Embedded systems-unit-1

ADVANCE
EMBEDDED SYSTEM
DESIGN

What is an embedded system
 An embedded system is an electronic/electro-
mechanical system designed to perform a
specific function and is a combination of both
hardware and firmware (software).

EMBEDDED SYSTEM
To perform a specific function
Combination of both h/w and s/w
May or may not contain an O.S
The firmware of the embedded system is pre-
programmed and it is non alterable by the end user

CLASSIFICATION OF ES
 1. Based on generation
 2. Complexity & performance requirements
 3. Based on deterministic behavior
 4. Based on triggering

1. CLASSIFICATION BASED ON
GENERATION
 First generation : 8 bit µp like 8085- simple h/w –
f/w in assembly code
 Second generation : 16 bit µp and 8/16 bit µc –
instruction set much more complex
 Third generation : 32 bit µp and 16 bit µc – DSP
and ASIC came to picture – pipelining evolved
 Fourth generation : advent of SOC multi core
processors- making use of high performance RTES
 What is next?

2. CLASSIFICATION BASED ON
COMPLEXITY AND PERFORMANCE
 Small scale embedded system:
Simple
Not time critical
Low performance
Low cost
May or may not contain o.s
 medium scale embedded system:
Slight complex in h/w and s/w
Medium performance
Low cost
Usually contain an o.s
 Large scale embedded system :
Highly complex h/w and s/w
Demanding high performance
May contain multi-core processors and co processors
Usually contain RTOS for task scheduling and prioritization management

MAJOR APPLICATION AREAS
 Consumer electronics
 House hold appliances
 Security systems
 Automotive industry
 Telecom
 Computer networking systems
 Healthcare
 Measurement and instrumentation
 Banking & retail
 Card readers

PURPOSE OF EMBEDDED SYSTEMS
Each embedded system is designed to serve the
purpose of any one or a combination of the
following tasks:
 Data collection/storage/representation
 Data communication
 Data processing
 Monitoring
 Control
 Application specific user interface

ELEMENTS OF AN EMBEDDED
SYSTEM
MEMORY
System
core
I/O PORTS
(SENSORS)
O/P PORTS
(ACTUATOR
S)
Other
supporting
IC s and
subsystems
communication
interface

CORE OF THE EMBEDDED
SYSTEM
 The core of the embedded system falls in to any
one of the following categories
1. general purpose and domain specific
processors ( µp, µC, DSP )
2. ASIC(Application specific IC)
3. programmable logic devices (PLD)
4. commercial off-the-shelf components
(COTS)

GPP vs. ASIP
 General purpose processor :
Designed for general computational tasks
E.g.. Processor in the laptop
High volume production
Unit cost for a chip is low
 ASIP instruction set and architecture optimized
to specific application
 ASIP arises when the GPP are unable to meet the
application needs

µP Vs µC
µP
Representing a CPU performing
ALU operations according to a pre
defined set of instructions
It is a dependent unit requires
other chips like timers , memory
chips etc
Doesn't contain built in I/O port
Limited power saving options
Mostly general purpose in design
and operation
µC
Highly integrated chip that contains
CPU, RAM, on chip ROM , timer etc
It is a self contained unit
Most of the processors contain multiple
built in I/O ports
Includes lot of power saving features
Mostly application oriented or domain -
specific

RISC VS CISC
RISC
Lesser no. of instruction
Instruction pipeline
Orthogonal instruction set(operates on
any register and any addressing mode)
Operations are performed on registers
only except load and store
Large no. of registers are available
Programmer needs to write more code
to execute a task
Fixed length instruction
Less silicon usage
With Harvard Architecture
CISC
Greater no. of instructions
Generally no instruction pipelining
Non-orthogonal instruction set
Operations are performed on registers or
memory
Limited no. of registers are available
Programmer can achieve the same with a
single instruction
Variable length instructions
More silicon usage since additional decoder
logic is used for complex instruction
Can be Harvard or Von Neumann

Harvard Vs Von Neumann Architecture
Harvard Architecture
Separate buses for instruction and data
Easier to pipeline
Comparatively high cost
No memory alignment problem
Since data memory and program memory
are stored physically in different locations
no chances for corruption of program
memory
Von- Neumann Architecture
Single shared bus for instruction and data
Low performance compared to Harvard
Cheaper
Allows self modifying codes( modifies while
execution)
Since data memory and program memory
are stored physically in same chip chances
for corruption of program memory

