Whenever the word microprocessor is mentioned, it conjures up a picture of a PC running an application such as a word processor or a spreadsheet
While this is a common application for microprocessors, it is not the only one and the fact is most people use them indirectly in common objects and consumer electronics without realising it. Without the microprocessor, these products would not be as sophisticated or cheap as they are today.
The embedding of microprocessors into equipment and portable devices started before the appearance of the home computer and consumes the majority of microprocessors that are made today. In this way, embedded microprocessors are more deeply ingrained into everyday life than any other electronic circuit that is made.
A large car may have over 50 microcontrollers controlling functions such as the engine through engine management systems, brakes with electronic anti-lock brakes, transmission with traction control and electronically controlled gearboxes, safety with airbag systems, electric windows, air-conditioning and so on. With a well-equipped car, nearly every aspect has some form of electronic control associated with it and thus a need for a microprocessor within an embedded system.
A washing machine may have a popular microcontroller that contains the different washing programs, provides the power control for the various motors and pumps and even controls the display that tells you how the wash cycles are proceeding. Mobile phones contain more processing power than a desktop processor of a few years ago.
Many gadgets contain microprocessors and there are even in kitchen appliances such as bread machines that use microprocessor-based control systems
The word control is very apt for embedded systems because in virtually every embedded system application, the goal is to control an aspect of a physical system such as temperature, motion, and so on using a variety of inputs.
With the recent advent of the digital age replacing many of the analogue technologies in the consumer world, the dominance of the embedded system is ever greater. Each digital consumer device such as a digital camera, DVD or MP3 player all depend on an embedded system to realise the system. As a result, the skills behind embedded systems design are as diverse as the systems that have been built although they share a common heritage.
There are many definitions for this but the best way to define it is to describe it in terms of what it is not and with examples of how it is used.
An embedded system is a microprocessor-based system that is built to control a function or range of functions and is not designed to be programmed by the end user in the same way that a PC is. Yes, a user can make choices concerning functionality but cannot change the functionality of the system by adding/replacing software.
With a personal computer, this is exactly what a user can do: one minute the PC is a word processor and the next it’s a games machine simply by changing the software. An embedded system is designed to perform one particular task albeit with choices and different options. The last point is important because it differentiates itself from the world of the PC where the end user does reprogram it whenever a different software package is bought and run.
However, PCs have provided an easily accessible source of hardware and software for embedded systems and it should be no surprise that they form the basis of many embedded systems. To reflect this, there are manygreat microcontroller projects to build a simple hobby gadget or a sophisticated data logging system for a race car.
If this need to control the physical world is so great, what is so special about embedded systems that has led to the widespread use of microprocessors?
There are several major reasons and these have increased over the years as the technology has progressed and developed.