General Instrument Calculator Integrated Circuits

General Instrument (GI) was founded in 1939 as a manufacturer of electronics equipment, headquartered in Horsham, Pennsylvania. GI ventured in 1960 with the acquisition of General Transistor Corp. of New York into the semiconductor business, manufacturing germanium transistors in high volume for consumer electronics like television sets. GI was one of the forerunners in developing Integrated Circuits (ICs) in PMOS (p-channel Metal–oxide Semiconductor) technology and operated as of 1969 RnD Centers in Hicksville, NY and Glenrothes, Scotland. Later acquisitions included the Philco-Ford IC assembly factory in Kaohsiung, Taiwan and a brand-new semiconductor plant in Chandler, Arizona out of the bankruptcy of Bowmar. These two acquisitions allowed GI to manufacture low-cost, high-yield PMOS chips needed for consumer electronics.

Three of GI’s activities were operated in 1969 under the General Instrument Microelectronics umbrella, headquartered in Hicksville, NY:

It must have been a shockwave for a handful of Japanese companies, when Texas Instruments demonstrated in 1967 with the Cal-Tech feasibility study for the first time the application of LSI (Large Scale Integration) chips for portable, battery-operated calculators. American companies not only invented the transistors and ICs (Integrated Circuits) used with electronic calculators in the second half of the 1960s, but they also had a lead in the design and manufacturing of chips using PMOS (p-channel Metal–oxide Semiconductor) technology. On the other hand, Japanese companies like Canon, Casio, Sanyo, Sharp and Toshiba almost completely owned in 1967 the market of electronic desktop calculators and successfully developed, manufactured and sold their products designed around transistors and ICs.

The major manufacturers of electronic desktop calculators acted swiftly and locked into relationships with chips manufacturers capable of designing and producing PMOS LSI devices. In a first wave, around 1969/1970, three successful results of these collaborations hit the market and brought GI the first time into our Famous Three list:

The Sanyo ICC-82D made use of a Chipset developed and manufactured by General Instrument Microelectronics operations in Glenrothes, Scotland and consisted of four LSI chips in a 12 um process and mounted into 36-pin Quad-In-Line ceramics packages. The underlying logic of the Chipset was mainly developed by Sanyo Electric Co. engineers in Japan while the translation into transistors, chip layout, manufacturing, testing and packaging of the devices was handled by General Instrument Microelectronics. Sanyo used the four chips, named LM8001 to LM8004 in other calculators like the ICC-804D, too – eventually replacing the LM8004 chip with the LM8005.

Sanyo started later to manufacture the LM8000 Chipset under a license agreement with General Instrument Microelectronics in their newly-build semiconductor plant in Japan. General Instrument Microelectronics on the other hand grew quickly into a well-respected manufacturer for high-volume PMOS devices and developed many different Chipsets for calculator manufacturers like Advance Electronics Ltd. and Diehl Calculating Systems.

However, the big breakthrough for GI in the calculator chip business is a different "Silicon Glen" storyline. Most of us are familiar with Silicon Valley, a region in Northern California that was and still is a center for high technology and innovation. Silicon Glen is the nickname given to the high tech sector of Scotland and having its origins in the electronics business with Ferranti establishing a plant in Edinburgh in 1943 and major US companies like Honeywell, IBM and NCR joining later. Semiconductor design and manufacturing started in Silicon Glen around 1960 with Hughes Aircraft manufacturing germanium and silicon diodes. Elliott Automation started in Glenrothes in 1966 manufacturing their first bipolar Integrated Circuits in RTL (Resistor-Transistor Logic) and DTL (Diode-Transistor Logic) technology and opened in 1967 a MOS research laboratory. In 1967 Elliott Automation merged with English Electric, and when GEC bought English Electric in 1969 they decided to close their production plant in Glenrothes. A small core team of former Elliott Automation employees foresaw these moves already in 1967 and successfully offered their services to General Instrument to establish a new facility for design and production of MOS ICs.

General Instrument opened in 1969 a wafer fab in Glenrothes, followed within a few months by Motorola, National Semiconductor and Signetics. Consequently, Compugraphic relocated its headquarters from London to Glenrothes, providing photomask manufacturing for the chip manufactures in Silicon Glen.

With all the necessary ingredients, sans money, for a successful startup available, four General Instrument design engineers – all former employees of Elliott Automation - left in 1970 to form Pico Electronics Ltd. to realize their vision of a "single-chip calculator circuit" that they couldn’t pitch successfully to their former managers. It was no other than the CEO of GI providing the Pico Electronics team with startup capital under an extremely smart deal: If the design idea works out as envisioned, Pico Electronics would grant General Instrument the exclusive rights to manufacture and sell the chips on a global base. Enter PICO1.