Big endian Vs Little endian
 Specifies the order in which the data is stored in
the memory in multi byte system
 If word length is 2 byte then data can be stored
in 2 ways
 Higher order of data byte at higher memory and
lower order just below that
 Lower order of data byte at higher memory and
higher order just below that

Byte 0
Byte 1
Byte 2
Byte 3
Base address + 0
Base address +1
Base address+2
Base address+3
Little endian – lower order
byte of data at lowest
address
Base address + 0
Base address +1
Base address+2
Base address+3
Byte 3
Byte 2
Byte 1
Byte 0
Big endian
Big endian – higher order
byte of data at lowest
address

Load and store operation
 Load – content of memory location loaded to a register
 Stored- stores the content of data from the specified
register to specified memory
 E.g.. Add contents of memory locations x,y and store the
result in location z
load R1,x
load R2,y
add R3,R1,R2
store R3,z

Instruction pipelining
 conventional instruction execution –fetch-
decode-execute
 Instruction pipelining refers to the overlapped
execution of instructions
 Processing speed can be increased

ASIC
 A micro chip designed to perform a unique
application
 It integrates several functions to a single chip
and there by reduces the cost
 Consumes a very small area and there by helps
in the design of smaller systems
 Can be pre-fabricated or custom fabricated
 Profitable only for large volume productions

Programmable logic devices
 Logic devices can be classified into two (fixed and
programmable)
 Circuits in fixed logic device are permanent- (for one function
or set of functions) –they can not be changed
 PLD offer customers a wide range of logic capacity, features,
speed etc.
 final design is completed much faster than that of fixed logic
device
 During design phase customers can change the circuitry as
often as they want
 PLDs are based on re-writable memory
 Once design is final customers can go into many PLDs as they
need

CPLD AND FPGA
 Two major types of PLDs are field programmable gate
arrays and complex programmable logic devices
 FPGA – highest logic density, most features, highest
performance
 Offers built in h/w processors, clk management systems,
device to device signaling
 Used in wide range of applications telecom, DSP etc
 CPLD - Small amount of logic density
 Offer very predictable timing characteristics and so ideal for
critical control applications
 Usually requires low amount of power
 Very inexpensive
 Ideal for cost-sensitive, battery operated
 Ideal of portable applications such as mobile phones

Advantages of PLD
 Offer customers much more flexibility during
design cycle
 Do not require long lead time for production
part
 Allows customers to orders just number of parts
they need, when they need them
 Can be reprogrammed. To add new feature
simply upload a new programming file to the
PLD via internet

Commercial off-the-shelf components-
COTS
 Provides easy integration and interoperability with existing
system components.
 May be developed around a general purpose/domain
specific processor/application specific processor
 E.g.- remote controlled toy car control units like RF
circuitry part, ADC , UV detectors etc.
 Readily available in the market
 Cheap
 Developer can cut down development time
 since no operational and manufacturing standards end
user should stick to a particular vendor for a particular
COTs
 Manufacturer of the COTS component may withdraw the
product at any time

Memory
 On-chip and off-chip memory
 Program storage memory-nonvolatile
FLASH ROM
EEPROMPROM MROM EPROM
NVRAM

MASKED ROM
 One time programmable
 Pre programmed by the manufacturer
 Make use of hardwired technology for storing
data
 Least expensive
 MROM is permanent in bit storage, it is
not possible to alter the bit information

PROM (OTP)
 Not pre- programmed by the manufacturer
 End user is responsible for programming
 Programmed by PROM programmer which
selectively burns the fuses
 Fuses which are burned represents 0 and not
burned represents 1
 Can not be reprogrammed
 Not useful for development

EPROM
 Gives flexibility to reprogram the same chip
 Stores information by changing the floating gate
of an FET
 Quartz crystal window is used to erase
information
 It needs to be taken out and put in UV eraser
for 20 to 30 min which is time consuming
 Tedious & time consuming

EEPROM
 Information can be altered by using electrical
signals
 Can be reprogrammed in circuit
 Can be erased in few milliseconds
 Capacity is limited compared with standard
ROM

FLASH
 Latest and most popular
 Combines re programmability of EEPROM and
high capacity of standard ROM
 Stores information in array of MOSFET
 Erasing can be done at sector /page level

