Texas Instruments TI-73 ViewScreen™

Date of introduction:  1998 Display technology:  LCD dot matrix
New price:  $150.00 (SRP 2008) Display size:  8 * 16 characters
Size:  7.2" x 3.2" x 0.95"
 182 x 81 x 24 mm3
Weight:  6.6 ounces, 186 grams Serial No:  VS 011915
Batteries:  4*AAA + CR1620 (35mA) Date of manufacture:  mth 05 year 1998
AC-Adapter:   Origin of manufacture:  Taiwan (I)
Precision:  14 Integrated circuits:  CPU: Zilog Z84C0008
 ASIC: TI REF 9815455
 Flash: AM29F400
 RAM: SRM2B256
 Display: Toshiba T6A04
Program steps:  25k Bytes, 128k Bytes Flash ROM Courtesy of:  Joerg Woerner

TI-73VSC_BACK.jpg (231781 Byte)The TI-73 ViewScreen Calculator (VSC) is the teacher version of the standard TI-73. 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.

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 (2nd 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 TI-73 VSC is almost identical with the students TI-73. The main difference you notice is a bulgier bottom shell of the calculator housing to accommodate the ViewScreen electronics and connector. Dismantling the TI-73 VSC reveals a small printed circuit board (PCB) with two driver chips connected with a flexible cable to the display PCB of the calculator.

Disassembling this TI-73 VSC manufactured in May 1998 reveals the original design of the TI-73 using 5 main Integrated Circuits:

Zilog Z84C00 microprocessor
TI REF 9815455 ASIC
512k Bytes Flash ROM
32k Bytes RAM
Toshiba T6A04: Single-chip 64*120 pixel display driver

TI-73VSC_CPU.jpg (174113 Byte)CPU (Central processing Unit): This TI-73 VSC is centered around a Zilog Z84C0008 microprocessor, a low-power CMOS-version of the original Z80 developed in 1974 and introduced in 1976. It is probably the same design as the Toshiba TMPZ84C00 chip found in some graphing calculators.

TI-73VSC_ASIC.jpg (339225 Byte)ASIC (Application Specific Integrated Circuit): The Z80 is a pure microprocessor and lacks, compared to so-called microcontrollers, any peripherals and housekeeping circuits. Texas Instruments developed already for the TI-82 in 1993 a support ASIC for the Z80 microprocessor based on the Toshiba TC14L gate array family with 1,000 usable gates in 1.0um CMOS-technology. This chip-set replaced the Toshiba T6A43 Application Specific CPU found in the earlier TI-81 designs. We assume that the TI REF 9815455 ASIC used in this TI-73 VSC is based on a later Toshiba gate array family. 

Within the graphing calculator line of Texas Instruments you find different approaches for the CPU architecture:

Application Specific CPU, e.g. the T6C79 found in the TI-83
Discrete CPU with support ASIC, e.g. the Z80 / TI REF 9815455 combination of this TI-83 Plus
Gate array with embedded processor core and RAM, e.g. the TI REF 738X
   found in this TI-83 Plus manufactured by Inventec Corporation in 2006.

TI-73VSC_ROM.jpg (135538 Byte)ROM (Read Only Memory): The ROM contains the operating system of the calculator. The first products on the market used mask-programmable ROM, the program was strored already during the production of the Integrated Circuit. Later calculators changed to Flash ROM, 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. The Flash-ROM 29F400 of this TI-83 Plus was manufactured by Fujitsu, Japan.

TI-73VSC_RAM.jpg (138347 Byte)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-83 Plus makes use of one SRM2B256 chip manufactured by EPSON, Japan. The capacity of the memory is 32k Bytes.

DISPLAY: The Toshiba T6A04 is a column and row driver for small-to-medium-sized dot matrix graphic LCD. It is compatible with Z80 based CPUs and drives displays with up to 120 columns and 64 rows. The display size of the TI-73 VSC is just 96 * 64 pixel, therefore only one display driver is necessary.

The design of the TI-73 influenced even the TI-82 and TI-83, please focus on the rounder shape of the keys. In 2003 the color of the housing was changed to match with the TI-15 Explorer and the nameplate changed to TI-73 Explorer.

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.

Don't miss the colorful slide cases developed for the TI-83 Plus, they fit on the TI-73 ViewScreen, too.


TI-73VSC_OS.jpg (52658 Byte)1.3004
1.60 (December 16, 2001)
1.90 (February 6, 2006)
1.91 (March 20, 2008, actual in February 2009)

You can check the ROM version of your TI-73 VSC using the following key sequence and reading the number on your screen:

[2nd] [MEM] [1]

Information provided by and Xavier Andréani.

Exam acceptance:

The TI-73 VSC 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 Woerner, August 9, 2009. No reprints without written permission.