Gary Boone, who worked in the MOS division of Texas Instruments (TI), designed the first chip that could be called a microcontroller because he was bored with his job and his family was in trouble. He joined TI in 1969, when calculator chips were becoming a big business. In the 1960s, electronic calculators replaced the Marchant and Frieden electromechanical calculators that had dominated the market for decades. Semiconductors enabled the replacement of hundreds of complex metal and plastic parts in electromechanical calculators, first with hundreds of transistors and diodes, and then with fewer and fewer integrated circuits. North American Rockwell Microelectronics, Mostek, General Instrument, and Texas Instruments were early players in the multi-chip calculator market.
Initially, dozens of integrated circuits were needed to replace hundreds of transistors and diodes. As more components were included in the ICs, fewer ICs were needed to build a usable calculator. By 1968, IC-based calculator designs had largely replaced transistor-based designs. The end point was obvious. Eventually, semiconductor manufacturers would reduce the electronic core of a calculator to a single chip.
Japanese calculator suppliers Sharp, Canon and Busicom partnered with various U.S. semiconductor suppliers to develop custom chips for their calculators. Sharp partnered with Rockwell, Canon partnered with TI, and Busicom partnered with Mostek and Intel to develop different models of calculators. Busicom asked Mostek to develop single-chip calculators and contracted with Intel to develop custom chipsets for more complex programmable calculators. Mostek first achieved this goal in late 1970 with the introduction of the The MK6010, a custom chip that replaced 22 integrated circuits, was integrated by Busicom into its small, four-function desktop calculator, the Busicom Junior. The contract with Intel eventually led to the development of the Intel 4004 microprocessor. This story, however, is about microcontrollers, which took a related but different evolutionary path.
TI’s MOS division was deeply involved in the affairs of calculator chipsets. Calculator companies, including Canon, Olivetti and Olympia, asked TI to develop 4, 5 and 6 chipsets for their calculators. The implementation of these custom chip projects fell on the shoulders of several TI engineers, including Gary Boone. The job required flying around the world to Japan, Italy and Germany. Boone spent a lot of time on the road, and his family was unhappy with his absence. boone soon grew tired of the intense travel just to develop a new chipset that looked a lot like the previous one. In those days, many potential customers wanted calculator chips, but each customer wanted something a little different. That’s the nature of the custom chip business. It was a customer-intensive industry.
Boone’s frustration and family commitments led him to Daniel Baudouin, the MOS marketing manager at TI, and together they compiled a matrix of customer requirements that came from working with different calculator manufacturers. Boone and Baudouin also took note of what the current TI MOS process technology could accomplish and what it could do best. Their thinking quickly turned to architectures that make heavy use of memory (RAM and ROM) because these structures are extremely efficient, easier to wire on the IC, and memory promises to improve silicon utilization by a factor of 40 or 50.
Once Boone and Baudouin started thinking about using memory, they began to consider how much data and program storage space a calculator chip would need. At that point, the TI team began discussing the prospect of a ROM-programmable single-chip calculator with potential customers. They were met with a lot of opposition. Customers accustomed to funding their own calculator chips were hesitant to the idea of a calculator chip that was differentiated only by certain bits in the on-chip ROM. there was also opposition within TI because ROM-based programmable parts were the opposite of what the company was used to making.
As you read this, you may notice that all the discussion of calculator chips is inconsistent with the title. This series of articles is clearly about the history of microcontrollers. Let me assure you that we are not off track. The earliest microcontrollers were designed by Boone and TI engineer Michael Cochran and included the processor, memory (RAM and ROM) and I/O all on one piece of silicon, the calculator chip, and they were the earliest microcontrollers. See the figure below, taken from U.S. Patent 4074,351:
This figure shows the block diagram of the TMS1802NC, TI’s first microcontroller calculator. It shows all the key components of the microcontroller. It has a CPU consisting of a program counter (PC), instruction registers (IR), instruction decoders (Control Decoders), and a 4-bit ALU. It has a RAM to store numerical data and a ROM to store the program that defines the operation of the chip. Finally, at the bottom, you can see the dedicated I/O circuitry for scanning the matrix keyboard, driving the display digits and driving the seven segments in each display digit. The I/O in this design may be specialized, but this diagram clearly depicts a microcontroller.
