Unit – IIntroduction to Embedded System

• Definition – “Embedded systems are computing systems with tightly coupled hardware and software integration, which are designed to perform a dedicated function”.

• Explanation – An embedded system is a combination of computer hardware along with the mechanical or electrical parts, and system software to perform some specific task.

Embedded system and General purpose computer system

• An embedded system refers to “A computer which has been designed to do specialized tasks. Example – Vending machine machine or printer etc.

• General purpose computer system is a combination of hardware and software which performs different task by following the instruction provided by the user .It is not designed to solve any particular problem.

Difference b/w E.S and G.P.Computer systemE.S

• An embedded system is designed to perform some special task.

• It uses simplified circuit.• Less memory is required.• It uses slow processor.• It is low in cost.General Purpose computer system

• It is designed to perform a variety of task.• The circuit is more complex.• It requires more memory.• It requires high speed processor.• It is high in cost

Classification of Embedded System

Classification of E.S

Classification based on the Function

Classification based on Hardware and

software Complexity

Standalone

embedded system

Real Time E.S

Network

Applicatio

n

Mobile Embedded

SystemSmall

Scale E.S

Medium

scale E.S

Sophisticated

E.S

Classification based on the Function

• Standalone E.S – It is built using a specialized communication processor, memory a number of network access interfaces and special software that implements logic for sending information from one device to another decice.

• Real Time E.S – It monitors the

Purpose of E.S

• E.S are small, fast and very powerful tools.• An E.S is a micro-processor based system that is built to

control a function or range of functions .• E.S is designed to perform one or a few dedicated or

specific functions but with choices and different options.• E.S are often required to provide Real-Time response.• A Real-Time is defined as a system whose correctness

depends on the timeliness of its response. Example – flight control system of an aircraft, sensor system in nuclear reactors and power plants.

Why do we need E.S

• General purpose computers like PC’s would be too costly for the majority of products that incorporate some form of E.S technology.

• General purpose computers might fail to meet a number of functional or performance requirements such as constraints in power-consumption, size limitation etc.

• In todays digital world the life totally depends on at least one piece of equipment which contains processor like a phone, television, washing machine etc.

• The power requirement of E.S like cell phone , cameras are very less as compared to the other general purpose computer system.

Application of E.S

Some applications of E.S are as follows:Automobile Sector: E.S is widely used in automobile industries not only in the development of automobiles but also in vehicles for achieving various automated operations.Automobile sector uses the embedded system in the following:Anti-lock braking system(ABS)Electronic Stability Control (ESC/ESP)Traction Control (TCS)Automatic Four-Wheel DriveFuel Injecton ControlAir bags and Automatic brakingCar Entertainment systems

• Telecommunication- This industry utilizes numerous embedded systems from telephone switches for the network to mobile phones at the enduser.

• Telecom industry uses the E.S in the following: In Telephone lines to route data For messaging For other multimedia features in cell phones and

other devices. In network router and bridgesRocket and satellite control.Air Traffic Control.

• Aerospace and Avionics – E.S is more popular in this field because a complex mixture of hardware, electronics and embedded software is required to fulfill the requirements.

• Embedded engineers confront major challenges in this field like:

• Specially designed programs that helps to synchronize the hardware of aero vehicles and the system software of ATC, to take-off and landing the aero-vehicles.

• Ensuring that the complex software and hardware interactions are right.

• Assembling components that meet specifications and perform effectively together.

• Understanding the larger context of the embedded software.

• Consumer Electronics: This field has benefited a lot from embedded technologies like:

• MP3 Players• Mobile Phones• Digital Cameras• PrintersDefense: The defense field also uses the E.S services in RADARs, Guided Missile Systems, automated guns and satellite phones.

Core Components of E.S

Hardware

Processor – or the CPU is responsible for performing all the computational and logical operations in an E.S.Memory – It is odevice which can be used to store data in a system. An E.S can have on-chip or off –chip memory. There are different kinds of memory devices.User Interface – It is a mechanism through which user can provide certain choices to the E.S. These choices are used by the CPU to perform a given task in certain manner. Keypad is one of the most common UI.

