03-03-2011, 04:51 PM
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CHAPTER 1
INTRODUCTION TO EMBEDDED SYSTEMS
Each day, our lives become more dependent on 'Embedded systems', digital information technology that is embedded in our environment. More than 98% of processors applied today are in embedded systems, and are no longer visible to the customer as 'computers' in the ordinary sense. 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 pre-defined 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. The increasing use of PC hardware is one of the most important developments in high-end embedded systems in recent years. Hardware costs of high-end systems have dropped dramatically as a result of this trend, making feasible some projects which previously would not have been done because of the high cost of non-PC-based embedded hardware. But software choices for the embedded PC platform are not nearly as attractive as the hardware.
Typically, an embedded system is housed on a single microprocessor board with the programs stored in ROM. Virtually all appliances that have a digital interface -- watches, microwaves, VCRs, cars utilize embedded systems. Some embedded systems include an operating system, but many are so specialized that the entire logic can be implemented as a single program.
Definition of Embedded Systems
Embedded system is defined as, for a particular/specific application implementing the software code to interact directly with that particular hardware what we built. Software is used for providing features and flexibility, Hardware = {Processors, ASICs, Memory...} is used for Performance (& sometimes security)
An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, 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.
An embedded system is a single-purpose computer built into a larger system for the purposes of controlling and monitoring the system. A specialized computer system that is part of a larger system or machine.
There are many definitions of embedded system but all of these can be combined into a single concept. An embedded system is a special purpose computer system that is used for particular task.
Overview of an Embedded System Architecture
Every Embedded system consists of a custom-built hardware built around a central processing unit. This hardware also contains memory chips onto which the software is loaded.
The operating system runs above the hardware and the application software runs above the operating system. The same architecture is applicable to any computer including desktop computer. However these are significant differences. It is not compulsory to have an operating system in every embedded system. For small applications such as remote control units, air conditioners, toys etc.
Applications of Embedded Systems
Some of the most common embedded systems used in everyday life are
Small embedded controllers: 8-bit CPUs dominate, simple or no operating system
(e.g., thermostats)
Control systems: Often use DSP chip for control computations
(e.g., automotive engine control)
Distributed embedded control: Mixture of large and small nodes on a real-time
Embedded networks
(e.g., cars, elevators, factory automation)
System on chip: ASIC design tailored to application area
(e.g., consumer electronics, set-top boxes)
Network equipment: Emphasis on data movement/packet flow
(e.g., network switches; telephone switches)
Critical systems: Safety and mission critical computing
(e.g., pacemakers, automatic trains)
Signal processing: Often use DSP chips for vision, audio, or other signal
Processing (e.g., face recognition)
Command and control: Often huge military systems and “systems of systems”
Home Appliances, intercom, telephones, security systems, garage door openers, answering machines, fax machines, home computers, TVs, cable TV tuner, VCR, camcorder, remote controls, video games, cellular phones, musical instruments, sewing machines, lighting control, paging, camera, pinball machines, toys, exercise equipment
Office Telephones, computers, security systems, fax machines, microwave, copier, laser Printer, color printer, paging
Auto Trip computer, engine control, air bag, ABS, instrumentation, security system, transmission control, entertainment, climate control, cellular phone, keyless entry
TYPES OF EMBEDDED SYSTEMS
Based on functionality and performance embedded systems categorized as 4 types
1. Stand alone embedded systems
2. Real time embedded systems
3. Networked information appliances
4. Mobile devices
1. Stand alone embedded systems:-
As the name implies, stand alone systems work in stand alone mode. They take i/p, process them and produce the desire o/p. The i/p can be an electrical signal from transducer or temperature signal or commands from human being. The o/p can be electrical signal to drive another system an led or LCD display
Ex digital camera, microwave oven, CD player, Air conditioner etc
2. Real time embedded systems:-
In this type of an embedded system a specific work has to be complete in a particular period of time.
Hard Real time systems: - Embedded real time used in missiles
Soft Real time systems: - DVD players
3. Networked information appliances:-
Embedded systems that are provided with n/w interfaces and accessed by n/w's such as local area n/w or internet are called Network Information Appliances
Ex A web camera is connected to the internet. Camera can send pictures in real time to any computers connected to the internet
4. Mobile devices:-
Actually it is a combination of both VLSI and Embedded System
Mobile devices such as Mobile phone, Personal digital assistants, smart phones etc are special category of embedded systems
CHAPTER 2
MICROCONTROLLER
Based on the Processor side Embedded Systems is mainly divided into 3 types
1. Micro Processor is for general purpose e.g.: our personal computer
2. Micro Controller is for specific applications, because of cheaper cost we will go for these controllers.
3. DSP (Digital Signal Processor) is for high and sensitive application purpose
MICROCONTROLLER VERSUS MICROPROCESSOR
A system designer using a general-purpose microprocessor such as the Pentium or the 68040 must add RAM, ROM, I/O ports, and timers externally to make them functional. Although the addition of external RAM, ROM, and I/O ports makes these systems bulkier and much more expensive, they have the advantage of versatility such that the designer can decide on the amount of RAM, ROM and I/O ports needed to fit the task at hand.
A Microcontroller has a CPU (a microprocessor) in addition to a fixed amount of RAM, ROM, I/O ports, and a timer all on a single chip. In other words, the processor, the RAM, ROM, I/O ports and the timer are all embedded together on one chip; therefore, the designer cannot add any external memory, I/O ports, or timer to it. The fixed amount of on-chip ROM, RAM, and number of I/O ports in Microcontrollers makes them ideal for many applications in which cost and space are critical.