On September 17, 1971, TI released the TMS1802NC monolithic calculator integrated circuit. Two months later, Intel released the 4004 microprocessor. Texas Instruments priced this device at less than $20. The ROM contained 320 11-bit instruction words (3520 bits), while the serially accessible 182-bit RAM contained three 13-bit BCD (binary coded decimal) digits and 13 binary flag bits. The chip requires a total of about 5,000 transistors.
(Note: In researching this article, I found more than one site that confused TI’s TMS1802NC 4-bit calculator chip with the 8-bit RCA CDP1802 COSMAC CMOS microprocessor released in 1974. the TI and RCA chips are not the same part, although the part numbers are similar.)
TI’s press release from September 17, 1971 further confirms the TMS1802NC’s status as a microcontroller:
“TI’s single-level mask programming technique using the same base or host design allows any number of special operating features to be easily implemented. The only limitations are the size of the program ROM, RAM storage and control, timing and output decoders. For example, by reprogramming the output decoder, the TMS1802 can be used to drive decimal displays, such as Nixie-type tubes.”
One of the first calculators to use TI’s TMS1802 calculator chip was the Sinclair Executive.
TI released the TMS0100 microcontroller calculator family on September 20, 1972, almost exactly one year after the release of the TMS1802C. The company rebranded the TMS1802NC as the first member of the TMS0100 family, the TMS0102. Eventually, the family would have more than 15 different members made from TI’s 10-micron PMOS process technology. A year later, Mostek released an improved, pin-compatible copy of the TMS0102, the MK5020. Like all of the semiconductor manufacturers listed at the beginning of this article, TI and Mostek would soon release microcontrollers developed in part with knowledge gained from the creation of these early calculator chips.
In the meantime, Boone has stepped outside of this calculator box. Calculator chip patent 4,074,351 describes other target applications, including cab meters, digital voltmeters, event counters, car odometers and measuring scales. Of course, microcontrollers have been used in all of these applications and much more.
Like many first-of-its-kind devices, Texas Instruments’ TMS0100 family of calculator chips is a narrowly focused microcontroller, used primarily to make calculators. However, the first chip in the TMS0100 family, originally called the TM1802NC and later renamed the TMS0102, contained everything a microcontroller needed: CPU, RAM, ROM, and I/O. It was, of course, a specialized microcontroller. Its I/O was application specific and was designed to connect to a matrix keyboard and a seven-segment display. The TMS1802NC, however, is a microcontroller.
Originally conceived by Gary Boone and Daniel Baudouin of Texas Instruments and then implemented by Boone and Michael Cochran, Texas Instruments introduced the TMS0100 family on September 20, 1972, and these chips quickly took over the calculator market. ti suddenly had a whole new world to conquer. The company quickly realized that if the same programmable silicon could be designed to be generic enough, it could serve multiple markets. ti applied the experience it had gained from its initial programmable calculator chips to produce the first general-purpose microcontrollers, the TMS1000 family, which was released in 1974.
The TMS1000 microcontroller family has some similarities to the TMS0100 programmable calculator family, but also has many differences. Both devices have a 4-bit CPU and a Harvard architecture, which provides separate address spaces for RAM and ROM. Harvard architectures were common in early microcontroller designs because they simplified the design of the microcontroller’s RAM, ROM, address decoder, and data bus. However, in my opinion, the Harvard architecture complicates the life of the programmer who must keep track of two different address spaces and must often design ways to move data from ROM to RAM. (Fortunately, there is no point in transferring data from RAM to ROM; the data will not complete the process. You can’t successfully write to a masked ROM.)
