EDNE December 2012 - (Page 29)

the continually posed question about the pending death of the 8-bit processor. Four-bit processors reside at the bottom-left corner of the sweet-spot spectrum (Figure 2), and they are explicitly included because companies are still making 4-bit processors in quantity, despite the lack of public marketing from vendors and users. In fact, companies involved in the 4-bit market appear reluctant to reveal much, presumably for competitive reasons; but I have teased out some non-intuitive, useful insights about the market through informal conversations with participants. These companies do not sell their 4-bit processors to the public developer community in the same way that participants in the market for 8-, 16-, and 32-bit processors generally sell their offerings. Like the semiconductor companies that produce processors at the bleeding edge of technology (along the rightmost edge of the spectrum), 4-bit processor providers actively seek out and identify the designers that can best make use of their processors—not the other way around. A 4-bit processor provider approaches a potential developer and works out specific implementation details to demonstrate how its 4-bit device can provide differentiation to the developer’s design and end product. Four-bit processors are manufactured only for dedicated high-volume products. Some, if not all, 4-bit processors are available only as ROM-based devices. To accommodate the high labor intensity of verifying the mask sets, vendors of such devices limit the number of engaged customers to those who will consume very large quantities. Further, 4-bit processors are programmed in assembly language only. The software development tools cost in the range of $10,000, and, at least according to the company that shared its information with me, the vendor lends the development tools to its clients; it does not sell the tools. The sweet spot for 4-bit processor designs is single-battery applications for which the typical life span is 10 years and the device is active perhaps 1% of that time, spending the other 99% in standby mode. An interesting differentiator for 4-bit processors is that they can operate at 0.6V; this provides an energy-consumption advantage over even 8-bit processors. Also, 4-bit processors have been supporting energy-harvesting designs since 1990, whereas 8-, 16-, and 32-bit processor vendors have started offering development and demonstration kits only within the past few years. Strive for riGhtSiziNG We have already stipulated that we are looking at a 32-bit microcontroller that has reached price and energy-performance parity with an 8-bit microcontroller or has even surpassed it on those parameters. How is this possible? Let’s tackle price first. The 32-bit device is manufactured in a state-of-the-art process geometry, whereas the 8-bit device is manufactured in a much larger process node but in a fully depreciated facility. Even though the buses in the 32-bit core are four times as wide, the relative area of silicon each CPU consumes approaches parity as the distance between the two process nodes increases. Additionally, in larger devices, the core itself represents a diminishing share of the silicon; the memory and peripherals consume the vast majority of the www.edn-europe.com december 2012 | EDN EUROPE 29 http://digikey.com/europe http://www.edn-europe.com

Table of Contents for the Digital Edition of EDNE December 2012

Cover
Contents
Texas Instruments Europe
Microchip
Digi-Key
Masthead
EDN comment
Pulse
Digi-Key
Baker’s Best
Embedded World 2013
Test & Measurement World
Rohde & Schwarz
Digi-Key
Squeezing the most from battery cells with a switched-mode pump
Signal integrity
Processor architectures : one to rule them all ?
Digi-Key
Mechatronics in Design
Advances in wireless speaker performance and technology
Design Ideas
Teardown; the ultimate Consumer Product ?
Product roundup
Tales from the Cube

EDNE December 2012