Texas Instruments Compact Computer 40 Plus (PVT)

Texas Instruments introduced in January 6, 1983 with the Compact Computer 40 or CC-40 a battery-operated but yet powerful computer based on an 8-bit microcontroller from the TMS7000 family.

The CC-40 was a result of the "Project X" initiated already in Summer 1977 and leading to the development of the failed TI Programmable 88 and Compact Computer 70 aka CC-70, too.

The CC-40 Plus can operate about 200 hours with its disposable alkaline batteries and keeps programs and user data even when powered off for several months. It was priced similar to programmable calculators like the TI-59 or TI-88 and continued the idea of Solid State Software Modules with its integrated Cartridge Port.

The CC-40 introduced with the HEX-BUS a very innovative port to connect peripherals in a daisy-chain mode very similar to the USB port released more than a decade later. One of the peripherals planned for the Compact Computer family was the HX-2000 Wafertape, a continuous loop tape drive developed by Exatron and known as Stringy Floppy.

The HX-2000 Wafertape had major reliability issue and was never released to the market. Without any other means for mass storage of programs and data, Texas Instruments developed consequently the Compact Computer 40 Plus with an integrated port to connect a cassette audio recorder to save programs or data files on tape.

Texas Instruments dropped out of the home computer market in March 1984 - after selling more than 2.5 million of the famous TI-99/4A - and production of the CC-40 was ceased immediately after. The CC-40 Plus never made it to the market and only a few prototypes from two different Builds or modifications (learn more about the Five Engineering Stages):

It took another two years before Texas Instruments introduced with the TI-74 BASICALC and TI-95 PROCALC the successors of both the TI-88 and CC-40/CC-40 Plus. Five different members of the Compact Computer System are known, only two of them where actually released:

The Compact Computer 40 Plus uses the proprietary HEX-BUS to connect peripherals, eight different products like printers, plotters and even a serial interface were available or planned:

The integrated cartridge port of the Compact Computer 40 Plus supports not only pre-programmed Solid State Software Modules like the TI-59, but allows RAM based Memory Expansions and UV EPROM Program Cartridges. Today we know twelve different cartridges but not all of them were released as of March 1984 when the complete Compact Computer portfolio was discontinued:

Dismantling the featured Compact Computer 40 Plus PVT (Production Validation Test) manufactured in May 1984 by Texas Instruments in their Abilene, TX facility, reveals a neat design with just two printed circuit boards (PCBs) that changed completely from the original CC-40. The orientation of the Main-PCB was reversed with the new design and the components face now downwards instead of upwards. This change allowed not only for soldering the connector for the tape recorder directly onto the Main-PCB, but for a much easier connection to the second PCB with the LC-Display and keyboard contacts. The only differences observed to the CC-40 Plus DVT manufactured in April 1984 seems to be the finish of the housing, both color and printing changed between the two Builds.

The Main-PCB of the CC-40 Plus illustrates still a design with four main building blocks:

CPU (Central processing Unit): The Texas Instruments TMC70C40 microcontroller 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 already well established Intel i8051, Motorola M6801, and Zilog Z8 products. 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). The featured CC-40 Plus PVT uses with the TMC70C40 with ROM-Code 75305 a device with 4k Bytes ROM capacity while the original design of the CC-40 is based on the TMC70C20 equipped with 2k Bytes of ROM. The additional ROM of the microcontroller is mainly used for the low-level functions of the cassette recorder audio interface.

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 HN61256P ROM of this CC-40 Plus was manufactured by Hitachi and offers a capacity of 32k Bytes for the BASIC interpreter.

RAM (Random Access Memory): The RAM is used as data memory and is used to store both variables, user programs and intermediate results. This CC-40 Plus makes use of three HM6116 manufactured by Hitachi, Japan with 2k Bytes capacity, each. The total capacity of the memory is 6k Bytes using three HM6116LP chips, other versions of the CC-40 Plus were planned featuring 18k Bytes of memory using one HM6116LP and two HM6264LP (8k Bytes) chips.

ASIC: The CC-40 Plus uses a TP0373 application-specific integrated circuit (ASIC) with a Date code 8411 designed by Texas Instruments and manufactured in March 1984 in the United States by an unknown company. It contains the "glue logic" to connect the memories, keyboard and LC-Display to the TMC70C40 microcontroller and integrates the Hex-Bus Peripheral port. With the Hitachi HN61256P used with the CC-40 Plus and its Solid State Software Cartridges featuring a rather long access time of up to 3.5 us and the TMC70C40 CPU lacking a "wait-state" mechanism, incorporates the ASIC additional circuitry to slow down the CPU clock cycle while accessing the ROM chips. The TMC70C46 chip used with the TI-74 BASICALC and TI-95 PROCALC integrated all these features and dropped the additional ASIC found with the CC-40/CC-40 Plus design completely.

The front view of the second PCB shows the dot matrix LC-Display with 31 characters width and the contacts of the 61 keys of the keyboard. The back of the second PCB reveals the control and driver electronics for the LC-Display:

DISPLAY: The CC-40 Plus uses like its predecessor CC-40 the 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.

If you have additions to the above article please email: joerg@datamath.org.

© Joerg Woerner, December 29, 2020. No reprints without written permission.