es module 1 notes pdf

8/9/2019 Es Module 1 Notes PDF

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Module 1

Introduction to Embedded System

An embedded system is one that has computer hardware with software embedded in it as

one of its components.

We can define an embedded system as A microprocessor based system that does not

look like a computer.

We can say that it is A combination of computer hardware and software, and perhaps

additional mechanical or other parts, designed to perform a dedicated function. In some

cases, embedded systems are part of a larger system or product, as is the case of an

antilock braking system in a car.

Embedded system is a special-purpose computer system designed to perform certain

edicated functions. It is usually embedded as part of a complete device including hardware

and mechanical parts. (Wikipedia)

Significance

Due to their compact size, low cost and simple design aspects made embedded systems very

popular and encroached into human lives and have become indispensable. They are found

everywhere from kitchen ware to space craft. To emphasize this idea here are some illustrations.

Embedded systems everywhere

Embedded systems span all aspects of modern life and there are many examples of their use.

a) Biomedical InstrumentationECG Recorder, Blood cell recorder, patient monitor system

b) Communication systemspagers, cellular phones, cable TV terminals, fax and transreceivers,

video games and so on.

c) Peripheral controllers of a computer Keyboard controller, DRAM controller, DMA controller,

Printer controller, LAN controller, disk drive controller.

d) Industrial Instrumentation Process controller, DC motor controller, robotic systems, CNC

machine controller, close loop engine controller, industrial moisture recorder cum controller.

e) Scientificdigital storage system, CRT display controller, spectrum analyser.


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Features of an embedded system

Embedded systems do a very specific task; they cannot be programmed to do different things.

Embedded systems have very limited resources, particularly the memory. Generally, they do

not have secondary storage devices such as the CDROM or the floppy disk.

Embedded systems have to work against some deadlines. A specific job has to be completed

within a specific time. In some embedded systems, called real time systems, the deadlines arestringent. Missing a dead line may cause a catastropheloss of life or damage to property.

embedded systems operate through a

battery, the power consumption has to be very low.

while, pressing ALT-CTRL-DEL is OK

on your desktop,but you cannot afford to reset your embedded system.

environmental conditions such as very

high temperatures and humidity.

the consumer market (for example electronic toys) are very

cost-effective. Even a reduction of Rs.10 is lot of cost saving, because thousands or millions

systems may be sold.

is dominated by Intel and the

operating system is dominated by Microsoft, there is a wide variety of processors and operating

systems for the embedded systems. So, choosing the right platform is the most complex task.

Classification of Embedded Systems

Based on functionality and performance requirements, embedded systems are classified as :

Stand-alone Embedded Systems

Real-time Embedded Systems

Networked Information Appliances

Mobile Devices

Categories of Embedded System

Embedded systems can be broadly divided into following categories This categorization is based

on whether the system has to work as an independent unit or it has to be networked, whether it

has to be performed real-time operations or not etc.


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Simplicity

Machines that perform very simple processes usually have very simple embedded

computers so that the costs of building the computer are much lower. Also, simple

embedded computers can be smaller and use up less energy. Finally, the more simplistic

the computer, the less likely that the computer will fail, according to Embedded Systems.

Time Pressure

Many embedded computers must be able to operate correctly within a certain time frame.

Desktop computers can sometimes perform operations that are not as fast as the

computer user would like, sometimes turning the cursor into an hourglass. However, many

machines that have embedded computers must not have these computers slow down, or

else catastrophe could result, according to Carnegie Mellon.

Durability

Some embedded systems have to be able to withstand harsh environmental conditions.

This is especially the case with automated manufacturing devices. These devices are

often subjected to very high temperatures, cold temperatures, electrical surges and

corrosive materials. They must be designed to resist damage so that they don't fail.

Ease of Use

Embedded computers must operate in a way that is easy for the user to understand. Some

embedded computers, such as the computer found in the microwave, must be designed

so that those with a lack of experience with technology can still use them, according to

Embedded Systems.

