08-16-2017, 09:29 PM
1.1 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.
1.1.1 Embedding Computers
A microprocessor is a single-chip CPU. Very large scale integration (VLSI)
stet the acronym is the name technology has allowed us to put a complete CPU
on a single chip since 1970s, but those CPUs were very simple. The first
microprocessor- the Intel 4004, was designed for an embedded application,
namely, a calculator. The calculator was not a general-purpose computer it
merely provided basic arithmetic functions. However, Ted Hoff of Intel realized
that a general-purpose computer programmed properly could implement the
required function, and that the computer-on-a-chip could then be reprogrammed
for use in other products as well. Since integrated circuit design was (and still
is) an expensive and time- consuming process, the ability to reuse the
hardware design by changing the software was a key breakthrough. The HP-35
was the first handheld calculator to perform transcendental functions [Whi72]. It
was introduced in 1972, so it used several chips to implement the CPU, rather
than a single-chip microprocessor. How- ever, the ability to write programs to
perform math rather than having to design digital circuits to perform
operations like trigonometric functions was critical to the successful design of the
calculator.