Unlike the TMS0102’s 3250-bit ROM (organized as 320 11-bit words), the first TMS1000 microcontroller had a 1-kilobyte ROM organized as 1024 8-bit words. Thus, the TMS0100 and TMS1000 families start with incompatible 11-bit and 8-bit instruction sets, respectively. Similarly, the TMS0102 has a 182-bit serial RAM containing three 13-bit numbers in BCD (Binary Coded Decimal) format and 13 binary flags, while the TMS1000 microcontroller has a 256-bit RAM organized into 64 4-bit words.
According to the TMS1000 documentation, the 64 4-bit words stored in RAM “are conveniently grouped into four 16-bit files, addressed by a 2-bit register”. In my experience, when writing a similar microcontroller architecture (discussed later in this series), there is nothing convenient about further partitioning the small RAM address space into 16-word blocks, unless you are writing a 16-entry circular buffer. As with many design compromises, the microcontroller design team crammed the entire CPU along with RAM, ROM, and I/O circuitry onto an early semiconductor die, and I would bet that this particular design choice made the TMS1000 microcontroller hardware design simpler and smaller, trading the convenience of hardware design at the usual expense of programmer convenience.
Unlike the dedicated I/O design of the TMS0100 calculator chip family, the TMS1000 microcontroller has universal I/O pins, at least nominally. The four input pins (K1, K2, K4 and K8) can be read as a group using a single instruction. The output pins are more complex. The original TMS1000 microcontroller had 11 “R” outputs (R0 to R10) and 8 “O” outputs (O0 to O7). The “R” outputs are set and cleared separately. The “O” outputs are controlled by a mask-programmed PLA and are driven by a 5-bit latch. The four bits in the latch can be set by an instruction that moves data directly from the TMS1000 accumulator to the latch. The fifth output bit comes from the status latch of the ALU. The use of PLA to extend the 5-bit output latch to 8 output pins recalls the TMS1000’s heritage as a descendant of the calculator chip, which was designed to drive a 7-segment display.
Among Adam Osborne’s many accomplishments, he documented the early microprocessors and microcontrollers in his 1978 book, Introduction to Microcomputers. In his description of the TMS1000, Osborne seems more concerned with the limitations of microcontrollers:
“The fact that the TMS1000 family of minicomputers was a single-chip device had some minor, non-obvious implications. Most importantly, there is no such thing as a support device. 1024 or 2048 bytes of ROM [the TMS1200 microcontroller has 2Kbytes of ROM] represents the exact amount of program memory that will be present; no more and no less. Similarly, the 64 or 128 bytes of RAM (a byte is a 4-bit word) cannot be expanded. Direct memory access logic does not exist – and its existence makes little sense anyway; since the total amount of RAM and ROM available is small, there is simply no opportunity to transfer blocks of data for a long enough period of time to guarantee bypassing the CPU.
Similarly, the role of interrupts in the TMS1000 microcomputer is negligible. Considering the small amount of program memory storage available and the low cost of the package, it is difficult to justify the complexity of interrupting logic just to get the microcomputer to perform multiple tasks.”
In my opinion, Osborne’s words suggest that many people (probably including Osborne ) did not clearly understand the difference between microcontrollers and microprocessors when he published that book in 1978, four years after TI first announced the TMS1000 family. Many did understand the difference, however, because by 1979, TI was reportedly producing tens of millions of TMS1000 parts per year, and they were selling the TMS1000 in large quantities for $2 or $3. The low unit cost of the TMS1000 was possible, in part, because TI packaged the device in an inexpensive 28-pin plastic DIP.
TI has been eating its own dog food by using members of the TMS1000 microcontroller family in some of its own consumer products, including the legendary TI Speak & Spell game and the SR-16 “Electronic Calculator Ruler” calculator.
Inventor, game designer and “father of the home video game console” Ralph Baer realized he could make affordable video games with microcontrollers and integrated the TMS1000 into one of the most successful handheld video games of all time, Milton Bradley’s Simon, which was released in 1978. The game was launched in 1978. Today, everyone plays handheld games on their own cell phones, but back then, these games required specialized hardware.
