Intel and TI: Microprocessors and Microcontrollers

Two famous companies, Intel and Texas Instruments started about the same time the development of higher integrated microprocessors. Intel continued this development to todays Pentium processors. Texas Instruments stopped the development of pure single-chip microprocessors and added the program and data memories plus the I/O-functions on the chip. The microcontroller was born.

The story is based on the book:

Computer Structures: Principles and Examples
Daniel P. Siewiorek Carnegie-Mellon University
C. Gordon Bell Digital Equipment Corporation
Allen Newell Carnegie-Mellon University

Copyright © 1982 by McGraw-Hill, Inc

• Intel: The birth of the Microprocessor

"In the beginning Intel created the 4004 and the 8008."

• The Prophecy

Intel introduced the microprocessor in November 1971 with the advertisement, "Announcing a New Era in Integrated Electronics." The fulfillment of this prophecy has already occurred with the delivery of the 8008 in 1972, the 8080 in 1974, the 8085 in 1976, and the 8086 in 1978. During this time, throughput has improved 100-fold, the price of a CPU chip has declined from $300 to $3, and microcomputers have revolutionized design concepts in countless applications. They are now entering our homes and cars.

Each successive product implementation depended on semiconductor process innovation, improved architecture, better circuit design, and more sophisticated software, yet upward compatibility not envisioned by the first designers was maintained.

• Historical Setting

In the late 1960s it became clear that the practical use of large-scale integrated circuits (LSI) depended on defining chips having

In 1968, Intel Corporation was founded to exploit the semiconductor memory market, which uniquely fulfilled these criteria. Early semiconductor RAMs, ROMs, and shift registers were welcomed wherever small memories were needed, especially in calculators and CRT terminals, In 1969, Intel engineers began to study ways of integrating and partitioning the control logic functions of these systems into LSI chips. At this time other companies (notably Texas Instruments) were exploring ways to reduce the design time to develop custom integrated circuits usable in a customer's application. Computer-aided design of custom ICs was a hot issue then. Custom ICs are making a comeback today, this time in high-volume applications which typify the low end of the microprocessor market. An alternate approach was to think of a customer's application as a computer system requiring a control program, I/O monitoring, and arithmetic routines, rather than as a collection of special-purpose logic chips. Focusing on its strength in memory, Intel partitioned systems into RAM, ROM, and a single controller chip, the central processor unit (CPU).

Intel embarked on the design of two customer-sponsored microprocessors, the 4004 for a calculator (Intel receives a request from Japan's ETI/Busicom to develop integrated circuits for a line of calculators - the design becomes the 4004 microprocessor) and the 8008 for a CRT terminal (developed for Computer Terminal Corporation - later called DataPoint). The 4004, in particular, replaced what would otherwise have been six customized chips, usable by only one customer. Because the first microcomputer applications were known, tangible, and easy to understand, instruction sets and architectures were defined in a matter of weeks. Since they were programmable computers, their uses could be extended indefinitely.

Both of these first microprocessors were complete CPUs-on-a-chip and had similar characteristics. But because the 4004 was designed for serial BCD arithmetic while the 8008 was made for 8-bit character handling, their instruction sets were quite different.  

• Texas Instruments: They invented the Microcontroller

U.S. Patent Office Rules TI Engineer Invented Computer-On-A-Chip

The U.S. Patent and Trademark Office has affirmed that Texas Instruments engineer Gary W. Boone is the inventor of the single-chip microcontroller, a device that revolutionized electronics by putting all the functions of a computer on one piece of silicon.

The Patent Office ruling, which was just released, is the outcome of a five-year proceeding to determine whether a highly publicized patent awarded in the summer of 1990 to Gilbert P. Hyatt, covered an invention made first by Mr. Boone at TI. The patent office proceeding, known as an interference, focused on who was first to invent the single-chip microcontroller.

 "This ruling rightfully establishes Gary Boone and TI as the inventor of the single-chip microcontroller, settling the broad speculation that followed after Mr. Hyatt received a patent. Gilbert Hyatt has absolutely no claim on the invention," said Richard Donaldson, senior vice president and general patent counsel for TI.

