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Texas Instruments TI-81

Date of introduction:  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:  2400 Bytes Courtesy of:  Joerg Woerner

TI-81_2_Back.jpg (142117 Byte)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.

TI-81_2_PCB.jpg (361571 Byte)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.

TI-81_2_Memory.jpg (228218 Byte)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 RAM with 8k Byte capacity for both user programs and user data.

TI-81_2_LCD.jpg (95687 Byte)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
(1st gen)
I-0990 w/o backup battery Toshiba T6A49A ©1990 1.1
Toshiba TC5565A
2*Toshiba T7778A, Toshiba T7900
1991
(1½st gen)
I-0991 w/o backup battery Toshiba T6A43 ©1991 1.6
Sharp LH5160
2*Toshiba T7778A, Toshiba T7900
1992
(2nd gen)
I-1192 with backup battery Toshiba T6A43 Sharp LH5359©1991
 Sharp LH5160
2*Toshiba T6A39
Toshiba T6A40
1993
(3rd gen)
I-0894 Z80 CPU + ASIC Toshiba T84C00
Toshiba TC14L010
Sharp LH5359©1993
Suwa SRM2264 
Toshiba T6A04
1995
(4th gen)
I-0496 Z80 CPU + ASIC Toshiba T84C00
Toshiba TC14L010
Sharp LH5359©1993
Suwa SRM2264 
Toshiba T6A04

ROM-Versions:

TI-81_I0496G_OS.jpg (49953 Byte)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.  

 

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

© Joerg Woerner, February 8, 2008. No reprints without written permission.