Texas Instruments TMS0972 ASP


With the TMS0952 Texas Instruments introduced in the year 1975 the first "real" single-chip calculator design. Read more about the associated TMS1000 family here. In opposite to the TMS0102 with the discrete segment- and digit-drivers or the TMS0803 with the external digit-drivers this design controlled the seven-segment display directly. The chip contains 8192-bit read-only program memory, a 256-bit random-access memory and a decimal arithmetic logic unit as well as control, timing, and output decoders plus drivers for the display. This gives an overall complexity of roughly 8000 transistors. 

The TMS0972 was introduced mid of the year 1976 and removes all passive components like resistors or capacitors needed with the TMS0952. During the year 1977 the housing of the TMS0972 changed to a shrinked SDIP-28 package. Please notice the different pinout compared to the TMS0972 AP. Please find a picture with all three calculator chips here.

A typical calculator built around the TMS0972 family performs the four basic functions +,-,*,/ and adds the %-function and a four-key memory. 

Family Members and Usage

Type Calculator Digits
TMS0952 TI-1200, TI-1250 sign + 8
TMS0954 TI-1260 sign + 8
TMS0972 TI-1200, TI-1250 8 or sign + 7
TMS0974 TI-1270 8 or sign + 7
TMS0975 Little Professor (1976) 8


Technical Specification

Item Min Typ Max Unit Comments
VSS   0   V   
VDD   -9.0   V   


The TMS0972 ASP uses a shrinked SDIP-28 package.

Pin Description

Pin IO Function Pin IO Function
1 O Digit driver 6 28 O Digit driver 5
2 O Digit driver 7 (MSD) 27 O Digit driver 4
3 O Digit driver 8 (n.c.) 26 O Digit driver 3
4 V Negative Voltage VDD 25 O Digit driver 2
5 I Keymatrix input 1 24 O Digit driver 1
6 I Keymatrix input 2 23   n.c.
7 I Keymatrix input 3 22   n.c.
8 I Keymatrix input 4 21 O Digit driver 0
9 I Key or power on reset 20 V Common Voltage
10 O Segment driver DP 19 I Clock mode
11 O Segment driver G 18 O Segment driver A
12 O Segment driver F 17 O Segment driver B
13 O Segment driver E 16 O Segment driver C
14   n.c. 15 O Segment driver D
The Segment drivers A-G and the Decimal point are connected to a display in the pictured way. 

Keyboard Scanmatrix

The keyboards of all calculators based on the TMS0972 family consist of a x/y-matrix connected to six segment-driver outputs and the keymatrix inputs K1 to K4. The Power on reset is usually not connected to a key.

  K1 K2 K3 K4
Seg. DP MC MR M- M+
Seg. F C +/- % :
Seg. E 7 8 9 *
Seg. D 4 5 6 -
Seg. C 1 2 3 +
Seg. B CE 0 . =


Calculators based on the TMS0972 make use of a 8-digit LED-display with common cathode architecture. The TI-1250 uses the LED-stick 233 without the leading digit populated.

If you have additions to the above datasheet please email:

Joerg Woerner, February 02, 2001. No reprints without written permission.