Copyright Ó 2001 Microcontroller.com. All Rights Reserved.
Contact Microcontroller.com for reprint and copy permission
business is, at its base, a real estate business where the cost is about $300 million per
acre! Faster execution is also part of the selection criteria, but it is more important now
than before. By contrast, the benefits of DSP hardware result in faster execution speed
and improved data throughput. Code size has traditionally not been as significant as
execution speed in digital signal processing, but this too is changing (more on this later).
Control-oriented systems have traditionally utilized only microcontrollers. Some
embedded applications added a DSP accessible to the microcontroller's memory space
to speed processing of math-oriented tasks. Examples include:
Digital motor control,
Hard disk controllers,
Feature phones, and
These systems are primarily control-oriented, with the DSP acting as a math co-
processor to the microcontroller.
In other applications, the microcontroller and the DSP shared the load equally in
managing different parts of the system. This has typically been seen in high-growth
segments such as some communications and telephony applications. Note that "high-
growth" in embedded systems is usually synonymous for "cost sensitive"!
CHOOSING EMBEDDED CORES FOR STANDARD APPLICATIONS
Microcontrollers in deeply embedded applications (no external memory) have typically
been chosen for their cost-effectiveness. Besides the cost of the product, factors that
contribute to cost-effectiveness are:
Features related to code efficiency and
The on-chip integration of hardware peripherals.
In the past, DSP architectures had been chosen primarily for throughput and raw
computational power. On-chip peripherals would have gone unused. A priority-based
interrupt structure and other real-time control features were not included because real-
time control could interfere with the critical processing of time-sensitive data.
Microcontroller applications didn't require a DSP's expensive performance
enhancements. Each system was different, and the microcontroller and DSP were seen
as two different animals.
The times, they are a-changin'.