Texas Instruments TMS0803



With the TMS0803 Texas Instruments introduced in the year 1974 the successor of the TMS0102 single-chip calculator design. In opposite to the TMS0102 with the discrete segment- and digit-drivers the TMS0803 needs only external digit-drivers to drive the seven-segment LED display. The chip contains 3520-bit read-only program memory (320 words x 11 bits), a 1982-bit random-access memory (44 x 4 bits, flags) and a decimal arithmetic logic unit as well as control, timing, and output decoders with segment drivers for the display. This gives an overall complexity of roughly 5,500 transistors.  

Due to a flexible design concept with a programmable ROM some design variations appeared. 

A typical calculator built around the TMS0803 family performs the four basic functions +,-,*, : and adds the %-function. 


Family Members and Usage

Type Calculator Digits Functions
TMS0801 Sinclair Cambridge sign + 8 Constant
TMS0803 TI-1500, TI-2500-II sign + 8 %
TMS0805 Sinclair Scientific sign + 8 UPN 
TMS0806 Exactra 19 6  
TMS0807 Canon LE-85 sign + 8 sqr(x), %



Technical Specification

Item Min Typ Max Unit Comments
VSS   0   V   
VDD -10.5 -10.0 -9.5 V   
VGG -16.3 -15.8 -15.3 V   


The TMS0803 uses a standard DIP-28 package.


Pin Description

Pin IO Function Pin IO Function
1 O Segment driver D 28 O Segment driver C
2 O Segment driver E 27 O Segment driver B
3 O Segment driver F 26 O Segment driver A
4 O Segment driver G 25 O Segment driver DP
5   n.c. 24 O Digit driver 8 (sign)
6 I Keymatrix input A 23 O Digit driver 7 (MSD)
7 I Keymatrix input B 22 O Digit driver 6
8 I Keymatrix input C 21 O Digit driver 5
9 V Common Voltage 20 O Digit driver 4
10 I Keymatrix input D 19 O Digit driver 3
11 V Negative Voltage VDD 18 O Digit driver 2
12 V Negative Voltage VGG 17 O Digit driver 1
13   n.c. 16 O Digit driver 0 (LSD)
14 O Clock 15 V Common Voltage
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 TMS0803 family consist of a x/y-matrix connected to nine digit-driver outputs and the keymatrix inputs KA and KD. 

D0   0 9  
D1   . 8  
D2   % 7  
D3   : 6  
D4   * 5  
D5   - 4  
D6   + 3  
D7 CE = 2  
D8   C 1  


Calculators based on the TMS0803 make use of a 9-digit LED-display with common cathode architecture. 

horizontal rule

If you have additions to the above datasheet please email:

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