Texas Instruments TI-83 Plus

This TI-83 Plus made us curious! It was sold on eBay in March 2009 with the date code N-0306I stated in the item description. We requested the ROM-Version of the calculator and the owner reported 1.15 instead the expected 1.19 version, a strange mismatch. We finally acquired the calculator and a first "income inspection" confirmed:

This TI-83 Plus was indeed manufactured by Nam Tai Electronics, Inc. in March 2006 and sports ROM-Version 1.15 released August 2002. We discovered recently a colorful TI-83 Plus manufactured by Nam Tai for the Back-to-School 2007 campaign with a totally new internal construction and couldn't wait to compare them.

Disassembling this TI-83 Plus manufactured in 2006 revealed a big surprise. While Nam Tai's competitor Inventec Corporation improved already in or around 2002 the internal construction of the TI-83 Plus, uses this late calculator still the original design with a discrete Zilog Z84C00 microprocessor instead the later integration into an ASIC.

The original design of the TI-83 Plus made use of 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

CPU:: TheeZilog 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. 

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-83 Plus is based on a later Toshiba gate array family. Learn more about the Hardware Architecture of TI’s Graphing Calculators.

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.

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 stored 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 MX29F400 of this TI-83 Plus was manufactured by Macronix, Taiwan.

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 BS62LV2565 manufactured by Brilliance Semiconductor, Inc. (BSI), Taiwan. The capacity of the memory is 32k Bytes. 

BSI, founded in 1996 and headquartered in the Science-Based Industrial Park in Hsin-Chu, Taiwan, is a fabless semiconductor manufacturing company and a global supplier of ultra low power SRAM.

DISPLAY: The Toshiba T6A04A 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-83 Plus is just 96 * 64 pixel, therefore only one display driver is necessary.

We prepared together with fellow collector Xavier Andréani a comprehensive comparison of entry level graphing calculators, to shed some light on the different specifications of the TI-82 and TI-83 / TI-83 Plus based products.

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. Texas Instruments announced in June 2002 an optional full-sized QWERTY Keyboard for a more convenient entry of notes into the handhelds.


ROM-Versions:

1.15 

You can check the ROM version of your TI-83 Plus 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-83 Plus 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.

© Joerg Woerner, March 25, 2009. No reprints without written permission.