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EMBEDDED SYSTEM DESIGN
Definition :
An embedded system is nothing but general purpose computer which is used (or) specified to do a particular task (or) job.
Embedded systems are found in a variety of common electronic devices, such as:
1) Consumer electronics.
2) Home appliances.
3) Office automation.
4) Business equipment.
5) Automobiles.
Characteristics of embedded systems :
1) Single – functioned:- An embedded system usually executes a specific program repeatedly. For example, a pager is always a pager. In contrast, a desktop system executes a variety of programs like spreadsheets, wordprocessors and videogames with new programs added frequently.
1) Tightly constrained:- All computing systems have constraints on design metrics, but those an embedded systems can be especially tight. A design metric is a measure of an implementation’s features such as cost, size, performance and power. Embedded systems often must cost just a few dollars, must be sized to fit on a single chip, must perform fast enough to process data in real time and must consume minimum power to extend battery life.
2) Reactive and real time:- Many embedded systems must continually react to changes in the system’s environment and must compute certain results in real time without delay. For example, a car’s cruise controller continually monitors and reacts to speed and brake sensors. It must compute acceleration (or) declaration amounts repeatedly with in a limited time; a delayed computation could result in a failure to maintain control of the car.
Common design metrics :-
A design metric is a measurable feature of a system’s implementation. Commonly used metrics include:
• NRE cost (Non recurring engineering cost):- The one-time monetary cost of designing the system. Once the system is designed, any number of units can be manufactured
without incurring any additional design cost: hence the term nonrecurring.
• Unit cost:- The monetary cost of manufacturing each copy of the system, excluding NRE cost.
• Size:- The physical space required by the system, often measured in bytes for software, and gates (or) transistors for hardware.
• Performance:- The execution time of the system.
• Unit cost:- The monetary cost of manufacturing each copy of the system, excluding NRE cost.
• Size:- The physical space required by the system, often measured in bytes for software, and gates (or) transistors for hardware.
• Performance:- The execution time of the system.
• Power:- The amount of power consumed by the system, which may determine the lifetime of a battery, or the cooling requirements of the IC, since more power means more heat.
• Flexibility:- The ability to change the functionality of the system without incurring heavy NRE cost; software is typically considered very flexible.
• Time-to-prototype :- The time needed to build a working version of the system, which may be bigger or more expensive than the final system implementation, but it can be used to verify the system’s usefulness and correctness and to refine the system’s functionality.
• Time-to-market:- The time required to develop a system to the point that it can be released and sold to customers.
