An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions,[1] often with real-time computing
constraints. It is usually embedded as part of a complete device including hardware and mechanical parts. In contrast, a general-purpose computer,
such as a personal computer, can do many different tasks depending on programming. Embedded systems control many of the common devices in use today.
Since the embedded system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product,
or increasing the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.
Physically, embedded systems range 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. Complexity varies from low, with a single
microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure.
In general, "embedded system" is not an exactly defined term, as many systems have some element of programmability. For example,
Handheld computers share some elements with embedded systems — such as the operating systems and microprocessors which power
them — but are not truly embedded systems, because they allow different applications to be loaded and peripherals to be connected.
In the earliest years of computers in the 1930-40s, computers were sometimes dedicated to a single task, but were far too large and expensive for
most kinds of tasks performed by embedded computers of today. Over time however, the concept of programmable controllers evolved from traditional
electromechanical sequencers, via solid state devices, to the use of computer technology.
One of the first recognizably modern embedded systems was the Apollo Guidance Computer, developed by Charles Stark Draper at the MIT
Instrumentation Laboratory. At the project's inception, the Apollo guidance computer was considered the riskiest item in the Apollo
project as it employed the then newly developed monolithic integrated circuits to reduce the size and weight. An early mass-produced
embedded system was the Autonetics D-17 guidance computer for the Minuteman missile, released in 1961. It was built from transistor
logic and had a hard disk for main memory. When the Minuteman II went into production in 1966, the D-17 was replaced with a new
computer that was the first high-volume use of integrated circuits. This program alone reduced prices on quad nand gate ICs from
$1000/each to $3/each, permitting their use in commercial products.
Since these early applications in the 1960s, embedded systems have come down in price and there has been a dramatic rise in
processing power and functionality. The first microprocessor for example, the Intel 4004 was designed for calculators and
other small systems but still required many external memory and support chips. In 1978 National Engineering Manufacturers
Association released a "standard" for programmable microcontrollers, including almost any computer-based controllers, such
as single board computers, numerical, and event-based controllers.
As the cost of microprocessors and microcontrollers fell it became feasible to replace expensive knob-based analog components such as
potentiometers and variable capacitors with up/down buttons or knobs read out by a microprocessor even in some consumer products. By
the mid-1980s, most of the common previously external system components had been integrated into the same chip as the processor and
this modern form of the microcontroller allowed an even more widespread use, which by the end of the decade were the norm rather
than the exception for almost all electronics devices.
The integration of microcontrollers has further increased the applications for which embedded systems are used into areas where
traditionally a computer would not have been considered. A general purpose and comparatively low-cost microcontroller may often
be programmed to fulfill the same role as a large number of separate components. Although an embedded system is usually more
complex than a traditional solution in this context, most of the complexity is contained within the microcontroller itself.
Very few additional components may be needed and most of the design effort is in the software. The intangible nature of software
makes it much easier to prototype and test new revisions compared with the design and construction of a new circuit not using an embedded processor.
References
- Wikipedia.org
- Michael Barr. "Embedded Systems Glossary". Netrino Technical Library. Retrieved on 2007-04-21.