A year after Parker Brothers released its TMS1000 microcontroller-based handheld video game Merlin in 1978, Milton Bradley used the TMS1000 microcontroller as the programmable brain for its Big Trak, a futuristic six-wheeled tank-like vehicle that could be pre-programmed to follow a specific path by a membrane keyboard embedded in the back of the toy. The Big Trak can execute a sequence of 16 commands entered into the keyboard, which appears to be similar to the Logo programming language developed in 1967 by Wally feurzeeig, Seymour Papert and Cynthia Solomon at a research company called Bolt, Beranek and Newman (BBN) in Cambridge, Massachusetts. The turtle graphics of the Logo programming language developed are closely related.
In 1977, Mattel introduced a highly successful electronic soccer game. The game was based on the Rockwell calculator chip, but companies around the world cloned the game, and a Hong Kong game manufacturer called Conic seems to have used TMS1000 microcontrollers instead of the calculator chip in its clone. The open source game simulator MAME (multi arcade emulator) can still run the TMS1000 ROM code for Conic’s Football in simulation.
In his book State of the Art, author Stan Augarten notes that the TMS1000 is used in calculators, toys, games, appliances, burglar alarms, copiers, and jukeboxes. Augarten concludes his description of the TMS1000 by writing, “Like any integrated circuit, the TMS1000 helped make the power of modern electronics available to everyone.”
I suspect that countless other undocumented TMS1000 family applications exist. For a second early family of microcontrollers, this is quite a success story and legacy, and a testament to the true ubiquity of the basic single-chip microcontroller concept. After TI introduced the TMS1000 in 1974, new microcontrollers from other semiconductor manufacturers came out at a rapid pace.
Now that we’re in the 21st century, most people rarely think about Rockwell Microelectronics’ connection to microprocessors and microcontrollers. The parent company, North American Rockwell (renamed Rockwell International in 1973), is a major military/aerospace contractor. Rockwell built the Apollo spacecraft, the B1 bomber and the U.S. space shuttle.
For a long time, most U.S. space booster rockets and intercontinental ballistic missiles used Rockwell’s Rocketdyne engines. 1972 saw the introduction of the world’s third commercially successful microprocessor, the 4-bit PPS-4. 1976 saw the release of Rockwell’s single-chip microcontroller based on the PPS-4 architecture. It was called the PPS-4/1.
As was the trend for many large conglomerates in the 1960s, Rockwell started its own semiconductor manufacturing business in 1967 in its Autometics Division. autometics developed a variety of military/aerospace avionics systems, including inertial navigation and guidance systems for U.S. submarines and intercontinental ballistic missiles, which created a demand for advanced semiconductors. North American Rockwell Microelectronics Corporation (NRMEC) developed early MOS/LSI process technology for its military and aerospace programs.
When Japan’s Sharp turned to a semiconductor supplier to build a calculator chipset of its own design, NRMEC’s MOS/LSI capabilities fit Sharp’s needs. The result of the collaboration was a quad-chip set that Sharp incorporated into its QT-8D calculator. Sharp released this calculator in August 1968. In fact, some might say that the Rockwell chipset in Sharp’s QT-8D calculator ushered in the MOS/LSI era. in 1970, Rockwell began publishing a catalog of MOS/LSI chips.
As Texas Instruments found with the TMS1000 microcontroller, it was a short jump from electronic calculator architecture to 4-bit microprocessors, or in the case of Texas Instruments (TI), to microcontrollers. Rockwell announced the 4-bit PPS-4 microprocessor family in August 1972. It was the third commercially successful microprocessor in the world, and its introduction followed Intel’s release of the 4-bit 4004 and 8-bit 8008 microprocessors. Rockwell’s “PPS” name means “Parallel Processing System”.
