Electronic Design

Microcontrollers

Microcontrollers run the gamut from tiny 4-bit processors to 64-bit powerhouses. Unfortunately, space limitations don't allow the table to do justice to the extensive product lines that most vendors have, so check out their Web sites. Each family may have dozens of versions with different peripherals, pinouts, and packaging. Likewise, various versions can incorporate ROM, one-time programming PROM, EEPROM, or flash memory for program storage.

Flash-based MCU demand has been steadily increasing at the expense of OTP- and ROM-based MCUs. This is due to improvements in flash memory's power consumption and performance. The flexibility it provides is far superior to the alternatives. Programming times are significantly lower than with earlier products, and self-programming is a key feature.

The table covers most of the microcontroller arena, including multichip modules that contain a processor or MCU plus flash and RAM. It also is possible to get custom multichip modules from a number of sources.

But the table excludes coverage of MCU-like devices, such as NetSilicon's NET+ARM and National Semiconductor's Geode GX2. These devices incorporate all of the peripherals, and some products even incorporate flash memory, but RAM is normally off-chip. This enables systems to be built with large amounts of memory.

Low-Cost Development Kits Make MCU Evaluation A Snap
MCUs are inexpensive by design, ranging from free to a few hundred dollars. Most of the development kits available from the manufacturers and third parties are cheap too. This provides developers with an opportunity to see whether an MCU meets their needs, or if another alternative should be tried.

The development tools provided with these kits vary a great deal. Usually, an assembler is part of the basic complement of tools, although some products support high-level languages. For example, Rabbit's line of processors runs Dynamic C. Systronix's J-Stamp and Parallax's Javelin Stamp run only Java. But some other products come with high-level language support. For example, Motorola's Nitron HC08 development kit comes with Metrowerks' CodeWarrior C compiler.

RTOS support is available for most MCUs, but many applications don't require the sophistication of an RTOS. This is especially true for 4- and 8-bit solutions. However, things are changing as memory capacity and processor performance increase. CMX Systems (www.cmx.com) is just one RTOS vendor that supports the 8- and 16-bit RTOS space.

Many developers can get along with the tools in these low-cost kits, but many will still want to employ the more expensive emulators and ICE units like those available from Nohau (www.nohau.com) Corp. ICE still has the edge in debugging.

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