RAM
•It is data memory
•Read from it & write to it
•RAM is volatile – power turned off,
content destroyed
•Direct access memory

RAM
 SRAM, DRAM AND NVRAM
 SRAM- stores data in the form of voltage
 Made up of flip flop
 Fast .Typical access time is 10ns
 Low capacity
 High cost
 Minimum of 6 transistors are used to build a
memory cell
 Does not require refreshing

DRAM
 Made up of MOSFET and a capacitor
 Requires refreshing
 High capacity
 Less expensive
 Slow . Typical access time is 60ns
 NVRAM
 Its RAM with battery backup
 Contains SRAM and a minute battery
 Life span is around 10 years

Memory shadowing
 Execution of ROM is very slow compared to RAM
 RAM access is three times as fast as ROM
 This is to solve the execution speed problem in
processor based system
 ROM BIOS is read and the system is configured
according to it during system boot up( its time
consuming)
 During boot up copy the BIOS to the shadowed RAM
and write protect the RAM then disable the BIOS
reading

SENSORS AND ACTUATORS
Sensors : that converts energy from one form to
another for any measurement or control
purpose
E.g. Smart running shoe
Actuators:
Which converts signals to corresponding physical
action.
Acts as o/p device

i/o subsystems
 Facilitates the interaction to the embedded system with the
external world
LED:
 o/p device
 Pn junction diode
 Anode to +ve terminal and cathode to –ve terminal
 A resistor in series to limit the current
7 segment LED display
 o/p device to display alphanumeric characters
 8 LEDs
 a- g segments
 Two configurations- common anode and common cathode
 Used for low cost application

Optocoupler
 To isolate two parts or a circuit (for suppressing
interference in data communication, high voltage
separation etc)
 Combines a LED and a photo-transistor in a single
package
 Can be used in i/p and o/p circuits
Stepper motor
 Electro- mechanical device which generates discrete
displacement in response to dc electrical signals
 Dc motor gives continuous rotation
 Consumer electronic products, robotics control,
paper feed mechanism of a printer

 Two phase stepper motor is classified into two.
 Uni polar and bi polar
 Unipolar: contains two winding per phase
 Direction of rotation is controlled by changing
direction of current
 Current in one direction flows through one coil
and in opposite direction through the other coil

 Bipolar:
 Contains single winding per phase for reversing
the motor rotation the current flow through the
winding is reversed.
 The stepping of stepper motor can be
implemented by changing sequence of activation
of the stator windings

Different stepping modes
 Full step: both phases are energized simultaneously
 Wave step: only one phase energized at a time
Step Coil a Coil b Coil c Coil d
1 H H L L
2 L H H L
3 L L H H
4 H L L H
step Coil a Coil b Coil c Coil d
1 H L L L
2 L H L L
3 L L H L
4 L L L H

 HALF STEP: Combination of wave and full
step
 Highest torque and stabilitystep Coil a Coil b Coil c Coil d
1 H L L L
2 H H L L
3 L H L L
4 L H H L
5 L L H L
6 L L H H
7 L L L H
8 H L L H

RELAY
 Electro-mechanical device
 Contains a relay coil made up of insulated wire on a
metal core and a metal armature with one or more
contacts
 When voltage is applied to relay coil , current flows
and generates magnetic field which attracts
armature core and moves the contact point
 Widely used configurations are single pole single
throw normally open, single pole single throw
normally closed, single pole double throw

 Piezo buzzer: is a piezoelectric device for generating
audio indications in embedded application
 Contains piezo electric diaphragm which produces sound
in response to the voltage
 Self driving and external driving (predefined tone and
different tone)
 Push button switch:It is an input device.
 Push to make and push to break (normally closed and
normally opened)
 In the pushed state it breaks/makes circuit connection
 Used for generating a momentary pulse
 Used as reset and start in embedded application
 Depending on the way in which push button interfaced
to the controller it can generate either a HIGH or LOW
pulse

 Key board: input device of user interfacing
 Can use push button switches , but it is a wastage of
port pins
 So matrix key board which reduces the number of
interface connections
 For detecting a key press uses scanning technique.
 To prevent de-bounce issue a technique should be
applied
 s/w technique and h/w technique
 s/w easy to implement and the key is read after de-
bounce delay
 PPI: To extend i/o capabilities of processors
 8255 is popular
 Supports 24 i/o pins which ca be grouped in to 8 bit
parallel ports (port A, port B, port C)

