1.1 EMBEDDED SYSTEM:
An embedded system is a special-purpose system in which the computer is completely encapsulated by or dedicated to the device or system it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs one or a few predefined tasks, usually with very specific requirements. Since the system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, benefiting from economies of scale. Personal digital assistants (PDAs) or handheld computers are generally considered embedded devices because of the nature of their hardware design, even though they are more expandable in software terms. This line of definition continues to blur as devices expand. With the introduction of the OQO Model 2 with the Windows XP operating system and ports such as a USB port
both features usually Belong to "general purpose computers", — the line of nomenclature blurs even more. Physically, embedded systems ranges from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants. In terms of complexity embedded systems can range from very simple with a single microcontroller chip, to very complex with multiple units, peripherals and networks mounted inside a large chassis or enclosure. 1.2 HISTORY:
In the 1960s, computers possessed an ability to acquire, analyze, process data, and make decisions at very high speeds. However there were some disadvantages with the computer controls. They were: high cost, program complexity, and hesitancy of personnel to learn. However the new concept of electronic devices was evolved. They were called programmable controllers which later became a part of embedded systems. This concept developed from a mix of computer technology, solid state devices, and traditional electro mechanical sequences. The first mass-produced embedded system was the Autonetics D-17 guidance computer for the Minuteman missile released in 1961. It was built from discrete transistor logic and had a hard disk for main memory. REQUIREMENTS OF TYPICAL EMBEDDED SYSTEMS: -
EX: CHEMICAL PLANT: Consider a chemical plant. No. of temperatures have to be measured &based on values certain operations are performed, such as opening a value. INPUT: - From sensors which measure temperatures.
OUTPUT: signal that controls a value.
Ex: MOBILE PHONES: The processor of a mobile phone needs to carry out a great deal of communications protocol processing to make "TELEPHONECAL”.
Fig 1.1 Typical embedded sysytem organisation
* Embedded systems often use a (relatively) slow processor and small memory size with an intentionally simplified architecture to minimize costs. * Programs on embedded systems must often run with limited resources * Embedded system designers use compilers to develop an embedded system. * They often have no operating system or a speciali8zed embedded operating system (often a real-time operating system ). * Programs on an embedded system often must run with resources: often there is no disk drive, operating system, keyboard or screen. may replace rotating media, and a small keypad and screen may be used instead of a PC's keyboard and screen. * Embedding a computer is to interact with the environment, often by monitoring and controlling external machinery. In order to do this, analog inputs and outputs must be transformed to and from digital signal levels.
1.4 APPLICATIONS OF EMBEDDED SYSTEMS:
Some widely used applications of embedded systems are listed below: * Automatic teller machines
* Cellular telephones.
* Computer network.
* Disc drives.
* Thermo stats.
* Security monitoring systems.
* Hand held...