By: Jonah McLeod, Kilopass Technology Inc.
The widespread deployment of MEMS in smart phones has ancillary benefits that I thought worth looking into. One of these was breathing new life into 8-bit processors. I began my search by calling Hal Barbour. He’s the CEO of CAST, Inc. a company that has made a business offering a range of popular and standards-based IP cores including the venerable 8051. His COO, Nikos Zervas, joined the call as well.
The question I had for the two of them was the roll that the 8051 had in the development of the smart sensors going into smart phones, automobiles and Internet of Things. I picked the 8051 because of my past association with the processor while at my old company ARC International. One of the growing markets for ARC was in 8051 replacements and one of the company’s successes was displacing the 8051 in USB drive controllers.
The old saying that as one door closes another one opens appeared to be working for the 8051. As the CPU was designed out of the USB applications it began being integrated with smart sensors in a multichip package. The automotive tire pressure sensor was an example. Mandated by law to be included on new vehicles, all car models produced after September 2007 came with the tire pressure sensor. Many of the sensors came with the 8051, for example the Texas Instruments TPIC82000 Series. The electric utility power meter was another application adopting the 8051.
Hal pointed out that many of the sensor designs that began adopting the 8051 were being fabricated in the older processes, 130nm and larger. At these process nodes, gate count matters and the relative small size of the 8051 is a desired feature.
The continuing attraction to this simple 8-bit processor is borne out by market research data. The last market research on 8-bit processors I was able to find was published 2008 and it showed the 8051 with a declining 19 percent of the embedded processor market, still the largest share of all the 8-bit processors featured in the report. A recent IC Insights research bulletin published August 13 showed embedded processor in general growing; accounting for 11 percent of MPU sales in 2013 (versus 9 percent previously).
Hal and Nikos had a laundry list of reasons why the 8051 has remained popular since its formal introduction in 1980 beginning with cost. Unlike 32-bit processors that come with a license fee and royalty stream, the 8051 can be had for one upfront charge. And like the popular 32-bit architectures, the 8051 has a wide and deep ecosystem of software, programmer familiarity, and design expertise that make it and ideal solution for a wide range of embedded computing tasks.
Next, the two cited the fact that most of the engineers building sensors are analog and mixed signal designers. Their designs need more than a state machine to control analog mixed signal circuits and the 8051 fits the bill. The 8-bit microcontroller core also comes with the interfaces—Philips’ I2C, Motorola’s SPI, Bosch’s CAN buses—to connect analog-to-digital and digital-to-analog converters as well as other peripherals. To support remote sensors, the 8051 comes with circuits and stacks for wireless communications protocols: Zigbee, WiFi, BlueTooth, as well as Ethernet.
I asked Hal when the 8051 would reach the end of the road. He said he had thought the 8-bit workhorse was reaching its end six or seven years ago. In anticipation, he had begun adding 32-bit CPU IP to CAST’s product offering. But as history has demonstrated, the 8051 kept on going. Today though there are signs it may be loosing out to 32-bit alternatives.
Nikos pointed out that the applications that are migrating to more functionality are leaving the 8051 behind. If the data being processed comes in 8- or 16-bit resolution, simple sensors detecting on or off conditions or non-critical temperature and pressure readings, for example, then the area and power is competitive with a 32-bit solution, which might be overkill. If the data requires 32-bit resolution, such as being demanded in smart phone applications with their 6-, 9-, and now 10-degrees of freedom inertial measurement units, then 32-bit processors win hands down.
However, just as new applications came in to save the venerable 8-bit processor before, Internet of Things may yet hold some salvation for the 8051 going forward. It may find service as a controller in home monitoring systems providing WiFi, BlueTooth, and Zigbee protocol processing for communications to a central controller. Nikos says that these are the applications that the 8051 perform well. The growth of disposable sensors in medical and home health care applications could be another area of growth for the 8-bit engine.