The year Intel rolled out its first 8-bit microprocessor, Apollo 17 landed on the Moon. The Volkswagen Beetle became the best-selling car in history, surpassing the Ford Model T. And “The Godfather” was the world’s number-one movie.
So by now you might expect the electronics world to have moved beyond 8-bit devices. But like “The Godfather,” 8-bit keeps offering what engineers can’t refuse. “It’s not that it’s just hanging around,” noted Wayne Freeman, product marketing manager for Microchip Technology Inc., a major 8-bit MCU manufacturer. “It’s still the largest MCU market by revenue.”
Indeed, in 2014 -- 42 years after Intel’s rollout of the 8008 -- the godfather of microcontrollers accounted for 39.7% of overall sales revenues in the MCU market, according to Gartner Inc.’s “Market Share Analysis: Microcontrollers, Worldwide 2014.” That’s more than 32-bit devices (38.5%) and 16-bitters (21.8%), which grabbed most of the headlines.
In an industry where five years represent an eternity, why is an ancient technology so appealing to engineers building state-of-the-art products?
The answer is that 8-bit’s success has little to do with it being, well, 8 bits. For many engineers, it’s about familiarity. That’s why white goods makers employ 8-bit MCUs in refrigerators, freezers, washing machines, dryers, and dishwashers. It’s why automakers use it in window lifts, door locks, mirrors, seat motors, and interior lighting. It’s why tens of millions of smart cards incorporate them, and why countless low-end motors are controlled by them.
“It’s about legacy,” Jim McGregor, founder and principal analyst for Tirias Research, told Design News. “The engineers have been using it so long that they just don’t want to switch their software base.”
Click here to view Table 1.
It’s also about semiconductor makers’ willingness to surround 8-bit devices with more powerful platforms. Many engineers are making their choices based on pin count and flash memory, rather than on bit size, they say.
“We’re seeing developers choose it for up to about 32K (flash) and 32 pins,” said Andreas Eieland, director of marketing for Atmel Corp., a maker of 8-bit MCUs. “Above 32 pins and 32K, there’s a trend toward selecting something else, like a Cortex-M.”
Still-Growing Application Base
The single key to 8-bit’s ongoing success, however, may lie in its ability to integrate new functions. That’s why 8-bit not only survives, it posts modest growth.
Microchip, for example, continues to find new applications for its 8-bit devices. In July, the semiconductor maker rolled out four new members of its PIC16F1579 family, which includes devices that offer up to 28KB of flash, as well as packages of 14 to 20 pins. It also introduced the new PIC16F18877 family of 8-bitters, which are available in packages of up to 40 pins and 56KB of flash and are targeted at consumer electronics and Internet of Things applications.
Microchip’s engineers say the new devices are opening the door to a broader set of LED applications, as well. By incorporating a growing set of core-independent peripherals, the company’s new 8-bit devices have been used to drive a string of 160 WS2812 RGB LEDs. Such applications have generally not been considered candidates for 8-bit control up to now.
“We’ve got quite a few parts in our 8-bit arsenal that can drive high-power LEDs in closed-loop fashion from the peripherals, instead of from the core,” said Janmichael Aberouette, product marketing manager for Microchip.
Microchip says it has even made inroads with 8-bit devices in automotive engine control. The company has recently been working with a low-cost automaker in the Far East on use of an 8-bit MCU for internal combustion spark timing.
“We know that an 8-bit can’t do emissions control,” noted Freeman of Microchip. “You need more processing power for that. But if you just need to drive the spark plugs, it’s an almost perfect solution.”
Click here to view Table 2.
Similarly, Atmel is rolling out a host of new peripherals in its megaAVR family. The additions include peripheral touch controls, USB and LCD controls, and CAN and LIN controllers for automakers. Arduino employs 8-bit Atmel AVR MCUs in its open-source kits, and a growing number of IoT systems are using the technology to transmit data to the Internet.
Atmel says 8-bit technology simplifies product designs and reduces bill-of-material costs. “Especially below 32KB, 8-bit is still going to be cheaper for revenue reasons,” Eieland said.
No End in Sight
To be sure, some applications are moving away from 8-bit. In its study, Gartner noted that 16-bit devices are growing at 7% per year and 32-bit devices are expanding at 10% per year, while 8-bit has 0.7% annual growth. In the auto industry, most CAN- and Flexray-based applications are too advanced for 8-bit. Similarly, many IoT devices and advanced motor control applications lie outside the realm of 8 bits. In general, arithmetically intense applications tend to be solved with more powerful processing cores.
“The more you try to do, the more the higher-level MCUs become appealing,” noted McGregor of Tirias.
Still, many big semiconductor makers continue to support 8-bit production. Microchip, Atmel, Renesas, NXP, STMicroelectronics, and Freescale are part of a market that produced more than $6.2 billion in 8-bit MCUs last year. And experts say there’s no end in sight for the venerable technology.
“In some applications, 8-bit will still do the trick,” Eieland said, “even ten years from now.”
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Senior technical editor Chuck Murray has been writing about technology for 31 years. He joined Design News in 1987, and has covered electronics, automation, fluid power, and autos.