The Patent Office also granted TI's request for a statutory invention registration (SIR), which will officially recognize Gary Boone and TI as the inventor of the single-chip microcontroller. TI  holds several patents covering the commercial implementation of  the computer-on-a-chip, based on work done by Mr. Boone and other TI inventors, resulting from TI's effort in the late 1960s and 1970s on TI's TMS100 and TMS1000 microcontroller families.

 "TI has nothing to gain financially now from receiving another patent on Boone's basic invention of the computer-on-a-chip," explained Mr. Donaldson. "What is important is the Patent Office's confirmation that Gary Boone and TI were first to invent the computer-on-a-chip."

A notice will be attached to Mr. Hyatt's U.S. Patent No. 4,942,516 (Single chip integrated circuit computer architecture) explaining that his claims for invention of the single-chip microcontroller have been canceled.

This ruling will have no effect on TI royalties or its intellectual property licensing program.

The computer-on-a-chip, also known as the single-chip  microcontroller, is a tiny sliver of silicon containing all the essential parts of a computer. Single-chip microcontrollers are widely used in computer keyboards, automatic ignition systems, television and videocassette recorder controls, and other household and industrial applications. Unlike microprocessor chips, single-chip microcontrollers contain on-chip permanent computer programs that direct the chip to perform predetermined functions. Microprocessor chips rely on external program storage devices, such as memory chips or disk drives.

Boone invented the computer-on-a-chip while working on the TMS100 microcontroller chip, which TI introduced commercially in late 1971 (read the original press release here). Unlike the microprocessor chip, which TI and Intel Corporation had each successfully built earlier in 1971, and which is used as the central computing chip in present-day personal computers, the computer-on-a-chip is especially suited to appliance and industrial control applications because it contains a permanent on-chip program that directs the chip to perform a dedicated function, such as controlling a microwave oven or tuning a television.

After months of work, Boone and his coworkers completed building the first working computer-on-a-chip in the early morning hours of July 4, 1971. Two weeks later, TI filed a patent  application, which resulted in the series of patents issued, beginning in 1978, naming Boone as the inventor.

Hyatt never actually built a computer-on-a-chip, but based his claim to the invention on a series of patent applications he filed with the Patent Office in the 1970s and 1980s. In the Patent Office interference proceeding, he claimed he filed the first patent application describing a computer-on-a-chip in December 1970. After a review of tens of thousands of pages of Hyatt's patent filings, however, the Patent Office determined that Hyatt first mentioned the invention in an application that was not filed until December 1977--six years after TI introduced the product.

In 1994, TI requested that the Patent Office publish Boone's patent application as an SIR rather than as an additional patent. An SIR gives official recognition to an invention, but does not entitle the inventor to collect royalties.

Texas Instruments Incorporates.  Dallas, Texas (June 19, 1996)

• TMS1000: The first available Microcontroller

The TMS1000 is actually a series of 4-bit Microcontrollers containing ROM, RAM, I/O, & CPU on one chip produced by Texas Instruments. Find the original press release here. The units are not capable of expansion in any way. The highest clock frequency attainable by the series is 0.4MHz. This results in a 2.5 microsecond clock cycle. All instructions execute in 6 clock cycles. The devices were fabricated using PMOS and required a single -15V supply.

The only data input available is through the 4 bit K input lines. Input instructions collect whatever signals are available on the input lines at the time. Output data exist as 8 O lines and 11, 13, or 16 control, or R lines. The accumulator and the status flag determine the bit pattern of the O lines. This information has to be requested when the chip is produced. What this means is that only 32 distinct patterns can be generated by the O lines. The Y register determines which individual R control line is being set or reset. All of these units have internal clock logic which can be connected to an RC circuit with one end of the capacitor connected to Vss, one end of the resistor connected to Vdd and the opposite ends of the components connected to both OSC1 and OSC2. If an externally generated signal is to be used, it must be connected to OSC1 while OSC2 is grounded. The INIT (reset signal) should be held high for at least 6 clock cycles after power is applied. Reset causes the Page Address and Page Buffer registers to be loaded with binary ones. The O and R outputs as well as the program counter are zeroed.

