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.

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), %

Item Min Typ Max Unit Comments

V_SS 0 V

V_DD -10.5 -10.0 -9.5 V

V_GG -16.3 -15.8 -15.3 V

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 V_DD 18 O Digit driver 2

12 V Negative Voltage V_GG 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.

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.

KA KB KC KD=KC

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.

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If you have additions to the above datasheet please email: joerg@datamath.org.

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