E  / KP row 3
14 Segment D  / KP row 2
15 Segment C  / KP row 1
16 Segment B  / KP row 0
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

Output O PLA
------------
11111110 0
10110000 1
11101101 2
11111001 3
10110011 4
11011011 5
11011111 6
11110000 7
11111111 8
11111011 9
00000000  
00000000  
00000000  
01000010 r
00000001 -
00000000