DATAMATH CALCULATOR MUSEUM
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DATAMATH CALCULATOR MUSEUM |
Texas Instruments TI-85
| Date of introduction: | January 1995 | Display technology: | LCD dot matrix |
| New price: | $130 | Display size: | 8 * 21 characters |
| Size: | 6.8" x 3.1" x 0.85" 172 x 80 x 21 mm3 |
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| Weight: | 5.8 ounces, 172 grams | Serial No: | 27074117 |
| 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 |
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.
The featured calculator was manufactured in March 1995, two years before it was
discontinued in 1997.
Dismantling
the TI-85 reveals only minor changes compared to a very early calculator
manufactured already in October 1992: The connector of the serial port was moved
slightly and the OTP ROM (One-time Programmable Read-Only
Memory)
replaced with a Mask ROM.
The
calculator electronics
makes still use of six main components on the printed circuit
boards (PCBs):
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 approached 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 ROMs, the program was stored already during the production
of the Integrated Circuit. Later calculators changed to Flash ROMs, 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
Mask ROM LH531GP0©1993
of this TI-85 was manufactured by Sharp, Japan. Please notice the late Copyright
of the ROM, the TI-85 was introduced in 1992. We noticed in early TI-85
calculators a
one-time programmable ROM
RAM (Random Access Memory): The Static RAM is used as data memory and is used to store both variables, user programs and intermediate results. This TI-85 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 and the Calculator-Based Ranger CBR.
The TI-85 was within 2 years replaced with the TI-86.
ROM-Versions:
7.0
8.0
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.
© Joerg Woerner, December 5, 2001. No reprints without written permission.