Communication interface
 For communicating with various subsystems of the
embedded system and with external world
On boards communication interfaces
 for interconnecting the various ICs and other peripherals
within embedded system
I2C bus (inter integrated circuit bus)
 Synchronous bidirectional half duplex two wire serial interface
bus
 Comprise of two bus lines, serial clock and serial data (SCL
and SDA)
 Many number of I2C devices can be connected
 Devices connected to I2C can act as master or slave device
 I2C bus three different data rates (100kbps,400kbps,3.4mbps)

Serial peripheral interface SPI bus:
 Synchronous, bidirectional, full duplex four wire serial
interface bus
 It’s a single master multi-slave system
 Requires four signal lines for communication (master out slave
in, master in slave out, serial clock, slave select)
 Master device is responsible for generating the clock signal
 Master selects the required slave device
 SPI works on the principle of shift register. Master and slave
devices contain a special shift register for the data to transmit
or receive.
 Size of SR is device dependent. Normally it is a multiple of 8
 Compared to I2C ,SPI is most suitable for transfer of data in
streams
 Limitation is , it doesn’t support an acknowledgement
mechanism

UART (universal asynchronous Receiver Transmitter)
 Asynchronous form of data transmission
 Serial data transmission doesn’t require a clock signal to
synchronize the end of transmission
 It relies upon the pre defined agreement between the
devices
 For proper communication the transmit line of the
sending device should be connected to the receiving
device
 It also provides h/w handshaking signal support for
controlling the serial data flow
 Nowadays most the microprocessors are available with
integrate UART functionality

1-wire interface
asynchronous half duplex communication protocol
 It makes use of only a single signal line called DQ for
communication and follows master-slave communication
model
 It allows power to be sent along the signal wire as
well.(I2C uses internal capacitor to power the device)
 Supports a single master and one or more slave devices
 Every 1-wire device contains a globally unique 64 bit id
stored within it for addressing
 Communication over the 1-wire bus is divided into
timeslots of 60micro sec

Parallel interface:
 Used for communicating with peripheral device
which are memory mapped to the host of the
system
 Device which supports parallel bus can directly
connect to this bus
 Controlled by the control signal interface between
the device and the host(rd/wr,select)
 Always initiated by host processor, if device wants
to initiate then it should use interrupts
 Direction of data is controlled by rd/wr
 Decoder circuit activates the chip select line to
activate the device

External communication interface
 Channels/buses use by the embedded system to communicate with the
external world
RS 232/ RS 422/RS485:
full duplex, wired, asynchronous serial communication interface
 Developed by EIA( electronics industries association ) during 1960
 Logic 0 is represented with voltage between +3 and + 25,
 logic 1 using voltage between -3 and -25
 Logic 0 is known as space and logic 1 as mark
 Supports baud rates up to 20 kbps
 still popular in industrial applications
 Supports two different types of connectors- DB-9 and DB-25
 Supports only point to point communication
 Not suitable for multi- drop communication
 More susceptible to noise and reduced operating distance

Universal serial bus:Wired high speed serial bus for data communication
 Follows star topology with a USB host at the centre and one or more
USB peripheral devices connected to it.
 Transmits data in packet format
 Improves the noise immunity
 Has the ability to supply power to the connecting devices
 Mini and micro USB connectors are available for small form factor
devices like portable media player
 Supports four different types of data transfers
1 control: s/w to query, configure and issue commands to the USB
device
2 Bulk: for sending block of data to a device,
3 Isochronous data: for real time data communication (data transmitted as
streams in real time. Does not support error checking and
retransmission. Audio devices and medical equipment)
4 Interrupt transfer: for transferring small amount of data.