Two things set Rockwell’s PPS-4 microprocessor apart from its competitors. The first is Rockwell’s unique QUIP (Quad Inline Package) device package. Rockwell’s QUIP chips are easily identified by the interleaved leads. Because of their appearance, these chips are often referred to as “spiders”. The QUIP lead configuration makes it easier to design printed circuit boards for these devices in an era when the minimum board alignment and space is about 10 mils.
The second notable feature was the companion chip developed by Rockwell for the PPS-4 microprocessor. By 1975, the chipset family included the CPU, the clock generator/driver needed for Rockwell’s unique four-phase clock, 256 x 4-bit RAM, 1 and 2 kilobytes of ROM, a RAM/ROM combo chip, keyboard and display controller, printer controller, general-purpose I/O chip, and a 1200 bps analog modem. (The 1200 bps analog modem started a long line of modem chips that led to NRMEC becoming Conexant Systems, which was eventually acquired by Synaptics.)
The large number of chips in the Rockwell PPS-4 microprocessor family allowed the processor to be used in a wide range of end products, including cash registers, fax machines, home appliances, pinball machines, toys, and calculators. However, the market for the multi-chip, 4-bit microprocessor family was short-lived. Semiconductor technology was evolving rapidly and device densities were increasing at an alarming rate. in October 1975, Rockwell integrated a clock generator into the microprocessor and combined RAM, ROM, and I/O peripherals into a 2-chip set called the PPS-4/2, but the 2-chip set was also short-lived due to further advances in semiconductor process technology. in early 1976, Rockwell released the PPS-4/1, a true monolithic microcontroller based on the original PPS-4 microprocessor architecture.
There is little history of the Rockwell PPS-4 application on the Internet except for information about the PPS4-based calculator and a rather unusual application: the Gottlieb pinball machine. gottlieb contracted with Rockwell to develop a System 1 pinball controller board based on the PPS-4/2 microprocessor. Gottlieb used the System 1 board in pinball machines released from 1977 to 1980. The first pinball machine to use the System 1 board was called “Cleopatra”. Other microprocessor-based pinball games followed, such as Sinbad, Dragon, Charlie’s Angels, Incredible Hulk, Buck Rogers, and Totem. There are 16 pinball games in this series.
This is the kind of history that is easily forgotten by time, but the history of the PPS-4 as a pinball controller is not forgotten for two reasons. First, collectors rewarded Gottlieb pinball machines based on the Department System 1 boards. Second, the metal gates, MOS/LSI PPS-4 rom / peripheral chips on these boards are failing and they are now approaching half a century old. Typically, pinball collectors are trapped in end-of-life machines when these parts fail because they have not been produced for decades and the semiconductor supplier, NRMEC, is long gone.
Gottlieb contracted Rockwell to design a System 1 pinball controller board based on the PPS4/2 microprocessor chipset. Image credit:Stephen Emery, ChipScapes.com
The French consulting firm AA55 has developed a solution to this problem. The company has developed an FPGA-based Rockwell PPS-4 peripheral chip. the target for AA55 Consulting’s FPGA code appears to have been produced by AMD/Xilinx, as the project files were formatted for Xilinx’s ISE development software. AA55 Consulting has not yet reverse engineered the PPS-4/2 processor, but plans to to do so. Maybe next year.
Since Rockwell components are now almost pure unobtanium, NI-Wumpf in Honeoye Falls, NY, has developed a functional replacement for the original Gottlieb System 1 board and does not use any Rockwell Semiconductor boards. The original NI-Wumpf board appears to be based on the Zilog Z80 microprocessor. The latest version uses an STMicroelectronics STM32F103 microcontroller, which contains a 72 MHz Arm Cortex-M3 processor. For comparison, the PPS-4/2 microprocessor operates at 199 kHZ. a French company called Flippp! has taken a similar approach, developing board-level alternatives to the System 1 board known as the PI-1 and PI-1×4, designed and programmed by Pascal Janin. The board also seems to be based on more modern microcontrollers.
