23-10-2014, 04:03 PM
Computers as
Components
Principles of Embedded
Computing System Design
1408168810-PrinciplesofEmbeddedComputerSystemDesign.pdf (Size: 2.16 MB / Downloads: 23)
Embedded Computing
■ Why we embed microprocessors in systems.
■ What is difficult and unique about embedding computing.
■ Design methodologies.
■ System specification.
■ A guided tour of this book.
INTRODUCTION
In this chapter we set the stage for our study of embedded computing system design.
In order to understand the design processes, we first need to understand how and
why microprocessors are used for control, user interface, signal processing, and
many other tasks. The microprocessor has become so common that it is easy to
forget how hard some things are to do without it
COMPLEX SYSTEMS AND MICROPROCESSORS
What is an embedded computer system? Loosely defined, it is any device that
includes a programmable computer but is not itself intended to be a general-purpose
computer.Thus,a PC is not itself an embedded computing system,although PCs are
often used to build embedded computing systems. But a fax machine or a clock
built from a microprocessor is an embedded computing system.
Performance in Embedded Computing
When we talk about performance when writing programs for our PC, what do
we really mean? Most programmers have a fairly vague notion of performance—
they want their program to run “fast enough” and they may be worried about
the asympototic complexity of their program. Most general-purpose programmers
use no tools that are designed to help them improve the performance of their
programs.
Embedded system designers, in contrast, have a very clear performance goal in
mind—their program must meet its deadline.At the heart of embedded computing
is real-time computing,which is the science and art of programming to deadlines.
The program receives its input data; the deadline is the time at which a computation
must be finished. If the program does not produce the required output by the
deadline, then the program does not work, even if the output that it eventually
produces is functionally correct
In order to understand the real-time behavior of an embedded computing system,
we have to analyze the system at several different levels of abstraction. As we move
through this book, we will work our way up from the lowest layers that describe
components of the system up through the highest layers that describe the complete
system. Those layers include