Mark Twain once quipped, “Reports of my demise have been greatly exaggerated.” The same can probably be said of the often expressed idea that 8-bit microcontrollers are in decline. The reality appears to be that despite the competition from low-cost, low-power 32-bit MCUs, 8-bit MCUs are not only holding their own in the embedded market race, they are getting their second wind.

It's easy to see why one might think that 8-bit MCUs are a dying breed. The pace of technology advance has conditioned us to believe that anything more than a half-decade old has been rendered obsolete and that in a few more years will become unavailable as vendors turn their production resources over to newer products. Further, 32-bit processors have been dropping in price and have become available in sizes that rival that of 8-bit MCUs, reducing those former 8-bit advantages. We thus expect 8-bit processing to fade away.

There is data to support this expectation. The annual embedded market study that UBM (EDN's parent company) conducts has survey results showing a steady trend over the last five years: 8-bit and 16-bit MCU use is declining while 32-bit is on the rise.

But as has been pointed out to me by Microchip and other champions of 8-bit processing, these ideas and expectations miss a key point: embedded designs are not always based on a single processor. There are many benefits to splitting off some kinds of functionality into smaller, autonomous processors to simplify the design and operation of applications programs. Why compound the difficulty of handling a critical industrial control task, for instance, by burdening the central processor with the petty details of handling a display system at the same time? Carve out the user IO task and give it to another processor to handle.
 
These 8-bit champions make a good point. While 32-bit use is on the rise, so is multiple processor design, and 8-bit use there may not be getting the recognition it deserves. Even the UBM survey would miss 8-bit use. The survey question asks “What was the main processor you used in your most recent design?” (emphasis added). This completely ignores the question of what secondary processors a design may contain. It has also been pointed out to me that 8-bit designs tend to be completed more quickly than 32-bit designs, and the question only asks about the most recent project, not how many projects they completed this year.

There have also been a couple of things that show me 8-bit design is in growth mode rather than decline.