DATAMATH CALCULATOR MUSEUM

Texas Instruments TI-81

Date of introduction:	January 1995	Display technology:	LCD dot matrix
New price:	$110	Display size:	8 * 16 characters
Size:	6.8" x 3.1" x 0.85" 172 x 80 x 21 mm³
Weight:	5.6 ounces, 168 grams	Serial No:	40069469
Batteries:	4*AAA + CR1620	Date of manufacture:	mth 04 year 1996 (G)
AC-Adapter:		Origin of manufacture:	Taiwan (I)
Precision:	13	Integrated circuits:	CPU: Toshiba T84C00 ASIC: Toshiba TC14L010 ROM: LH5359©1993 RAM: SRM2264 Display: T6A04
Memories:	0-27
Program steps:	2,400 Bytes	Courtesy of:	Joerg Woerner

Texas Instruments changed in 1995 the design of the TI-81, TI-82 and TI-85 slightly, please notice the position of the TI-logo and the color of the type designator. Already one year later, with the introduction of the famous TI-83, the TI-81 was discontinued and the appearance of the TI-82 was updated again.

Dismantling this TI-81 manufactured in April 1996, few months before it was discontinued, reveals no surprises. The hardware looks more or less unchanged compared with a calculator assembled in 1993. There are a lot of rumors that the TI-82 was based on the TI-85 but we have our doubts: This TI-81 and a TI-82 manufactured in January 1994 use an identical printed circuit board (PCB) with just different RAM and ROM chips populated. Learn more about the Hardware Architecture of TI’s Graphing Calculators.

The hardware consists of a Z80 compatible Toshiba T84C00 CPU, a Toshiba TC14L010 ASIC (1.0 micron C-MOS gate array with 1,000 usable gates) for the glue logic, a Sharp LH5359©1993 ROM with 64k Bytes capacity and a Suwa Seikosha SRM2264 Static RAM (SRAM) with 8k Bytes capacity for both user programs and user data.

The driver circuit of the LC-Display was reduced from three Quad-Flat-Pack chips of the original TI-81 to just one bare Toshiba T6A04 chip mounted on a flexible piece of circuit board attached between the display and the main PCB.

As of February 2, 2009 we identified five different hardware architectures of the TI-81:

Year	Date code	Comment	CPU/ASIC	ROM/RAM	Display Driver
1990 (Prototype)	(I-0490)	Engineering Sample	Toshiba T6A49	©1990 1.0 Toshiba TC5565A	2*Toshiba T7778A, Toshiba T7900
1990 (1^st gen)	I-0990	w/o backup battery	Toshiba T6A49A	©1990 1.1 Toshiba TC5565A	2*Toshiba T7778A, Toshiba T7900
1991 (1½^st gen)	I-0991	w/o backup battery	Toshiba T6A43	©1991 1.6 Sharp LH5160	2*Toshiba T7778A, Toshiba T7900
1992 (2^nd gen)	I-1192	with backup battery	Toshiba T6A43	Sharp LH5359©1991 Sharp LH5160	2*Toshiba T6A39 Toshiba T6A40
1993 (3^rd gen)	I-0894	Z80 CPU + ASIC	Toshiba T84C00 Toshiba TC14L010	Sharp LH5359©1993 Suwa SRM2264	Toshiba T6A04
1995 (4^th gen)	I-0496	Z80 CPU + ASIC	Toshiba T84C00 Toshiba TC14L010	Sharp LH5359©1993 Suwa SRM2264	Toshiba T6A04

ROM-Versions:

2.0V

You can check the ROM version of your TI-81 using the following key sequence and reading the number on your screen:

[2nd] [TEST] [ALPHA] [S]

Information provided by ticalc.org and Xavier Andréani.

Exam acceptance:

The TI-81 is permitted (as of September 27, 2007) for use on SAT, ACT, PSAT and AP exams but is not recommended for the AP exam.

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