Embedded Systems



Embedded systems are everywhere around us, they are made up from combining hardware and software embedded in it as a significant component, embedded systems are either fixed in capability or programmable, that does a specified function. Cars, mobile phones, washing machines,etc.. all are examples of embedded systems.

What Does embedded systems consist of?
There are three important components that made the embedded system up to us which are : hardware, software, and time operating system. Hardwares consist of processors, system application specific circuits, timers, and memory. Softwares must do a specific tasks in a series, so it has a software that keeps in view three constrains which are : availability of system memory, availability of processor speed, and the need to limit the power dissipation. Moving on to the last component, time operating system, it organizes the system and provides a technique that lets the processor run as per scheduling and then switches from one processor to the other.

What are the important characteristics of embedded systems?
-speed: (high speed)
-Power: (low power dissioation)
-size: and weight (smallest and lowest weight and sizes.)
-accuracy: Must be (100%) accurate
-Adaptibilty : (Hight adaptibility and accessibility).
-reliability : Must be reliable over a long period of time.

Embedded systems are classified according to their practical and performance into four categories:
1 - Stand Alone Embedded systems :
It is a system that works by itself, and does not need a host system like a computer. It takes digital or analogs as inputs, and do some proccessing to them and outputs the data as it is attached to the output service.
2 - Real-Time system :
It gives the output in a specific time, so it basically follows deadlines to complete the tasks. The following two systems are the types of Real Time system
A - Hard Real-Time system :
Those systems interact usually with physical hadwares instead of interacting with a humanbeing. Violating time will effect on it so that it will cause damage or calamity.
B - Soft Real-Time system :
It is fine if it misses some deadlines, but it will weaken this system after several deadlines missed, so it might get worse if the number of deadlines missed increased.
3 - Networked Embedded systems :
It is related to network interfaces, so that it can be either in a local area (LAN), or the internet, or a wide area(WAN). It can be connected by wires or wireless.
4 - Mobile Embedded systems :
The basic outline of mobile embedded systems is the memory limitation and other resources. Some examples of mobile embedded systems are most of the portable devices such as mobiles, digital cameras.

My Questions :
1 - What is the mechanic of getting it to work ?
2 - Why Soft Real-Time systems would miss the deadlines eventually?
3 - How does missing deadlines affect on real-time systems?
4 - When do we consider the system as reliable ?
5 - How does time operating system organizes the time?

references :
-photo's link http://www.slideshare.net/murugan_m1/embedded-system-basics