Displays – These are used to provide certain information to the user. Alphanumeric Displays and LCD displays are widely used in embedded device.Input/Output: I/O peripherals provide a physical media for Data Transfer with the external world.Other Electrical Components: There are plenty of other active and passive components in an E.S. Examples Power supply, Data Converters etc.

Software

• Control software:- It is responsible for managing different modules of the system.

• Computation Extensive software: - It is responsible for performing mathematical and logical operations on the input data. The output of this can be sent back or stored for later use or can be used by the control software to take certain decisions.

• Device Drivers: - These are the software modules which control system’s peripheral.

• User Interface:- This software is responsible for collecting user inputs and providing “User Menu” or “System Status” to the user.

• Operating system : It is a software which manages the different resources of a system and provides an abstraction of the underlying hardware to the users.

Microprocessors and Microcontrollers

• Microprocessors – It is a programmable integrated circuit that can perform any type of arithmetic or logical operation within a fraction of second.

• It forms a vital role on a computer system.• Microprocessor is a high speed computer with less

storage capacity within it.• It is also called as CPU or Central Processing Unit.• It is the heart of a computer.• It is a complete computation engine that is fabricated

on a single chip.• The first miroprocessor was developed by intel

corporation and named as Intel 4004.

Working of Microprocessor

• A microprocessor executes a collection of machine instructions that tell the processor what task to do.

• A microprocessor does three basic things:-Using ALU it can perform mathematical operations

like addition, subtraction, multiplication and division. It can move data from one memory location to

another. It can make decisions and jump to a new set of

instructions based on those decisions.

Microcontroller

• It is a small computer on a single integrated circuit containing a processor core, memory and programmable input/output peripherals.

• It is designed for personal computers or other general purpose applications.

• They are used in automatically controlled products and devices like automobile engine control systems, applications etc.

• Microcontrollers are special purpose computer.

• Microcontrollers are embedded inside some other device so that they can control the features or actions of the product.It is also called as “embedded controller”.

• They are dedicated to do one task and run one specific program. The programs are stored in ROM.

• They are low power devices ie they consume less power.

• It has a dedicated input device and often has a small LED or LCD display for output.

• It is often small and low cost.

Difference b/w Microprocessor and Microcontroller

Microprocessor – It is a general purpose device that finds its applications in

most of the electronic device. It is a dependant unit that requires other chips for its proper

operation. It is called as a IC which contains many useful functions. It requires external memory devices to stored set of

instructions to carry out user defined tasks. It main use is to read data, perform extensinve calculations on

that data, and store the results in a mass storage device or display the results.

Example for microprocessor is 8085. It uses the memory chips to get the data.

• Microcontroller. It is a specific purpose device which has a specific

task for a sepecfic device. It is an independent device that does not require any

other specific chips. It is called as Microchip which contains the

components of microprocessor. It has the ability to execute a stored set of

instructions to carry out user defined tasks. It is used to control the operations of a machine

using a fixed program that is stored in Rom and does not change over the lifetime of the system.

Example of microcontroller is 8051. It is concerned with getting data from and to its own

pins.

RISC AND CISC Controllers

• RISC – Reduced Instruction Set Computing It is designed to perform a smaller number of types

of computer instructions so that it can operate at a higher speed.

The range of instructions is 30 to 40.It is a type of microprocessor architecture that

utilizes a small, highly-optimezed set of instructions , rather than a more specialized set of instructions often found in other types of architectures.

• CISC- Complex Instruction Set ComputingHere a single instruction can execute several

low-level operations and is capable of performing multi-step operations or addressing modes within single instructions.

Pentium microprocessors are CISC microprocessors.

Difference b/w RISC and CISC

• RISC – It has lesser number of instructions. It uses High level instructions.Provides instruction pipelining. Increased execution speed.Single fixed length instruction.Less silicon and pins are used.Design time is reduced. It uses Harvard Architecture.Large number of registers are available.

