Texas Instruments TMC0270

• Features

The TMC0980 family of single-chip calculator circuits was introduced in June 1976 with the two scientific calculators SR-40/TI-30 and the financial calculator Business Analyst of the Majestic product line. The TMC0980 is an extension of the TMS1000 Microcomputer family and allows for highly cost optimized calculators with up to 40 keys and a 9-digit LED Display powered by a 9V battery. Additional cost savings could be achieved by replacing a conventional [ON-OFF] switch with a simple push-button [ON] key. The TMC0980 chip includes 18,432 Bits Read-Only Memory (ROM, 2k*9 Bits) and 576 Bits Random-Access Memory (RAM, 9 Registers * 16 digits), a 4-bit Arithmetic unit, a programmable PLA for segment decoding and both segment and digit drivers for a 9-digit LED Display.

Due to a flexible design concept with both programmable ROM and segment decoder some design variations of the TMC0980 were introduced and Texas Instruments expanded the product family before finally converting the design with the TP0320 from a 9V metal gate PMOS process to a 3V metal gate CMOS process:

• TMC1980: 9-digit, 7-segment VF-Display, 28-pin Package (Dataman)
• TMC0260: 11-digit, 7-segment VF-Display, Thermal Printer Interface, 40-pin Package (TI-5040)
• TMC0270: 9-digit, 14-segment VF-Display, 40-pin Package (Speak & Spell)

The TMC0270 was introduced in June 1978 with the groundbreaking Speak & Spell introducing Solid State Speech™ to Consumer Products. The TMC0270 replaced the segment and digit drivers for a 9-digit, 7-segment LED Display with high-voltage drivers for a 9-digit, 14-segment VF-Display and integrates an interface to the TMC0280 Voice Synthesis Processor. To accommodate these additional features the 28-pin package of the TMC0980 was replaced with a 40-pin package.

• Family Members and Applications

Type Calculator/Product Application Comments
TMC0270/CD2701 Speak & Spell (Spanish Voice) Speaking Educational With TMC0281
TMC0270/CD2702 Buddy, Grillo Parlante, La dictee magique Speaking Educational With TMC0281
TMC0270/CD2704 Speak & Math (1980), Speak & Maths (1980) Speaking Educational With TMC0281
TMC0270/CD2705 Speak & Read Speaking Educational With TMC0281
TMC0270/CD2708 Speak & Math (1981), Speak & Maths (1981) Speaking Educational With TMC0281
TMC0271 Speak & Spell, Speak & Spell (Japan), Radio Shack Spellmaster Speaking Educational With TMC0281
TMC0272 Spelling B (1st Gen) Educational With TMC1984
TMC0273 Mr. Challenger, LETTERlogic (France), LETTERlogic (Germany), LETTERlogic (UK) Educational With TMC0355
TMC0274 Spelling B (2nd Gen), Spelling ABC Educational With TMC0355
TMC0275 Language Translator, Language Tutor Speaking Business With TMC0281
TMC027X Language Teacher Speaking Business With TMC0281


• Architecture

  Description Comments
Architecture Single-chip Calculator Scientific, Financial
Category Digit Processor 4-bit digits
Related TMC0980
7-segment LED-Display
7-segment VF-Display
7-segment VF-Display, Printer
ROM Size 18,432 Bits 2048 Words * 9 Bits
RAM Size 576 Bits 9 Registers * 16 digits
Outputs 9 Digits, 16 Segments Integrated Digit and Segment Drivers
Inputs 5 Keyboard
1 Clock Mode
Segment to Keyboard Scan-Matrix

• Technical Specifications

Item Min Typ Max Unit Comments
VSS   0   V   
VDD   -9.0   V   
VBIAS   -22.0   V   
CK  250 350 450 kHz  Internal oscillator       

• Technology

The TMC0270 a 6 um metal gate PMOS process (metal width = 0.25 mil / 6.0 um, metal spacing = 0.25 mil / 6.0 um, diffusion width = 0.15 mil / 4.0 um, diffusion spacing = 0.30 mil / 7.5 um).

The die size of the TMC0270 is 215 mils * 200 mils / 5.5 mm * 5.1 mm.

• Packaging

The TMC0270 uses either a 0.6” wide 40-pin DIP (Dual In-line Package with a 0.1” / 2,54 mm lead pitch)

or a 0.6” wide 40-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07” / 1.778 mm lead pitch).

• Pin Configuration

Pin IO Function Pin IO Function
1   n.c. 40 V VDD (-9 V)
2 I Keymatrix input P [ON] 39 V VGG (-21 V)
3 I Keymatrix input 1 38 V VSS (0 V)
4 I Keymatrix input 2 37 O Power Down
5 I Keymatrix input 4 36 O CS (TMC0280)
6 I Keymatrix input 8 35 O Digit driver D9 / Seg. AC
7 O Filament driver 1 34 O Digit driver D1 (rightmost)
8 O Filament driver 2 33 O Digit driver D3
9 O Segment driver A 32 O Digit driver D5
10 O Segment driver B,
CTL2 (TMC0280)
31 O Digit driver D7
11 O Segment driver G1,
CTL1 (TMC0280)
30 O Digit driver D8 (leftmost)
12 O Segment driver E,
PDC (TMC0280)
29 O Digit driver D6
13 O Segment driver C,
CTL4 (TMC0280)
28 O Digit driver D4
14 O Segment driver D,
CTL8 (TMC0280)
27 O Digit driver D2
15 O Segment driver I 26 I CLK IN (TMC0280)
16 O Segment driver J 25   n.c.
17 O Segment driver H 24 O Segment driver AP
18 O Segment driver M 23 O Segment driver F
19 O Segment driver K 22 O Segment driver G2
20 O Segment driver L 21 O Segment driver DP
The Segment drivers A-M and DP (Decimal Point) are connected to the display in the pictured way. Some applications use a modified layout with an additional Accent Mark AC, Accent Point (AP), or the Decimal Point to the left. 

• Keyboard Scan-Matrix

The keyboards of all Speech Products based on the TMC0270 family consist of an x/y-matrix connected to up eight outputs with the top row ([ON] key) connected to VSS and the keymatrix inputs K1, K2, K3, K4, and KP. Please keep in mind that the keyboard of the Speak & Spell/Math/Read products are rotated 90 degrees clockwise. 

Example for the original Speak & Spell: 

  K1 K2 K3 K4 KP


Digit 7 F G H I J
Digit 5 P Q R S T
Digit 3 Z / #

Digit 1 OFF GO
Digit 8 A B C D E
Digit 6 K L M N O
Digit 4 U V W X Y

• Display

Product based on the TMC0270 make use of a 8-character or 9-character, 14-segment VF-Display. 

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If you have additions to the above datasheet please email:

© Sean Riddle and Joerg Woerner, April 6, 2021. No reprints without written permission.