• The TMS1000 Single Chip Calculators

Because of their limited requirements, hand-held calculators were one of the first consumer-oriented products to take advantage of the emerging LSI technology. After the initial, ad hoc designs, calculators have been implemented as stored-program computers. Today, most calculators consist of a single LSI computer chip plus a display. And the adoption of LSI technology was very rapid. For example, the TI-2500 Datamath calculator introduced in 1973, had 119 parts, of which 82 were electronic in nature. By 1976, the TI-1200 consisted of only 22 parts, of which only the calculator chip (a complete computer with programs) and display were electronic. This single-chip integration is made possible by the tightly specified user environment. Input (e.g., keyboard or magnetic card) and output (e.g., LED display, printer, or magnetic card) options are limited. Further, the input language (i.e., function per key) is also fixed. 

The TMS1001 was the first LSI MOS chip of the TMS1000 family used in the Texas Instruments SR-16 calculator. The chip contains a microcomputer complete with a program ROM having 1,024 eight-bit words; a temporary storage RAM; input (from keypad); output (to control keypad scan and LED display); and an oscillator (clock). The TMS1000 chip was designed to span a range of hand-held calculator products (from four-function up through simple memory calculators). Since the chip had to be customized with the ROM program appropriate to a product, other programmable features were included to improve the chip's flexibility. This programmability was provided by two programmable logic arrays (PLAs). The output PLA converts five bits into twenty 8-bit output patterns in order to conserve program space. These patterns are specified by the calculator designer and represent different output patterns on a seven-segment display. The second PLA is for instruction decoding. The chip provides 16 microinstructions, such as "gate register Y to ALU." Twelve of these microinstructions form the fixed instruction set. The remaining instructions can be formed by combining any of the 16 microinstructions. Thus the instruction set can be specialized to improve ROM efficiency and execution speed for a particular application. Several special features of the microcomputer are aimed at the calculator application. The data paths are 4 bits wide to allow serial processing of binary-code decimal (BCD) digits. The arithmetic functions assume 2's complement integers, special instructions can be formed to facilitate BCD arithmetic (e.g., add six to accumulator for adjustment to legal BCD digits). Another BCD-oriented feature is the RAM addressing, which provides for four words of sixteen 4-bit fields. While the SR-16 only displays eight digits, the extra can he used as "guard" digits to maintain numerical precision or as expansion space for future products with larger displays or exponent displays. (Note that the BCD digit-serial data path allows for this expansion by increasing the loop count on variable-length-dependent operations.) The TMS 1000 applicability is primarily limited by ROM (program), RAM (user-accessible internals and temporaries), speed, and number of I/O pins. All the calculator functions are done by program. Two time-consuming functions are display refreshing and keypad scanning. The monolithic microcomputer must serially refresh the digits of the current display value at a sufficiently high frequency to achieve "persistency." The monolithic microcomputer must also serially examine keypad rows to see if any keys have been depressed. Even simple functions, such as Add, can take several instructions to execute, since BCD digits are addressed sequentially. Due to limitations on the LSI chip density, certain architectural features add to programming complexity:

RAM addressing: Since instruction size is limited to 8 bits, there is not enough room to specify an address in the instruction. Thus, a preloaded register pair (X,Y) is assumed to contain the currently valid address when executing the memory-reference instruction. The register can be updated by using instructions with immediate operands or by incrementing.

Program Counter (PC) incrementing: In order to save a separate incrementer for the PC or trips through the ALU for updating, the PC update is implemented by a pseudo-random sequence to go through all 64 states produced by a feedback shift register such as is used in cyclic redundancy codes. Thus only a shifter and several logic gates are required.  

Instructions with side effects: Certain instruction op codes have been selected so that they can apply appropriate constants to the ALU and RAM. While this saves ROM space for frequently used constants, it seems to make op code selection difficult and add non-symmetry to the instruction format.  

•  All TMS1000 chips

The TMS1000 was introduced in 1974 and used in the SR-16 calculator. The following table summarizes the 15 different chips used in TI single-chip calculators.