• CISC It has more number of instructions.It rarely uses high-level instructions.Instruction pipelining is not used.Comparative lesser speed.Variable length instructions.More silicon and pins are used.Increased design time.Uses Von Neumann Architecture.Limited number of general purpose registers

available.

Big Endian and Little Endian Processors

• Big Endian and Little Endian processors describe the order in which a sequence of bytes are stored in computer memory.

Big Endian is an order in which the most significant value in the sequence is stored first at the lowest storage address.Little Endian is an order in which the least significant value in the sequence is stored first.

Application Specific Integrated Circuits(ASIC)

• It is designed to perform some specific function or task.

• It is a microchip customized for a particular use rather than for general purpose use.

• Ex- A chip designed solely to run a cell phone is an ASIC.

• It include entire 32-bit processors , memory blocks including ROM, RAM, EEPROM, Flash and other large building blocks.

• ASIC is often termed as SoC (System-on-a-Chip).

ASCIsTypes

• ASCIs are categorized according to the technology used for manufacturing them. They are:

• Full-custom- The full custom IC’S are the ASIC that cannot be modified to suit for the different applications.

• These are entirely tailor-fitted to a particular application from the very start.

• As its design and functionality is pre-specified by the user it is manufactured with all the layers fully defined like off-the-shelf general purpose IC’S.

• Semi-custom – These ASCI can be modifies partially.• Semi-custom ASIC’S can be partly customized to serve

different functions within its general area of application.• Semi-custom ASIC’S are designed to allow a certain degree of

modification during the manufacturing process.

• Structured or Platform ASIC –• This belongs to a relatively new ASIC

classification.• These are designed and produced from a

tightly defined set of design methodologies ,intellectual properties and well-characterized silion.

• This type of ASIC is developed for shortening the design cycle and minimizing the development costs of the ASIC.

Programmable Logic Devices(PLD)

• It is an electronic component used to build reconfigurable digital circuits.

• A PLD has an undefined function at the time of manufacture.

• Before the PLD can be used in a circuit it must be programmed that is reconfigured.

Classification of PLD

Classification of Devices

Fixed Logic Devices

FLD

Programmable Logic Devices

PLD

FLD

• The circuits in a FLD are permanent.• They are made to perform one function or set

of functions.• Once FLD’S are manufactured they cannot be

changed.• With FLD’s the time required to go from design,

to prototypes, to a final manufacturing run can take from several months to a year.

PLD

Sensors• Sensors are also called as detectors.• The changes in the system environment or variables are detected

by the sensors connected to the input port of the embedded system.

• It is a transtrucer that converts energy from one type to another type for any particular purpose.

• Example- ECG machine it is designed to monitor the heart beat status of a patient and it canot impose a control over the patient’s heart beat and its order. The sensors are used here are the different electrode sets connected to the body of the patient.

• The variations are captured and presented to the user through a visual display or some printed chart.

Actuators

• Actuator is a form of transducer device which converts signals to corresponding physical action.

• Actuator acts as an output device.• If the embedded system is designed for any controlling

purpose the system will produce some changes in the controlling variable to bring the controlled variable to the desired value. This is achieved through an actuator connected to the output port of the embedded system.

• If the E.S is designed for monitoring purpose only then there is no need for including an actuator in the system.

Types of Actuators

Classification of Actuators

Multi-Turn Actuator Part-Turn Actuator Linear Actuator

Multi-turn Actuator- • It is an actuator which transmits to the valve a

torque for at least one full revolution. It is capable of withstanding thrust.

• It is required for the automation of multi-turn valves.

• One of the main type of this is the gate valve.

Part-turn actuators – • It is an actuator which transmits a torque to the

valve for less than one full revolution. It is not capable of withstanding thrust.

• The major representatives of this type are butterfly valves and ball valves.

Linear Actuator – • The major representative of this type are the

control valves.• Just like the plug in the bathtub is pressed into

the drain the plug is pressed into the plug seat by a stroke.

Communication Interface

• These are the devices through with the E.S can interact with various subsystems and the external world.

