ABSTRACT
Embedded-system design and microprocessor history form a closely linked double helix. Without microprocessors, there would be no embedded systems because the very term “embedded” refers to the microprocessor(s) embedded inside of some electronic system that is clearly not a computer. Microprocessors coupled with software or firmware allow system complexity with flexibility in ways not possible before microprocessors existed. No other digital building block can as easily manage a windowed user interface or compute a complicated mathematical algorithm as software or firmware running on a processor. The numerous limitations of the earliest microprocessors-including lim-
ited address spaces, narrow data buses, primitive stacks (or no stacks at all), and slow processing speeds-made them poor foundations for designing computer systems but designers have used microprocessors since their introduction to build increasingly complex embedded systems. Because
12-2 Embedded Systems Design and Verification
of their complexity, such systems would be impractical or impossible to make without the nimble firmware adaptability inherent in microprocessor-based design.