PICO1 aka 76250 aka GI 250

The Pico Electronics team was very experienced with developing Chipsets used with electronic calculators, typically using between four and six chips with "hard-coded" logic for the different building blocks. These designs provided almost no flexibility for even minor modifications of the feature set of an electronic calculator and each design used its own set of photomasks for manufacturing. The newly formed Pico Electronics team came up with the idea for a "software-defined" calculator architecture, similar to larger computer systems and using ROM (Read-Only Memory) for its program, RAM for its data and a small, embedded RISC (Reduced Instruction Set Computer) CPU (Central Processing Unit) for the algorithm. It took the engineers at Pico Electronics only one year from starting their company to send their first design out to GI for manufacturing and it worked almost perfectly on the first run. While Pico Electronics was fixing some design bugs, General Instrument started in June 1971 quietly some marketing activities for their first "single-chip calculator circuit", simply named GI 250. Certainly not the World’s first single-chip calculator circuit, it turned out that Mostek was faster and announced already in November 1970 their MK6010, developed under a contract for Japanese calculator manufacturer Nippon Calculating Machines and basically integrating the “hard-wired” logic of 22 MSI (Medium Scale Integration) and SSI (Small Scale Integration) chips used the earlier NCM’s earlier Busicom Junior calculator into a single LSI chip containing around 2,200 MOS transistors.

The GI 250 brought General Instrument a second time into our Famous Three list, this time for their first single-chip calculator circuit:

Pico Electronics made some interesting design choices with the development of the PICO1 chip, both with the user interface and the embedded calculating logic, but certainly with the implementation of the calculator circuit.

User Interface:

Calculating Logic:

Logic Implementation:

Despite its commercial availability about three months before Texas Instruments' groundbreaking TMS0100 Product Family, had the original PICO1 chips GI 250 and GI251 only modest success and as of today we know with the Litton Royal Digital III and Digital IV calculators only two early design wins. In 1972, the GI 251F made its way into the Litton Royal Digital III and Monroe 20 calculators. After renaming the GI 251F in a marketing campaign to C-500, the PICO1 started to take off with multiple design wins, most notably the Commodore US 1 and various Iain Jones International, Litton Royal, Sanyo, Unisonic and Universal Data Machine calculators.
The GI 250, GI 251F and C-500 are manufactured in a 25-Volt, 12 um metal gate PMOS process with enhancement mode transistors used for both gates and loads and using Ceramic Dual In-line Packages (CDIP) with 24 pins.

The C-500 was soon followed with the C-550 after converting the original 25-Volt PMOS process to a revised 15-Volt PMOS process and the PICO1 architecture made its way into the famous Sinclair Executive and Cambridge calculators.

To reduce the component count associated with the multiplexed digit outputs of the original PICO1 design, General Instrument introduced with the C-560 and C-570 series two variations with eight digit outputs while ITT offered with the 7105N a companion chip for the C-550, integrating the demultiplexer and digit drivers into an economical 18-pin package.

General Instruments' last – and most successful – improvement of the original PICO1 design was introduced with the CZL-550 in 1974, supporting not only "leading zero suppression" to reduced current consumption of the calculator but integrating segment drivers for the seven-segment LED display.

The combination of the CZL-550 and ITT's 7105N demultiplexing digit driver chip allowed during the height of the "Calculator Wars" a very low Bill-of-Material – for some customers a higher priority than the flawed User Interface and Calculating Logic implementation of the once revolutionary PICO1 design dating back to 1971.

Obviously both General Instrument's marketing team and Pico Electronics design team knew about their vulnerability, and they joined forces to introduce in Fall 1973 their C-593 and CF-593 chips, boldly advertised as "socket-compatible" with Texas Instruments’ TMS0803 and TMS0855, respectively. This made the design-in phase of the C-593/CF-593 very easy for the calculator manufacturer but General Instrument had an ace up their sleeve - the C-593 was just one member of a multi-dimensional Product Portfolio ranging from 8-digit four-function calculators to 9-digit scientific calculators using either LED Displays or VF-Displays and operated with 9 Volt or 15 Volt supplies. All in one standardized, TMS0800 compatible pinout!

When General Instrument published in 1978 their final Data Catalog featuring Calculator Chips, the Product Family grew to over 30 members in a two-dimensional Portfolio Chart..

General Instrument C/CF-580, C/CF-590 and C/CF-680 Series - Display and Power Supply:

General Instrument C/CF-580, C/CF-680 and C/CF-590 Series - Calculator Function:

General Instrument’s final calculator chip development was the C-680D/C-1680D series, integrating not only the segment drivers for LED displays, but also the digit drivers and hence allowing "true single-chip calculator designs".

General Instrument C-680D and C-1680D Series - Calculator Function: