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Microcontroller vendors further encroach on SOCs

By Ron Wilson, Executive Editor -- EDN, 3/3/2006

As the markets for handheld and automotive-media players expand, vendors of high-end microcontrollers are smelling opportunity that in the past might have gone automatically to OEM-designed SOCs (systems on chips). A recent case in point is the Renesas SH7785 (block diagram), a member of the venerable SH microcontroller family. The 7785 illustrates a number of points about this still-emerging market. One is the ability of advanced microcontrollers to meet needs in processing power, media-handling, and peripheral richness that would appear to demand an SOC. Another, closely related point is the shift of media-processing functions from hardware accelerators to software as CPUs become more powerful. And a third point is the growing segmentation of just the automotive-infotainment, or CIS (car-information-system), market.

Renesas based the 7785 on a 600-MHz implementation of the SH processor core—enabling the chip to execute SIMD (single-instruction-multiple-data) media-processing instructions at a high instruction rate. This features combines with expansion of the on-chip RAM to 24 kbytes of instruction RAM and 128 kbytes of user data RAM, permitting media applications to operate with minimal support from hardware accelerators, freeing silicon either for more interface diversity or for smaller die.

According to Renesas Segment Marketing Manager Paul Sykes, the chip can execute real-time software decoding of either MPEG 2 or h.264 video streams. The only hardware assistance, other than the SIMD unit now familiar to SH users, is a motion-compensation engine in the on-chip graphics controller. This unit also assists in such pixel-translation tasks as smoothly moving a map across the screen in car-navigation applications.

The decision to implement a faster core and not a 2- or 3-D graphics pipeline reflects a growing segmentation Renesas sees in the CIS market, according to Sykes. In the United States, in-car displays tend to be either 2-D maps or videos. For those systems, this chip gives an excellent combination of die size and performance. In Japan, navigation displays tend to use moving 3-D images that render buildings and scenery rather than flat maps. For those systems, Renesas sees more interest in the SH777x family, which includes a 3-D-rendering engine on the die.

Similarly, as CIS systems move from afterthoughts to integral parts of an automobile design, the microcontroller must evolve from an application processor to a central processor. This move demands a greater diversity of peripherals, including CANbus interfaces and, as these systems increase their data storage demands, storage interfaces, as well.

Also along this path, displays become higher resolution and more complex, making their own new demands. Displays will not only force a move to high-speed serial-display ports, but also may impose new ideas in system partitioning. Noel Giamello, senior business director at Sharp Microelectronics , can’t wait to see that happen. Sharp, with a dominant position in the flat-panel-display market, sees the world dropping into its palm. Giamello explains that not only is Sharp seeing not only a move toward advanced serial-display interfaces—with obvious implications for the microcontroller—but also increasing interest on circuit-on-glass technology to physically mount the display controller on the panel. This approach changes the whole partitioning of the system, moving the render-ing functions and its attendant memory off the microcontroller and demanding a high-speed command-and-data interface between the microcontroller and the panel.

Both vendors see the evolution of what had been a microcontroller business into something that looks much more like the systems business. The product now, they report, is not a chip. It is a subsystem with interfaces, supporting electronics, board layouts, compliance and environmental testing, operating systems, middleware, and even some application code. As more functions move into software, the chip at the heart of this system becomes more and more standard—and more and more subject to the vast economies of scale of the microcontroller world.