It is interesting to read some of the reviews from users of the Gottlieb pinball machines based on the System 1 board. Most people consider Rockwell to be strictly a defense contractor only. A site called pinwebsite has a forum dedicated to Gottlieb and one of the topics is “Why is Gottlieb’s System 1 so bad?” Here are some quotes from that thread:
“At the time, Rockwell seemed like a good choice. After all, they designed computer equipment for NASA and the Department of Defense, so what could go wrong? Apparently, there was a lot. Rockwell decided to make questionable decisions about grounding, using custom-designed components and other weird stuff that really screwed up Gottlieb.”
“Why would Rockwell spend extra time and effort designing custom spider chips when they still aren’t as good as the off-the-shelf 68xx chips that William and Bally use?” Using custom hardware hardly seems like a cost savings for them.”
Gottlieb was not aware of this and made some poor choices in the outsourcing process. As for Rockwell, you might wonder what the bigger miracle is:Did the pinball machine work, or did their NASA product work?”
I think Rockwell used parts that were “off the shelf” for them for the spider. Part of the problem may be that they never designed the hardware for the environment in which the pinball game is played. Expect the switch to go wrong when it flips on, not bang off? Isn’t hardware “off the shelf” for anyone outside the defense industry?
If I wanted to hire a company to design some electronics for me, even if Rockwell had a good name, I wouldn’t want to hire a company that’s used to doing government projects,” I said. In most cases, they are bloated, expensive, and over-engineered. I’m not sure that was the case in the late 70s, but just because a space device works well doesn’t mean it’s not overpriced and overdesigned.”
“Rockwell designed the system as a 4-bit system – which was obsolete before it was released.”
No doubt people who collect pinball machines as a hobby today don’t know that Rockwell was a commercial chip supplier in the 1970s, that the PPS-4 has a long history, that there was a need for a 4-bit microprocessor and microcontroller, that Rockwell developed the “Spider” QUIP, or that poorly maintained systems have failed for half a century. know that half a century of poorly maintained systems often fail. However, some collectors are well-informed. For example:
“On the electronics side – System 1 uses technology from the mid-1970s. All of the electronics are off-the-shelf components, no custom components. In fact, Rockwell used their own components – and who can blame them? I see only two drawbacks to it-poor grounding techniques and edge connectors.
“As for their CPUs being unpopular-they were very popular at point-of-sale terminals for quite some time. But when MOS Technology introduced the affordable 6502 series processors, their 4-bit processors went out of business.”
Rockwell Microelectronics and the PPS-4 product line have also disappeared from the collective memory of those actively involved in the electronics industry, and it’s hard to find a history of the PPS-4 online. You almost need to resort to old books. Fortunately, I have some of these books on the shelves in my study.
For example, the 1981 edition of the Osborne 4 & 8-bit Microprocessor Handbook lists 10 members of the Rockwell PPS-4/1 microcontroller family. Family members had 640 to 2048 bytes of ROM and 48 to 128 4-bit RAM. all but one family member had three integrated serial I/O ports, which were really nothing more than serial 4-bit shift registers. the MM76C was a family member with a high-speed upstream/downstream timer/counter subsystem that could operate as a 16-bit counter or two 8 counter. The counter can also handle the quadrature encoded inputs used by optical encoders. The timer/counter subsystem opens up additional industrial applications for the Rockwell PPS-4/1 microcontroller, including motor control, frequency counting, analog-to-digital conversion, and frequency synthesis.
If you’re not familiar with NRMEC, Rockwell Microelectronics or Rockwell Semiconductor, it’s probably because the company was spun off as Conexant Systems in 1999 as part of a worldwide effort to push the value of internally held semiconductor companies into the stock market. Conexant spun off its fab (formerly Rockwell’s fab) in 2002 into Jazz Semiconductor and has since gone fabless. tower Semiconductor acquired Jazz Semiconductor in 2008 and became TowerJazz. the company reverted to the Tower Semiconductor name in 2020 and now Intel is acquiring The company. Meanwhile, Rockwell’s early MOS/LSI processes are gone and mostly forgotten.