Size

Embedded computers usually need to be very small so that they can be stored in small

machines. Many operators do not even realize that the machines they use have

computers embedded in them, according to Carnegie Mellon.

Efficiency

Embedded computers are often designed to conserve power to maximize battery life.

These types of embedded computers shut off electricity flow to certain areas of a machine

that do not need electricity so that no electricity is wasted.


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Reliability

Embedded computers must behave in a consistent and reliable way. Embedded

computers must always perform their expected actions correctly, according to Carnegie

Mellon. Many machines with embedded computers have redundant embedded computers

so that one computer can take over if another one fails.

Easy Repairs

Embedded computers must be designed in a way that makes them easy to repair. Easy

repairs not only save the owners money but also reduce downtime


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Application of embedded systems in automotive

The purpose of an ABS is to temporarily release the brake on a wheel when it rotates too

slowlywhen a wheel stops turning, the car starts skidding and becomes hard to control. It sits

between the hydraulic pump, which provides power to the brakes, and the brakes themselves as

seen in the following diagram. This hookup allows the ABS system to modulate the brakes in

order to keep the wheels from locking. The ABS system uses sensors on each wheel to measure

the speed of the wheel. The wheel speeds are used by the ABS system to determine how to vary


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the hydraulic fluid pressure to prevent the wheels from skidding. The ASC _ T systems job is to

control the engine power and the brake to improve the cars stability during maneuvers. The ASC

_ T controls four different systems: throttle, ignition timing, differential brake, and (on automatic

transmission cars) gear shifting. The ASC _ T can be turned off by the driver, which can be

important when operating with tire snow chains. The ABS and ASC _ T must clearly

communicate because the ASC _ T interacts with the brake system. Since the ABS was

introduced several years earlier than the ASC _ T, it was important to be able to interface ASC _

T to the existing ABS module, as well as to other existing electronic modules. The engine and

control management units include the electronically controlled throttle, digital engine

management, and electronic transmission control. The ASC _ T control unit has two

microprocessors on two printed circuit boards, one of which concentrates on logic-relevant

components and the other on performance-specific components.

Consumer ElectronicsConsumer Electronic items such as toys, air conditions, Refrigerators, Web Enabled TV sets Etc are

embedded systems with varying processing power and memory requirements. Each of these

systems must be highly reliable and low cost.


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Describing a simple Functional blocks of a Digital Camera:

The video signals from transducer(converts real world image into electrical signal) is converted into

digital format using Analog-to-digital converter The signal processing is carried out through the

microprocessor with the associated control circuitry and codecs. Other peripherals such as

CCD(charged couple devices) and interface circuitry are used to transfer digital video to a desktop

computer through host interface. Still and moving - picture digital cameras are very high - end

embedded systems that now includes features such as automatic adjustments of focus, exposure,

flash on/off, etc. Some cameras also embed speech synthesizers, which instruct the user through

voice commands.

Control Systems and Industrial AutomationThis is one of the most widely used application of embedded systems.

Below shows some of the very basic blocks of a generic process control system


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The embedded systems takes electrical signal as input. Generally sensors or transducers convert

physical entity into an electrical signal. These electrical signals are converted to Digital ones, as

processors are designed to handle digital signals. The processor processes these signals using

codes that resides in memory chip. RAMs are used to store volatile data. Most of the times

Embedded Systems are controlling the other systems which depends on the outputs from

Embedded Systems. For such systems Digital to analog converters are used. Not all the blocks are

used for wide verity of Embedded Applications under this handing but can depend on the need of

application. The designers chooses necessary modules and carry out design. While designing,

reliability, performance, and cost need to be kept in mind

Bio-medical Systems

Health care industry is using wide verity of Embedded Systems which are highly time critical and

spontaneous to sensitive responses. Hospitals are full of EEG, ECG units and other diagnosing units

which uses PC add on cards which uses signals from the outputs of the above units and display them

on monitors

Bio-metric embedded systems are widely gaining use in agencies concerned with security. These are

using complex systems, with high memory requirements with pattern recognition algorithms, DSPs for

signal processing, filters, image enhancement techniques, and general purpose processors for

implementing pattern matching algorithms. A simple block diagram of finger print recognition system

is shown below:


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Field Instrumentation

Testing and measuring instruments represents some of the oldest embedded systems.