IEEE 1394( Firewire):
wired, isochronous high speed serial communication bus
 Supports peer to peer connection and point to multipoint
communication
 Allowing 63 devices to be connected on the bus in a tree
topology
 Can support a cable length of up to 15ft
 Supports data rate of 400 to 3200 Mbits/sec
 Supports 3 types of connectors (4pin, 6pin, 9pin)
 Used of devices like digital camera, camcorder for data
transfer and storage
 Unlike USB doesn’t require a host for communicating
between devices (directly connect a scanner with a printer)
 Data rate is far higher than USB
 h/w implementation costlier than USB

Infrared( IrDA):
 serial, half duplex, line of sight based wireless technology for
data( remote control of TV)
 Supports point to point and point to multipoint
communication
 Communication range 10cm to 1m
 IR supports data rates ranging from 9600 bits/s to 16 Mbps
 Infrared light emitting diode is the IR source and photodiode
acts as receiver
 Has two parts , physical link part and a protocol part
 Popular for file exchange and data transfer in low cost devices
 Even now most of the mobile phones supports IrDA

Blue tooth(BT):
 low cost, low power, short range wireless technology for data
and voice
 Supports a data rate of up to 1Mbps
 Range approximately 30ft
 Like IrDA it has two parts
 Each BT device has a 48 bit unique identification number
 Supports point to point and point to multipoint
communication
 A device can act as master or slave
 Popular in mobile phones

Wi-Fi:
 wireless fidelity is popular for wireless
communication for networked communication
 Supports IP protocol
 Each device is addressed by IP address
 An intermediate agent called wi-fi router
 Supports data rate 1Mbps- 150 Mbps
 Offers range of 100- 300ft

ZigBee:
 low power, low cost, wireless n/w protocol
 Supports distance upto 100m
 Supports Data rate of 250Kbps
 3 device category ( coordinator, router, end device)
 Coordinator- acts as the root of the n/w. responsible of
initiating the n/w and can store information about the
n/w
 Router-for passing information from one device to other
 End device-for data communication
 Eg: smoke detector, heating control , lighting control

General packet radio service(GPRS):
 for transferring data over a mobile communication n/w
like GSM
 Data is sent as packets
 At receiving end reconstructed by combining packets
 The radio channel is shared between several users instead
of dedicating to a cell phone user
 Mainly for mobile enabled embedded devices

Embedded firmware
 Refers to the control algorithm and or the configuration
settings that an embedded system developer dumps into the
memory of the embedded system
 Various methods-
 Write program in high level languages like embedded C
 Write the program in assembly language using the instructions
supported by your application’s target processor
 These should be converted to machine code before loading to
the memory which is called ‘ HEX file creation’
 For a beginner it is better to use HLL.(writing code is easy,
highly portable, not developer dependent )
 Assembly language is tedious , time consuming and highly
dependent on developer

Other system components
 Circuits/IC s necessary for the proper functioning
of the embedded system
Reset circuit: to ensure that the device is not
operating at a voltage level when the device is not
guaranteed to operate when power ON
 Reset signal starts the execution from the reset
vector from the address 0x0000
 Either active H or active L
 Some micro processors/controllers contains built in
reset circuitry

Brown-out protection circuit :
 protection circuit prevents the processor/controller
from unexpected program execution behavior when
the supply voltage falls below a specified voltage
 May lead to data corruption
 Essential for battery powered devices
 This holds the processor in reset state until it rises
above the threshold voltage

 Oscillator unit: is responsible for generating
the clock for the processor
 Certain processors integrate built in oscillator
and simply require an external quartz crystal for
producing the clock
 Speed of the processor depends on clock
frequency
 Power consumption increases with increase in
clock frequency
 Accuracy of the program execution depends on
accuracy of clock signal

 Real time clock: for keeping track of time
 Holds information like current time, date, month, year
and day of the week etc.
 Should function even in the absence of power. So
contains a battery back up
 Available in the form of IC s
 Essential for synchronizing the operations of the OS
kernel
 Can interrupt the OS by asserting the interrupt line
 OS kernel identifies the interrupt ( IRQ no)
 The kernel can perform necessary operations like system
date time updation , managing s/w timers etc

Watchdog timer:
To monitor the firmware execution and reset the system
processor when the program execution hangs up.
( alt+ctl+del)
It’s a h/w timer
It inc/dec a counter with each clock pulse and generates a
reset signal when reaches 0
Most processors implement as built in or using an external
IC
When watchdog timeout occurs an interrupt is generated
instead of resetting in modern systems and interrupt
handler handles the situation in an appropriate fashion

PCB and passive components
 Backbone is PCB
 After finalizing the components and the
connection a schematic design is created and
PCB is fabricated
 Apart from subsystems You can have resistor,
capacitor, diodes etc on your board

