ARCHITECTURES: MCUs bulk up for tasks once handled by ASSPs

by Ron Wilson, EE Times
(11/21/2005 9:00 AM EST)
 
With a careful choice of peripherals and an eye toward an inexpensive companion chip — or perhaps a small FPGA or structured ASIC to meet specific peripheral needs — a standard-product microcontroller can be turned into a formidable applications engine. Such a device blurs what used to be a simple distinction between MCUs and application-specific standard products (ASSPs), devices equipped with powerful RISC cores, application accelerators and application-specific peripherals, all tuned to the needs of a particular set of vertical markets.

The spiraling cost of ASIC development and the difficulty of adapting an ASSP to a use even slightly different from that conceived by the original chip designers is proving difficult and expensive. Enter the lowly microcontroller. With modern processes, substantial processors and significant amounts of local RAM, it can climb on a die that can sell in the MCU price range.

One indication of this trend is Atmel Corp.'s announcement last week of a new line of 200-Mips ARM9-based MCU chips. Not only is the MCU fast by embedded standards, but the SAM9 family's internal architecture is much more closely related to purpose-built high-end ASSPs than it is to traditional MCUs.

Like any MCU, the AT91SAM9261 — the first member of the family — offers a CPU core, on-chip memory and general-purpose control and communications peripherals. Like many other MCUs, it has a radically low-power shutdown mode with hardware provisions for getting in and out.

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