Instruments that measure parameters such as temperature humidity, voltage, current, power,

frequency, spectrum and other signals performs lots of processing. Response time, display

output, monitoring real time signals with very little time delays are required. So many of them are

time critical when applied to Real time applications.

DSPs are used for measure signal parameters such as video and video signals. The various

protocol analyzers such as ISDN, frame delays have to analyze and simulate complex protocols,

therefore high end processors are used for such embedded systems.

Virtual Instruments are now being used instead of standalone instruments, A PC add on cards

are being used to carry out measurements and the PC resources are used for offline analyzers

and storage of results. A simple block diagram of such an instrument is show below:


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Handheld Computers

Handheld computers with low-cost, 32 bit processors, high computing powers, have been

increasingly used now a days. With a boom in these devices their architecture, forms and usage

spectrum have increased multifold.

A typical block architecture of such device is shown below. These devices runs on a powerful OS

such as Windows CE, Palm OS, Symbian OS, and provides applications

for numerous services(email, calender & address book). These devices also have great

communication powers using USB, IrDA, RS232 serial communication, Ethernet etc.The output

is displayed on LCDS with touch screen. The memory , dynamic RAM and Flash memory has

also have very high capabilities. For audio and video microphones, speakers, digital cameras are

provided.

Data Communication

Internet has worked as catalyst for embedded systems. The modem that connects two computers- is

an embedded system.

Modems:

The dial-up modem normally used to access the Internet are embedded systems with a DSP inside.

Using DSP nd associated software, the modem establishes the connection using standard protocols.

Internet access speeds have increased multifold with advances in embedded systems.

Exp:xDSL(Digital Subscribe Line), HDSL(High Data Rate Digital Subscriber Line), ADSL(Asymmetric

Digital Subscriber Line).

Data Communication Infrastructure: LANCards, Bridges, and routers are all embedded systems.
http://www.jhigh.co.uk/ComputingSG/Images/Animations/digianalog.gifhttp://www.jhigh.co.uk/ComputingSG/Images/Animations/digianalog.gif


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Multimedia Over IP networks: Convergence We use different networks for different services-the telephone(Public Switched Telephone Network or PSTN) for making voice calls and sending

faxes, the Internet for data services such as email, file transfer, & Web services;

and cellular mobile networks for making voice calls while on move. An IP based Wide Area

Network can be back bone network supporting data, voice and video communication services. A

basic architecture is as shown below. IP phones are one of the most powerful Embedded

Systems


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System on chip

SoC not only chip, but more on system. SoC = Chip + Software + Integration

The SoC chip includes: Embedded processor ASIC Logics and analog circuitry

Embedded memory

The SoC Software includes: OS, compiler, simulator, firmware, driver, protocol stackIntegrated

development environment (debugger, linker, ICE)Application interface (C/C++, assembly)

The SoC Integration includes : The whole system solution Manufacture consultant

Technical Supporting

With technological advances that allow us to integrate complete multi-processor systems on a

single die, Systems-on-Chip (SoCs) are at the core of most embedded computing and consumer

devices, such as cell phones, media players and automotive, aerospace or medical electronics.


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A system on a chipor system on chip(SoCor SOC) is anintegrated circuit (IC) that integrates

all components of acomputer or otherelectronic system into a single chip. It may containdigital,

analog, mixed-signal, and often radio-frequency functionsall on a single chip substrate. A

typical application is in the area ofembedded systems.