• For embedded product communication interface can be viewed in two different perspectives :

1)Device/board level communication interface(On board communication Interface)2)Product level communication interface (External communication interface)

Onboard communication Interface

• The communication channel which interconnects the various components within an embedded product is referred as device/broad level communication interface.

• Examples – Serial interfaces like I2C,I-Wire, and parallel bus interface.

External Communication interface

• These are the E.S which may be a part of large distributed system and they require interaction and data transfer between various devices and sub-modules.

• The product level communication interface is responsible for data transfer between the E.S and other devices or modules.

• The external communication interface can be either a wired media or a wireless media and it can be a serial or a parallel interface.

• Examples – Infrared (IR), Bluetooth(BT), Wireless LAN (Wi-Fi),Radio Frequency waves etc.

On Board Communication Interface

Inter Integrated Circuit Bus (I2C Bus) –• It is a synchronous bi-directional half duplex two –

wire serial bus which provides communication link between integrated circuits.

• It was designed by Philips Semiconductors in 1980s.• It was developed to provide an easy way of

connection between a microprocessor / microcontroller system and peripheral chips in television sets.

• It comprises of two bus lines i.e Serial Clock-SCL and Serial Data-SDA.

• SCL line is responsible for generating synchronisation clock pulses.

• SDA is responsible for transmitting the serial data across devices.• I2C bus is a shared bus system to which many number of I2C

devices can be connected.• Devices connected to the I2C nus can act as either “Master”

device or “Slave” device.• The Master device is responsible for controlling the

communication by initiating or terminating data transfer, sending data and generating necessary synchronisation clock pulses.

• The Slave devices wait for the commands from the Master and respond upon receiving the commands.

• Master and Slave devices can act as either transmitter or receiver.

• Regardless whether a master is acting as transmitter or receiver the synchronisation clock signal is generated by Master device only.

• I2C supports multi masters on the same bus.

External Communication Interfaces• Infrared – Infrared is a serial ,half duplex, line of sight based wireless technology for data communication between devices.The remote control of TV, AC works on the infrared data communication principle.IR uses infrared waves of the electromagnetic spectrum for transmitting the data.It supports point-point and point-to-multipoint communication.The typical communication range for IR lies in the range of 10 cm to 1m.The range can be increased by increasing the tranmitting power of the IR device.IR supports data rates ranging from 9600bits/sec to 16Mbps.

Embedded Firmware

UNIT –IICharacteristics and Quality Attributes of E.S

Embedded systems possess certain specific characteristics and these are unique to each embedded system.1. Application and domain specific 2. Reactive and Real Time3. Operates in harsh environments4. Distributed5. Small Size and weight6. Power concerns

Application and Domain Specific – • Each E.S has certain functions to perform and

they are developed in such a manner to do the intended functions only.

• They cannot be used for any other purpose.• Ex – The embedded control units of the

microwave oven cannot be replaced with AC’S embedded control unit because the embedded control units of microwave oven and AC are specifically designed to perform certain specific tasks.

Reactive and Real Time – • E.S are in constant interaction with the real world through

sensors and user-defined input devices which are connected to the input port of the system.

• Any changes in the real world care captured by the sensors or input devices in real time and the control algorithm running inside the unit reacts in a designed manner to bring the controlled output variables to the desired level.

• E.S produce changes in output in response to the changes in the input, so they are referred as reactive systems.

• Real Time system operation means the timing behaviour of the system should be deterministic ie the system should respond to requests in a known amount of time.

• Example – E.S which are mission critical like flight control systems, Antilock Brake Systems (ABS) etc are Real Time systems.

Operates in Harsh Environment –• The design of E.S should take care of the

operating conditions of the area awhere the system is going to implement.

• Ex – If the system needs to be deployed in a high temperature zone, then all the components used in the system should be of high temperature grade.

• Also proper shock absorption techniques should be provided to systems which are going to be commissioned in places subject to high shock.

Distributed – • It means that embedded systems may be a

part of a larger system. • Many numbers of such distributed embedded

systems form a single large embedded control unit.