Characteristics of an embedded
system
 Unlike general purpose computing system, embedded system posses
certain specific characteristics and these are unique.
Application and domain specific: embedded systems are developed to
do the intended functions only
 They can not be used for any purpose
 You can not replace an embedded control unit developed for a
particular domain say telecom with another control unit designed to
sey another domain like consumer electronics
Reactive and real time: emb.sys. are in constant interaction to the real
world
 Any changes happening in the real world (event)are captured by the
sensors or i/p devices
 The event may be periodic or unpredicted one(should not miss)
 So emb.sys. are generally reactive
 Timing behavior or the system should be deterministic
 Should not miss deadlines

Operates in harsh environment: the environment in which the
emb.sys. deployed may be a dusty one or high temperature zone
 System placed in such areas should be capable to with stand all
operating conditions
 Distributed: emb.sys. may be a part of larger system
 Automatic vending m/c contains card reader, vending unit etc.
 They are independent but work together to achieve a common
goal
Small size and weight: size, weight, shape etc will be one of the
deciding factors to choose a product
 Most applications demands small sized and low weight products
Power concerns: designed in such a way as to minimize the heat
dissipation
 May require cooling fan which occupies additional space
 Even it’s a critical constraint battery operated systems, more the
power consumption the less the battery life

Quality attributes of ES
 QA are the non-functional requirements that
need to be documented properly in any system
design.
 If the quality attributes are more concrete and
measurable it will give a positive impact on the
end product
 Operational QA
 Non-operational QA

Operational quality attributes
 Attributes related to e.s when it is in the operational mode or online mode
Response: quickness of the system
 How fast the system is tracking the changes in input variables
 In flight control application any response delay in the system will create
potential damages to the safety of the flight
 Response time for a toy is not time critical
Throughput: efficiency of the system
 Rate of production or operation of a defined process
 Rates can be expressed in terms of units of products , batched produced,
or any other meaningful measurements.
 Generally measured in terms of benchmark (reference point)
Reliability: how much % you can rely upon the proper functioning of sys.
Mean time between failure MTBF (frq of failure in hr/wk/mon) & mean
time to repair MTTR ( how long the system is allowed to be out of order
following a failure ) are the terms used in defining the system reliability

Maintainability: deals with the support and maintenance
to the end user in the case of technical issues and
failures or on the basis of a routine checkup
 As reliability increases maintainability reduced
 Two types (preventive or corrective maintenance)
 User should replace the cartridge after n number of
printouts (scheduled / periodic /preventive)
 If paper feeding part of the printer fails required
immediate repairs (maintenance to unexpected
failure/ corrective)

Security : confidentiality( from unauthorized
disclosure), integrity ( from unauthorized
modification) , availability ( from
unauthorized users)
Safety: deals with the possible damages that
can happen to the operators or public
 Eg. Due to breakdown or emission of
radioactive

Non operational quality attributes
 Attributes that needs to addressed for the product not on the
basis of operational aspects
Testability: & debug ability: how easily one can test her design
and by which mean she can test it.
 h/w testing( peripherals and total h/w function) and firmware
testing
 Debugging the product as such for figuring out the probable
sources that create unexpected behavior in the system
 h/w level debugging ( issues created by h/w problems) and
firmware debugging ( errors that appear as a result of flaws in
the firmware)
Evolvability: related to biology.
 Ease with which the embedded product can be modified to take
advantage of new f/w or h/w technologies

Portability : measure of system independence
 If the product is capable of functioning as such
in various environments
processors/controllers/os
 Product can be ported to a new platform
 Should be flexible and portable
 Assembly language portability is poor

Time to prototype and market
Time to market: time elapsed between the
conceptualization of a product and time at which
the product is ready for selling
 It’s a critical factor because embedded technology is
one where rapid technology change is happening
Time to prototype: its an informal kind of rapid
product development in which the important
features of the product under consideration are
developed
 If prototype is developed faster, the actual
development time can be brought down
significantly.

Per unit cost and revenue : cost will be closely monitored
by both end users
 Proper market study should be carried out before
deciding per unit cost
 During design and development only investment no
returns
 Once the product is ready to sell and its introduced to
the market – product introduction stage
 In growth phase product grabs high market share
 During maturity phase the growth and sales will be
steady and revenue reaches at its peak
 Product retirement/decline phase starts with the drop in
sales volume, market share and revenue
 At some point of decline stage the manufacturer
announces discontinuing of the product
 Unit cost is very high during the introductory stage

Embedded systems-unit-1

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