Embedded Systems Textbook By Rajkamal Pdf Free Download
An embedded system is a computer that has been built to solve only a few very specific problems and is not easily changed.In contrast, a general-purpose computer can do many different jobs, and can be changed at any time with new programs for new jobs.
An embedded system usually does not look like a computer, often there is no keyboard or monitor or mouse. But like any computer it has a processor and software, input and output. The word embedded means it is built into the system. It is a permanent part in a bigger system.
For example, a controller is embedded in an elevator and tells the motor to move the elevator to different floors based on buttons that are pushed. A decoder is embedded in a satellite television set-top box to read a signal from the dish and send something that a TV understands. Often this type of system must do its work in a specific amount of time. This is called real-time computing. If a set-top box got interrupted to do another task, you would see a bad picture on the TV, for example. A general purpose computer will often have short pauses while it does something else, it is not real-time.
Embedded systems control many of the common devices in use today, from card readers in hotel door locks to many controls in a car. They can be small like an MP3 player or a digital camera, to large systems like traffic lights, airplane controls, or assembly linecontrollers in a factory.
Common features of Embedded Systems
- Embedded systems are designed to do a specific task, unlike general-purpose computers.
- It does not look like a computer - there may not be a full monitor or a keyboard.
- Many embedded systems must be able to do things in real-time - in a short amount of time (almost instantly from a human view).
- Many embedded systems must be very safe and reliable, especially for medical devices or avionics controlling airplanes.
- Starts very quickly. People don't want to wait a minute or two for their car to start or emergency equipment to start.
- It uses a special operating system (or sometimes a very small home-made OS) that helps meet these requirements called a real-time operating system, or RTOS.
- The program instructions written for embedded systems are referred to as firmware, and are stored in read-only memory or flash memory chips. They run with limited computer hardware resources: little memory, small or non-existent keyboard and/or screen.