• Ex – Automatic vending machine. It contains a card reader , a vending unit etc. Each of them are independent embedded units but they work together to perform the overall vending function.

Small Size and Weight –• Product aesthetics(size,weight,shape,style,etc)

is an important factor in choosing a product.• It is convenient to handle a compact device

than a bulky product.• In embedded domain compactness is a

significant deciding factor.

Power Concerns – • Power management is another important

factor that needs to be considered in designing embedded systems.

• E.S should be designed in such a way as to minimize the heat dissipation by the system.

Quality Attributes of Embedded System

Quality attributes are the non-functional requirements that need to be documented properly in any system design.Quality attributes can be classified as Operational quality attributes and non-operational quality attributes.

Quality Attributes of E.S

Operation Q.A Non-Operational Q.A

Throughput

Reliability

Maintainability

Security

Safety

Response

Per Unit and Total Cost

Time to Prototype and Market

Portability

Evolvability

Testability and Debug-ability

Operational Quality Attributes

• The operational quality attributes represent the relevant quality attributes related to the embedded system when it is in the operational mode or online mode.

Operational Q.A are:Response – It is the measure of quickness of the system.It tells how fast the system is tracking the changes in input variables.Most of the E.S demand fast response which should be almost real time.Ex – Flight control application.

Throughput –• It deals with the efficiency of a system.• It can be defined as the rate of production or

operation of a defined process over a stated period of time.

• Ex – In case of card reader throughput means how many transactions the reader can perform in a minute or in an hour or in a day.

• Throughput is generally measured in terms of “Benchmark”.

• A Benchmark is a reference point by which something can be measured.

Reliability – • It is a measure of how much we can rely upon

the proper functioning of the system.• Mean Time Between Failure (MTBF) and Mean

Time To Repair (MTTR) are the terms used in determining system reliability.

• MTBF gives the frequency of failures in hours/weeks/months.

• MTTR specifies how long the system is allowed to be out of order following a failure.

• For embedded system with critical application need, it should be of the order of minutes.

Maintainability – • It deals with support and maintenance to the

end user or client in case of technical issues and product failure or on the basis of a routine system checkup.

• Reliability and maintainability are complementary to each other.

• A more reliable system means a system with less corrective maintainability requirements and vice versa.

• As the reliability of the system of the system increases the chances of failure and non-functioning also reduces thereby the need for maintainability is also reduced.

Security –• Confidentiality, Integrity and availability are

the three major measures of information security.

• Confidentiality deals with protection of data and application from unauthorized disclosure.

• Integrity deals with the protection of data and application from unauthorized modification.

• Availability deals with protection of data and application from unauthorized users.

Safety – Safety deals with the possible damages that can happen to the operator, pubic and the environment due to the breakdown of an E.S .The breakdown of an embedded system may occur due to a hardware failure or a firmware failure.Safety analysis is a must in product engineering to evaluate the anticipated damages and determine the best course of action to bring down the consequences of the damages to an acceptable level.

Non-Operational Quality Attributes

The quality attributes that needs to be addressed for the product not on the basis of operational aspects are grouped under this category.Testability and Debug-ability – • Testability deals with how easily one can test the design,

application and by which means it can be done.• For an E.S testability is applicable to both the embedded

hardware and firmware.• Embedded hardware testing ensures that the peripherals and

total hardware functions in the desired manner, whereas firmware testing ensures that the firmware is functioning in the expected way.

Evolvability – • It is a term which is closely related to Biology.• It is referred as the non-heritable variation.• For an embedded system evolvability refers to the

ease with which the embedded product can be modified to take advantage of new firmware or hardware technology.

Portability-• It is the measure of system independence.• An embedded product is said to be portable if the

product is capable of functioning in various environments, target processors and embedded operating systems.

Time-to-Prototype and Market – It is the time elapsed between the conceptualisation of a product and the time at which the product is ready for selling.Per Unit Cost and Revenue –• Cost is a factor which is closely monitored by

both end user and product manufacturer.• Any failure to position the cost of a

commercial product at a nominal rate may lead to the failure of the product in the market.