Texas Instruments TI-74 BASICALC

Date of introduction:  1986 Display technology:  LCD dot matrix
New price:  $135.00 (SRP 1988)
 DM 348.00
Display size:  31 (10 + 3)
Size:  3.8" x 8.0" x 1.0"
 96 x 204 x 25 mm3
Weight:  10.3 ounces, 290 grams Serial No:  0001522
Batteries:  4*AAA Date of manufacture:  mth 06 year 1987
AC-Adapter:   Origin of manufacture:  Taiwan (I)
Precision:  13/14 Integrated circuits:  CPU: TMC70009
 ROM: HN61256
 RAM: HM6264
 DISPLAY: HD44780, HD44100
Memories:  8kB RAM, 32kB ROM    
Program steps:   Courtesy of:  Joerg Woerner
Download leaflet:   (US: 1.7M Bytes)    

The TI-74 BASICALC is a cross-over of the earlier CC 40 Compact Computer and a conventional calculator.
You have both a BASIC-language computer with a total of 8k Byte memory and a calculator mode with algebraic input and immediate output on the huge alphanumerical display.

The other features of the TI-74 are similar to its sibling TI-95 PROCALC:

You may install RAM or ROM-cartridges in the expansion port or connect the PC-324 printer through the Dock-Bus to the computer. The maximum capacity of the TI-74 BASICALC is 16k Bytes of memory.

 The TI-74 BASICALC 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)
Learn Pascal $50.00 (SRP 1988) Library (ROM)
Finance $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-74 BASICALC manufactured in June 1987 by Invented 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 TMC70009 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 used with this TI-74 BASICALC, 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-74 BASICALC 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-74 BASICALC makes use of HM6264 manufactured by Hitachi, Japan
. The capacity of the memory is 8k Bytes.

: The display drivers of the TI-74 BASICALC are located on the second (lower) PCB and use a combination of a Hitachi HD44780 LCD Controller and one additional Hitachi HD44100 LC Driver. The HD44780 contains the character generator for 208 characters in a 5x8 dot matrix, 32 characters in a 5x10 font, RAM for a maximum of 80 characters and the driver electronics for 16 characters. The HD44100 adds an additional 40 segment drivers for the remaining characters.


A special OEM-version of the TI-74 was sold as TI-74S and TI-74S ALLIANZ. Interested in customizable calculators and computers or even Programmable Data Terminals? Don't miss the TI-78 and TI-78P.

The TI-74 BASICALC is featured in the Texas Instruments Incorporated bulletin CL-893 dated 1986.


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If you have additions to the above article please email:

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