Texas Instruments TI-95 PROCALC

Date of introduction:  1986 Display technology:  LCD dot matrix
New price:  $200.00 (SRP 1988) Display size:  16 (10 + 2)
Size:  3.8" x 8.0" x 1.0"
 96 x 204 x 25 mm3
Weight:  10.3 ounces, 290 grams Serial No:  0003685
Batteries:  4*AAA Date of manufacture:  mth 05 year 1987
AC-Adapter:   Origin of manufacture:  Taiwan (I)
Precision:  13 Integrated circuits:  CPU: TMC70011
 ROM: HN61256
 RAM: HM6264
 DISPLAY: HD44780, HD44100
Memories:  900-0    
Program steps:  0-7200 Courtesy of:  Joerg Woerner
    Download manuals:   (US: 25.1M Bytes)
  (US: 48.4M Bytes)

May we call this huge portable computer a calculator? No doubt, the TI-95 Procalc introduced in 1986 is a powerful, keystroke programmable calculator. Some ideas of the early TI-58 calculator and the never introduced TI-88 influenced the TI-95 PROCALC:

TI-95_Modules_1.jpg (33914 Byte)You’ll find an expansion port to install either RAM or ROM-cartridges and you may connect a printer PC-324 through the Dock-Bus to the calculator. 

Already without any expansion the TI-95 features up to 8k Bytes of memory, the expansion adds another 8k Bytes. The display uses a 5*7 dot matrix instead the normal 7-segment design to give full alphanumerical capability. A close relative to the TI-95
PROCALC, the TI-74 BASICALC explains the typewriter style keyboard.

The TI-95 PROCALC System uses the following components:

Part New price Description
PC-324 $115.00 (SRP 1988) 24-column thermal printer
PA-201 (SRP 1988) Power adapter adaptor for TI-74, TI-95
AC9201 $19.00 (SRP 1988) Mains adapter for PC-324
TP-324 $6.00 (SRP 1988) Thermal paper for PC-324
CI-7 $35.00 (SRP 1988) Cassette Interface
CM-8 $50.00 (SRP 1988) 8k Constant Memory Module (RAM)
Mathematics $50.00 (SRP 1988) Library (ROM)
Statistics $50.00 (SRP 1988) Library (ROM)
Chemical Engineering $50.00 (SRP 1988) Library (ROM)
TI-892F $114.95 (SRP 1988) 32k programmed EPROM Module (First)
TI-892D $84.95 (SRP 1988) 32k programmed EPROM Module (Dupl.)
TI-892E $76.95 (SRP 1988) 32k programmed EPROM Module (Bulk)

In 1987 Texas Instruments introduced Programmable Calculator News, a service for TI-74 and TI-95 users to feature program listings, technical articles, question and answer segments, new product reviews, and user comments. All Programmable Calculator News are available for free download as a service provided by the Datamath Calculator Museum.

Dismantling the featured TI-95 PROCALC manufactured in May 1987 by Inventec Corporation in Taiwan, reveals a rather complex design with two printed circuit boards (PCB's). It makes use of three main components on the visible (upper) PCB:

CPU (Central processing Unit): The Texas Instruments TMC70011 microcomputer is a member of the TMS7000 family manufactured in CMOS technology. The original design of the TMS7000 series was introduced in 1981 as an 8-bit extension of the TMS1000 Family to compete with the Intel i8051, Motorola M6801, and Zilog Z8 parts. The first chips sported 128 Bytes of on-chip RAM (Random Access Memory) and either 2k Bytes or 4k Bytes of ROM (Read Only Memory). Later versions, e.g. the TMS70C46 found in this TI-95 PROCALC, integrate 128 Bytes of RAM, 4k Bytes of ROM and add some features like wake-up on key press and the Dock-Bus interface to the TMS70C40.

ROM (Read-Only Memory): The ROM contains the operating system of the calculator or computer. 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 HN61256 ROM of this TI-95 PROCALC was manufactured by Hitachi and offers a capacity of 32k Bytes with a rather slow access time of up to 3.5 us. With the TMC70C40 CPU lacking a "wait-state" mechanism, incorporates the TMC70C46 additional circuitry to slow down the CPU clock cycle while accessing the ROM chips.

(Random Access Memory): The RAM is used as data memory and is used to store both variables, user programs and intermediate results. This TI-95 PROCALC makes use of HM6264 manufactured by Hitachi, Japan
. The capacity of the memory is 8k Bytes.

The second (lower) PCB of the TI-95 PROCALC contains not only the contacts for the keyboard but the complete display assembly:

DISPLAY: The display electronics of the TI-95 PROCALC uses a combination of the Hitachi HD44780 dot-matrix LCD controller with 40 segment and 16 common drivers and one Hitachi HD44100 driver supporting 40 additional segments.


It took only 4 years till Texas Instruments introduced with the TI-81 their first Graphing calculator and another 5 years to the unbelievable TI-92.

Emulating a TI-95

If you don't own a TI-95 calculator - emulate it! 


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© Joerg Woerner, December 5, 2001. No reprints without written permission.