The contrast with amicrocontroller is one of degree. Microcontrollers typically have under 100 kB

of RAM (often just a few kilobytes) and often really aresingle-chip-systems, whereas the term

SoC is typically used with more powerful processors, capable of running software such as the

desktop versions of Windows andLinux,which need external memory chips (flash, RAM) to be

useful, and which are used with various external peripherals. In short, for larger systems, the

term system on a chip is hyperbole, indicating technical direction more than reality: increasing

chip integration to reduce manufacturing costs and to enable smaller systems. Many interesting

systems are too complex to fit on just one chip built with a process optimized for just one of the

system's tasks.

When it is not feasible to construct a SoC for a particular application, an alternative is asystem in

package (SiP) comprising a number of chips in a single package. In large volumes, SoC is

believed to be more cost-effective than SiP since it increases the yield of the fabrication and

because its packaging is simpler.[1]

Another option, as seen for example in higher end cell phones and on the BeagleBoard, is

package on package stacking during board assembly. The SoC chip includes processors and

numerous digital peripherals, and comes in a ball grid package with lower and upper

connections. The lower balls connect to the board and various peripherals, with the upper balls in

a ring holding the memory buses used to access NAND flash and DDR2 RAM. Memory

packages could come from multiple vendors.

A typical SoC consists of:

A microcontroller, microprocessor or DSP core(s). Some SoCscalled multiprocessor

system on chip(MPSoC)include more than one processor core.

Memory blocks including a selection ofROM,RAM,EEPROM andflash memory.

Timing sources includingoscillators andphase-locked loops.

Peripherals includingcounter-timers, real-timetimers andpower-on reset generators.

Externalinterfaces including industry standards such asUSB,FireWire,Ethernet,USART,

SPI.

Analog interfaces includingADCs andDACs.

Voltage regulators andpower management circuits.
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These blocks are connected by either a proprietary or industry-standardbus such as theAMBA

bus from ARM Holdings. DMA controllers route data directly between external interfaces and

memory, bypassing the processor core and thereby incA SoC consists of both the hardware

described above, and the software controlling themicrocontroller,microprocessor orDSP cores,

peripherals and interfaces. The design flow for a SoC aims to develop this hardware and

software in parallel.

Most SoCs are developed from pre-qualified hardware blocks for the hardware elements

described above, together with the software drivers that control their operation. Of particular

importance are the protocol stacks that drive industry-standard interfaces like USB. The

hardware blocks are put together usingCAD tools; thesoftware modules are integrated using a

software-development environment.

Chips are verified for logical correctness before being sent to foundry. This process is calledfunctional verification and it accounts for a significant portion of the time and energy expended in

the chip design life cycle (although the often quoted figure of 70% is probably an exaggeration).[2]

With the growing complexity of chips, hardware verification languages like SystemVerilog,

SystemC,e,andOpenVera are being used.Bugs found in the verification stage are reported to

the designer.

Traditionally, engineers have employed simulation acceleration, emulation and/or an FPGA

prototype to verify and debug both hardware and software for SoC designs prior to tapeout. With

high capacity and fast compilation time, acceleration and emulation are powerful technologies

that provide wide visibility into systems. Both technologies, however, operate slowly, on the order

of MHz, which may be significantly slower up to 100 slower than the SoCs operating

frequency. Acceleration and emulation boxes are also very large and expensive at $1M+.

FPGA prototypes, in contrast, use FPGAs directly to enable engineers to validate and test at, or

close to, a systems full operating frequency with real-world stimulus. Tools such as Certus

[3]

areused to insert probes in the FPGA RTL that make signals available for observation. This is used

to debug hardware, firmware and software interactions across multiple FPGA with capabilities

similar to a logic analyzer.

After debug the hardware of the SoC follows the place-and-route phase of the design of an

integrated circuit orASIC before it is fabricated reasing the data throughput of the SoC.
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