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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
Memories:      
Program steps:  25k Bytes, 64k 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.

Three ViewScreen panels were available in 2003:

Panel 1: TI-73 VSC, TI-80 VSC, TI-82 VSC, TI-83 VSC,
   TI-83 Plus VSC, TI-83 Plus Silver Edition VSC
Panel 2: TI-89 VSC, TI-92, TI-92 Plus, Voyage 200
Panel 3: TI-85 VSC (2nd design), TI-86 VSC

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 Byte Flash-ROM
32k Byte 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 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.

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.


ROM-Versions:

TI-73VSC_OS.jpg (52658 Byte)1.3004
1.3007
1.60 (December 16, 2001)
1.90 (February 6, 2006, actual in February 2008)
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 ticalc.org 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@datamath.org.

© Joerg Woerner, August 9, 2009. No reprints without written permission.