1.1. Microprocessors and Microcontrollers
A digital computer typically consists of three major components: the Central
Processing Unit (CPU), program and data memory, and an Input/Output (I/O) system.
The CPU controls the flow of information among the components of the computer.
also processes the data by performing digital operations.
Most of the processing is
done in the Arithmetic-Logic Unit (ALU) within the CPU.
When the CPU of a computer
is built on a single printed circuit board, the computer is called a minicomputer.
microprocessor is a CPU that is compacted into a single-chip semiconductor device.
Microprocessors are general-purpose devices, suitable for many applications.
computer built around a microprocessor is called a microcomputer.
The choice of I/O
and memory devices of a microcomputer depends on the specific application.
example, most personal computers contain a keyboard and monitor as standard input
and output devices.
A microcontroller is an entire computer manufactured on a single chip.
Microcontrollers are usually dedicated devices embedded within an application.
example, microcontrollers are used as engine controllers in automobiles and as
exposure and focus controllers in cameras.
In order to serve these applications, they
have a high concentration of on-chip facilities such as serial ports, parallel input-
output ports, timers, counters, interrupt control, analog-to-digital converters, random
access memory, read only memory, etc.
The I/O, memory, and on-chip peripherals of
a microcontroller are selected depending on the specifics of the target application.
Since microcontrollers are powerful digital processors, the degree of control and
programmability they provide significantly enhances the effectiveness of the
Embedded control applications also distinguish the microcontroller from its relative,
the general-purpose microprocessor.
Embedded systems often require real-time
operation and multitasking capabilities.
Real-time operation refers to the fact that the
embedded controller must be able to receive and process the signals from its
environment as they are received.
That is, the environment must not wait for the con-
troller to become available.
Similarly, the controller must perform fast enough to
output control signals to its environment when they are needed.
environment must not wait for the controller.
In other words, the embedded controller