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Texas Instruments TI-85 ViewScreen™ (1994)

Date of introduction:	October 1994	Display technology:	LCD dot matrix
New price:		Display size:	8 * 21 characters
Size:	6.8" x 3.1" x 0.85" 172 x 80 x 32 mm³
Weight:	7.7 ounces, 218 grams	Serial No:	VS270530
Batteries:	4*AAA + CR1620	Date of manufacture:	mth 03 year 1995 (G)
AC-Adapter:		Origin of manufacture:	Taiwan (I)
Precision:	14	Integrated circuits:	CPU: Toshiba T6A43 ROM: LH531©1993 RAM: SRM20256 Display: 2*T6A39, T6A40
Memories:
Program steps:	28k Bytes	Courtesy of:	Joerg Woerner

The TI-85 followed the famous TI-81 and sports a larger user memory. The size of the display was increased to 64 * 128 pixel.

The main features of the TI-85 in a short summary:

• Graphing of up to 99 functions at one time.
• Parametric graphing to analyze up to three parametric equations.
• Manipulation of three matrices with dimensions of 30*30.
• One- and two-variable statistical analyses with up to 2800 data points.
• Up to 37 programs with a total of 28000 bytes.

The TI-85 ViewScreen Calculator (VSC) is the teacher version of the standard TI-85. It connects with a special port to a ViewScreen panel via a cable. Placing the panel on the overhead projector enlarges the image of the handheld screen so that each student can follow along. Don't miss the first generation TI-85 VSC permanently connected to a much smaller Panel.

Four ViewScreen panels were available in 2008:

• Panel 1: TI-73 VSC, TI-73 Explorer VSC, TI-80 VSC, TI-82 VSC, TI-83 VSC,
TI-83 Plus VSC, TI-83 Plus Silver Edition VSC, TI-84 Plus VSC,
TI-84 Plus Silver Edition VSC
• Panel 2: TI-89 VSC, TI-89 Titanium VSC, TI-92, TI-92 Plus, Voyage 200
• Panel 3: TI-85 VSC (2^nd design), TI-86 VSC
• Panel 4: TI-Nspire, TI-Nspire CAS, TI-Nspire Touchpad, TI-Nspire CAS Touchpad

As an alternative the TI-Presenter video adapter connects to a TV or other projection device with a video input port.

From a technical point of view the second generation TI-85 VSC is almost identical with the students TI-85. The main difference you notice is a two piece bottom shell of the calculator housing to accommodate the ViewScreen electronics. Please notice that the red "blue wire" to rectify a design issue with the calculator stayed even over multiple Revisions of the TI-85 VSC in place.

Dismantling the featured TI-85 VSC manufactured in March 1995 by Inventec Corporation in Taiwan reveals a small printed circuit board (PCB) with one additional driver chip connected in a piggy back manner to the display board of the calculator.

The main electronics of the TI-85 VSC is centered around the well-known Toshiba T6A43 Application Specific CPU, the 8k Bytes RAM chip used in the TI-81 was replaced with a 32k Bytes chip and the capacity of the ROM (Read-Only Memory) was doubled from 64k Bytes to 128k Bytes.

It makes use of just six main components on the printed circuit boards (PCB’s):

CPU (Central processing Unit): The Toshiba T6A43 is a so-called Application Specific CPU and combines a Z80 core with an ASIC (Application Specific Integrated Circuit). You’ll find different approaches within the graphing calculator line of Texas Instruments, sometimes the use of an individual CPU (e.g. Z80 and M68000) with a supporting ASIC or – like with this TI-85 - the integration of the CPU into the ASIC. Learn more about the Hardware Architecture of TI’s Graphing Calculators.

ROM (Read Only Memory): The ROM contains the operating system of the calculator. The first products on the market used mask-programmable ROM’s, the program was stored already during the production of the Integrated Circuit. Later calculators changed to Flash ROM’s, a technology allowing the programming of the software during the final production stage of the calculator. With the TI-83 Plus and all later graphing calculators from Texas Instruments even the user was able to reprogram the operating system.

RAM (Random Access Memory): The RAM is used as data memory and is used to store both variables, user programs and intermediate results. This TI-85 VSC makes use of SRM20256 manufactured by Suwa Seikosha, Japan. The capacity of the memory is 32k Bytes.

DISPLAY: The two Toshiba T6A39 are column drivers for small-to-medium-sized dot matrix graphic LCD’s, while the T6A40 is a row driver. They are compatible with Z80 based CPU’s and drives displays with up to 80 columns, resp. 68 rows. The display size of the TI-85 is 128 * 64 pixel, therefore a total of three drivers are necessary.

A serial port of the calculators allows the connection to the Calculator-Based Laboratory system CBL, its successor CBL 2, the Calculator-Based Ranger CBR and its successor CBR 2.

About one year later with the TI-86 a even more powerful successor was introduced.

ROM-Versions:

9.0
10.0

You can check the ROM version of your TI-85 using the following key sequence and reading the number on your screen:

[2nd] [MODE] [ALPHA] [S]

Information provided by ticalc.org and Xavier Andréani.

Exam acceptance:

The TI-85 is permitted (as of September 27, 2007) for use on SAT, ACT, PSAT and AP exams.

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