Markus Levy, Technical Editor,
and James P Leonard, Senior Associate Editor
Markus Levy, Technical Editor,
and James P Leonard, Senior Associate Editor
At last, here at your fingertips, is EDN's new-and-improved, largest-ever, 22nd annual microprocessor/microcontroller directory. This time around, we've taken a very different approach to presenting architectural and design information: We've compiled a set of comparison tables that provides a comprehensive run-down of the specs and features for the most frequently specified processors currently available on the market.
The primary goal of this directory is to deliver concise, up-to-date, and accurate information on the spectrum of µPs and µCs available today. To accomplish this goal, we've divided the directory into two sections: text write-ups and comparison tables. The text sections contain processor theory. You'll find architectural descriptions and overviews for 45 µP/µC families. In a new quick-read format, these sections are handy if you're curious about how the devices are put together or need current information on register and instruction sets, pipeline stages, or power-management features. The directory divides into four sections: Chips are grouped into their respective 8-, 16-, 32-, and 64-bit sections.
The comprehensive comparison tables provide practical information. Review the tables when you need a processor for your next design. They contain information on a processor's operational and performance characteristics, system interface (including bus width and packaging), on-chip memory and peripherals, and price--which is, in many cases, the most difficult (but crucial) piece of information to extract from vendors.
To get the most out of these tables, take a minute to review some of the assumptions we've made in compiling such vast amounts of specs and technical information:
Address range: For µCs without an external bus (on-chip memory only), assume these numbers imply the most memory (EPROM, ROM, etc) that can be stuffed into the chip. For devices with an external bus, the address-range category is typically based on the number of address pins a device has, although some of the devices with built-in MMUs can perform virtual-to-physical address translations and are, therefore, not pin-limited. Some processors, such as the 8051, have separate instruction and data spaces, which is notated as 64/64 in the table.
Data bus width: This category represents the internal and external data paths. The listing for a processor with a 64-bit external bus and a 32-bit internal bus, for example, reads 64/32. However, if this same processor accommodates variable external memory widths (as many do) the bus widths may read as 64/(8, 16, or 32).
Hardware multiplier: This category refers to an on-chip multiplier that is separate from a chip's FPU (if present), meaning that there is a dedicated piece of silicon that performs fast multiply (typically single-cycle) and (sometimes) divide operations.
Maximum CPU frequency: Rather than including a range of operating frequencies, this category lists a processor's fastest speed. You can safely assume that vendors offer slower speeds for most of their devices.
Maximum interrupt latency: This category is most useful for 8- and 16-bit µPs and µCs, devices that are designed to handle time-critical interrupt processing. But, for high-end devices such as Intel's Pentium and Sun's UltraSPARC, it's difficult to list a spec in this category because of the variety of runtime permutations.
Operating voltage: Many devices operate at dual voltages, typically 3.3 and 5V. But, although not indicated in the tables, many processors that run only at 3.3V have 5V-tolerant I/O.
Power management: Most devices include some form of power management, although some chips reduce power only by lowering the clock frequency. Generally, the numbers in this category represent the current consumed during the corresponding power-management mode with the processor running at the maximum CPU frequency.
Manufacturer's suggested retail price (MSRP): µP/µC prices fluctuate as frequently as the stock market, so prices may vary slightly by the time you read this.
Enough explanation. We're sure you're chomping at the bit to dig into this directory, so have fun.