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8bit MCUs remains the industry's workhorse

Posted: 01 Apr 2008     Print Version  Bookmark and Share

Keywords:microcontroller  workhorse MCU  8bit MCU  flash data memory  ASICs 

The new generations of super-powered processors get all the attention, but the humble 8bit MCU remains the industry's workhorse. Even as feature creep moves some applications to 16bit and beyond, continual increases in the processing capabilities and integration levels of 8bit devices are opening new applications. The result is an expanding array of increasingly powerful 8bit MCUs for cost-conscious designs.

Against the dazzle and fanfare associated with advances in high-end processor power, quiet, incremental improvements at the low end can seem pale in comparison. A recent announcement from Microchip Technology Inc., for instance, heralded a new line of its PIC 8bit MCUs&$8212;the eight-pin PIC12F519 and the 14-pin PIC16F526—featuring 64bytes of on-board flash data memory. That addition may not represent a major technological leap, but it is representative of a trend of continual improvement in 8bit MCU units that is having a cumulative impact.


'Incremental innovation'"The history of the 8bit space has been one of incremental innovation," said Sanie Duvenhage, Microchip product marketing applications manager. "They are becoming more compact, lowering in cost and achieving significant steps up in capability and flexibility."

Architectural improvements like the single-clock instructions of Toshiba's latest 8bit devices are helping the controller category stay ahead of demand for more features.

Toshiba America Inc.'s business development manager, David Chen, agrees. "Customers now expect higher integration, more features and peripherals, and faster performance, all at the same or lower cost," he explained. As a result, 8bit MCUs now routinely contain serial and parallel digital I/O, ADCs and DACs, timers, oscillators, non-volatile memory and a host of other capabilities.

The exact mix of functions available varies widely, however, driven by diverse application needs. "Typical high-end processor development models target big applications," said Duvenhage, "but the 8bit market is fragmented and horizontal." Microchip reports that the top 10 of its nearly 60,000 customers account for less than 10 percent of its business.

One result is tremendous diversity in the mix of memory, peripherals, I/O and system functions in any given MCU family. Vendors such as STMicroelectronics NV, for instance, list hundreds of 8bit MCUs in their catalogs.

Another result is the proliferation of 8bit MCU design wins. According to Gartner Dataquest, 8bit controllers account for more than half of the processor market by volume. That dominance appears to be remaining stable—and may in fact be growing—with 8bit MCUs staying one step ahead of increasing demand for more system features and lower prices from 16bit and 32bit competitors.

This result seems counterintuitive; lower costs of higher-performing alternatives should trigger a migration away from 8bit devices. In some cases, such migration has occurred. Kevin Belnap, marketing manager for Texas Instruments Inc.'s MSP430 16bit MCU group, noted that "performance is part of what defines the break between the 8bit and 16bit markets." Belnap pointed out that rising performance demands in some applications create a need for double-precision computation or 16bit analog, while 16bit MCUs are following costs down with each new semiconductor process generation.

New apps replace old
There are compensating factors at work, however. The process advances that are lowering the cost of 16bit devices are also boosting performance in 8bitters. Architectural improvements are also bolstering performance. Toshiba America, for instance, last year introduced a family of 8bit MCUs based on its TLCS-870/C1 core that offers single-clock execution of instructions. This marked a significant performance increase over architectures that require as many as four clocks per instruction. Such advances are helping 8bit MCUs retain their hold on many applications.

Higher integration is yet another factor making 8bit MCUs attractive in applications that formerly used ASICs, programmable logic or non-electronic approaches. With 8bit MCUs now available for mere pennies, devices such as battery chargers, electric toothbrushes, coffee machines, home pregnancy test kits, toys and even fireworks now contain MCUs.

Microchip's new 8bit devices pack 64bytes of flash, reflecting a trend of incremental advances among workhorse MCUs.

Complex systems might even incorporate an 8bit MCU for some simple functions. Duvenhage, for instance, reported that engineers are using six-pin MCUs to control reset circuits that need a configurable time delay in different applications, simply because they are easy to configure and are less expensive than searching for and stocking the right discrete components. The result is that applications for 8bit MCUs are increasing as fast as or faster than larger MCUs can usurp them. "It kind of balances out," said Duvenhage. "The overall market is stable and will be for a long time."

Whole-cost equation
Pricing is key to capturing the new 8bit applications. "The 8bit world is basically about cost, cost, cost," said Chen. "The controllers need to be priced very carefully in order to compete."

But component price alone is not the answer, Chen added. Vendors need to address the whole cost to the customer, including any savings in other areas that the MCU enables. For instance, the inclusion of a power-up reset circuit on the MCU eliminates the need for several external components, and customers take note of such benefits in their decision making.

To capitalize on such synergy, large companies such as Toshiba concentrate their marketing efforts on applications where they can offer customers a package deal that includes the MCU and several other system components at a combined price. Other companies, such as Microchip, aim to provide as much as possible on-chip while keeping prices low.

Another cost element that virtually all 8bit vendors are addressing is the customer's development cost. Low-cost and easy-to-use tools are now standard elements of the vendor's MCU offerings, along with extensive applications support. This need for support helps account for the diversity in 8bit offerings.

- Richard Quinnell
EE Times





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