Texas Instruments TMS0123 Family


With the TMS0102 Texas Instruments introduced end of the year 1971 the first available standard calculator building block on a chip. The chip containes 3520-bit read-only program memory, a 182-bit random-access memory and a decimal arithmetic logic unit as well as control, timing, and output decoders but no drivers for the display. This gives an overall complexity of roughly 5,000 transistors. 

Due to a flexible design concept with both programmable PLA and ROM techniques a lot of design variations appeared. These include two different types of the key-matrix, 8 or 10 digits of 7- or 8-segmented outputs. Even the style of the numbers 4,6 and 9 varied among the family members.

Based on the experience of the TMS0120 developed for the SR-10 some fully floating-point devices derived from the TMS0106 were developed.

Family Members and Usage

Type Calculator Key-Matrix Digits Segment decoder Timing
TMS0123   [+=],[-=] 10 LED
TMS0126 Canon LE-80R, Commodore 3101, Privileg 820  [+=],[-=] 8 LED
TMS0127 Bowmar MX-80 [+=],[-=] 10 LED
TMS0128 Canon LE-82, JCE Percent [+=],[-=] 8 LED


Technical Specification

Item Min Typ Max Unit Comments
VSS   0   V   
VDD -8.1 -7.2 -6.6 V   
VGG -13.2 -14.4 -16.2 V   
IDD   17 25 mA  
IGG   10 15 mA  
CK  100 250 400 kHz  Level between VSS and VGG       


The TMS0123 uses a standard DIP-28 package.

Pin Description

Pin IO Function Pin IO Function
1 I Clock Input 28 V Common Voltage
2 I Keymatrix input P 27 I Keymatrix input Q
3 O Digit driver 1 (LSD) 26 I Keymatrix input N
4 O Digit driver 2 25 I Keymatrix input O
5 O Digit driver 3 24 O Segment driver DP
6 O Digit driver 4 23 O Segment driver H
7 O Digit driver 5 22 O Segment driver G
8 O Digit driver 6 21 O Segment driver F
9 O Digit driver 7 20 O Segment driver E
10 O Digit driver 8 (MSD8) 19 O Segment driver D
11 O Digit driver 9  18 O Segment driver C
12 O Digit driver 10 (MSD10) 17 O Segment driver B
13 O Digit driver 11 (OVER) 16 O Segment driver A
14 V Negative Voltage VDD 15 V Negative Voltage VGG
The Segment drivers A-H and the Decimal point are connected to a display in the pictured way.

Keyboard Scanmatrix

The keyboards of all calculators based on the TMS0102 family consist of a x/y-matrix connected to the digit driver outputs D1-D11 and the key-matrix inputs KN and KO. In the fixed-point output format mode the position of the decimal point is selected with the KP input. The Constant/Chain switch is connected between D10-KQ.

TMS0123, 0126

TMS0127, 0128

D1 1 x2      D1 1 0/00  1   
D2 2 *     D2 2 *  2  
D3 3 :     D3 3 :  3  
D4 4 srq(x)     D4 4 %  4  
D5 5 +=     D5 5 +=  5  
D6 6 -=     D6 6 -=  6  
D7 7 +/-     D7 7 00  7  
D8 8     D8 8 A/D  (8)  
D9 9 .     D9 9 .  (9)  
D10 0 CE    K D10 0 CE  0  K
D11 C     D11 C    


Calculators based on the TMS0102 use all kinds of displays. Texas Instruments introduced together with the calculator chip two pre-configured LED-modules (DIS40, DIS95) based on the TIL360 arrays ,the corresponding segment drivers (SN75491) and digit drivers (SN75492). Most designs make use of these parts.

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If you have additions to the above datasheet please email:

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