January 19, 2006 -- The number of options for choosing the best processor for embedded-system designs continues to increase. In addition to microprocessors, microcontrollers, and DSPs (digital-signal processors), several unified microprocessors from companies such as Analog Devices, Infineon, Microchip, and Freescale have also emerged. These software-programmable devices offer unified-processor architectures that combine features of microcontrollers and DSPs to better mix control and signal processing in a single instruction engine. More recently, new silicon products and more mature tools are available to embedded-system designers to better harness the power of programmable logic as custom accelerators of software algorithms for signal processing.

The increasing incorporation of digital-signal processing in electronic applications has led over the years to a number of claims and predictions by competing semiconductor providers. One claim is that, for applications with high computational loads, FPGAs are better than DSPs for digital-signal processing and that designers can eliminate the need for DSPs in their designs by adding processor cores in the FPGA. A similar claim for applications that require some signal processing states that a microprocessor architecture that incorporates integrated digital-signal-processing extensions can replace DSPs.

Claims such as these could suggest that FPGAs are encroaching on the domain of DSPs from the computational high end and hybrid microprocessors from the computational low end. However, the replacement of DSPs in embedded-system designs by FPGAs and unified microprocessors is analogous to the bid of 32-bit processors to replace 8-bit processors. In other words, embedded-system designs are not eliminating the use of DSPs; for analogous reasons, 8- or even 4-bit processors have not become extinct. In fact, the message among semiconductor vendors has been making an important shift over the previous year or two from a position of compete and replace to a stance of coexist and complement. This recent shift is most visible among suppliers of DSPs and FPGAs.

By Robert Cravotta, EDN Technical Editor