i

ii

iii

PASSWORD CONTROLLER BASEDAPPLIANCE

G. SUMA CHANDANA (05S31A0436)

K. CHETAN (05S31A0404)

Department of Electronics & Communication EngineeringSLC’s Institute of Engineering & Technology

(Affiliated to JNT University, Hyderabad)Piglipur (V), Hayathnagar (M)

Hyderabad-5015122009

iv

MINIPROJECT REPORT

ON

PASSWORD CONTROLLER BASED APPLIANCE

Submitted in partial fulfillment of the requirement for the award of theDegree of

Bachelor of Technology in Electronics & Communication Engineering

By

G. SUMA CHANDANA (05S31A0436)

K. CHETAN (05S31A0404)

Department of Electronics & Communication EngineeringSLC’s Institute of Engineering & Technology

(Affiliated to JNT University, Hyderabad)Piglipur (V), Hayathnagar (M)

Hyderabad-5015122009

v

SLC’s INSTITUTE OF ENGINEERING AND TECHNOLOGY

Survey No 17/2, Piglipur Village, Near Ramoji Film City, Hyderabad. 501 512

(Affiliated to Jawaharlal Nehru Technological University)

Website: www.slciet.com email: enquiry@slciet.com

CERTIFICATE

This is to certify that the project report entitled “PASSWORD

CONTROLLER BASED APPLIANCE” being submitted by Miss. G. SUMA

CHANDANA (05S31A0436), Mr. K. CHETAN (05S31A0404) in partial

fulfillment for the award of the degree of Bachelor of Technology in Electronics and

Communication Engineering to the JAWAHARLAL NEHRU

TECHNOLOGICAL UNIVERSITY is a record of bonafied work carried out by him

under my guidance and supervision.

The results embodied in this project report have not been submitted to any other

University or Institute for the award of any Degree or Diploma.

PROF. K.V.S.S.S.S. SAIRAM Mrs. A. RAJAKUMARI

Head of the ECE Department Associate Professor

SLC’s Institute of Engg & Tech Internal Guide

Department of ECE

SLC’s Institute of Engg & Tech

vi

ACKNOWLEDGEMENT

We would like to express our appreciation to Mrs. A. RAJAKUMARI,

Professor in ECE department, our project guide for her dynamic invaluable

technical guidance and constant encouragement, without which we could not

have completed our project work successfully.

We are also grateful to Prof. K.V.S.S.S.S.SAIRAM , Head of

Department in ELECTRONICS AND COMMUNICATIONS Engineering,

whose guidance have provided us enough strength and confidence in attaining

the goal in a designed manner.

We are also very thankful to our college Principal C.SRI RAM whose

constant interest and support went a long way in the timely completion of this

mini project work.

We feel it as a pleasure to convey our regards to P.SRIDHAR, for his

esteemed guidance and support in completing the work in time.

We are very thankful to our college Secretary T.SATYANARAYANA

whose constant interest and support went a long way in the timely completion of

this mini project work.

We express our thanks to all the faculty members who have co-operated

directly or indirectly in the successful completion of this mini project work.

G. Suma Chandana (05S31A0436)

K. Chetan (05S31A0404)

vii

ABSTRACT

Security is a prime concern in our day-to-day life. Everyone wants to be as much

secure as possible. An access control for any appliances forms a vital link in a security

chain. The microcontroller based light is an access control system that allows only

authorized persons to access restricted devices.

Present project deals with the activation of the power supply of an electric bulb.

The system is fully controlled by the 8 bit microcontroller P89V51RD2 which has a

flash for the program memory. The password is stored in the flash memory.

The system has a Keypad by which the password can be entered through it. The user

entered password is compared with the password in the flash memory. When the entered

password matches with the password stored in the memory then the relay gets activated,

LCD displays as “ACCESS GRANTED” and the bulb glows. If the password entered is

wrong then the LCD displays that “ACCESS DENIED”. The same password is then used to

off the bulb.

The system uses 16*2 alphanumeric LCD that displays the password in a secure way

entered using the keypad of 4*3 push button switches. The total circuit enhances the user to

provide a secured operation. The application can be used with various appliances like door

lock system, alarm systems etc. The security provides an advance feature for the present

home automation industry.

viii

INDEX

CHAPTER 1 : INTRODUCTION

CHAPTER 2 : BLOCK DIAGRAM

CHAPTER 3 : COMPONENTS SPECIFICATION

CHAPTER 4 : SCHEMATIC OF MOTHER BOARD

CHAPTER 5 : FLOW CHART

CHAPTER 6 : SOURCE CODE

CHAPTER 7 : APPLICATIONS & FUTURE ASPECTS

CHAPTER 8 : CONCLUSION

APPENDICES

BIBLOGRAPHY

ix

TABLE OF CONTENTS

CHAPTER TOPIC PAGE

NO

1 INTRODUCTION 5

2 BLOCK DIAGRAM 6

2.1 System Description 7

2.2 System Installation 7

2.3 System Operation 8

3 COMPONENTS SPECIFICATION 9

3.1. Components List 9

3.1.1 P89V51RD2 Micro controller 9

3.1.2 MAX 232 IC 10

3.1.3 ULN 2003 IC 12

3.1.4 16*2 alphanumeric LCD Display 13

3.1.5 4 x 3 Keypad 14

3.1.6 12 V Electromagnetic Relay 16

3.1.7 Regulated Power Supply 17

x

3.1.8 Adaptor 18

3.1.9 Wires 18

3.1.10 Electric Bulb as appliance. 18

4 SCHEMATIC OF MOTHER BOARD 19

4.1 Main Circuit 19

4.2 Power Supply Unit 19

5 FLOW CHART 22

6 SOURCE CODE 24

7 APPLICATIONS & FUTURE ASPECTS 34

8 CONCLUSION 35

APPENDICES 36 - 39

BIBLOGRAPHY 40

xi

LIST OF FIGURES

FIGURE NO TITLE PAGE NO

2.1 Block Diagram of entire system 6

3.1 Pin Configuration of Microcontroller 9

3.2 Pin Configuration of MAX 232 IC 11

3.3 Pin Configuration of ULN 2003 IC 12

3.4 16x2 alphanumeric LCD display 13

3.5 Schematic of 16x2 alphanumeric LCD display 14

3.6 4 x 3 keypad 15

3.7 Matrix keypad connections 15

3.8 Electromagnetic Relay 16

3.9 Relay Schematic Diagram 16

3.10 Block Diagram of Power Supply Unit 17

4.1 Schematic Diagram of Main Circuit 19

4.2 Schematic Diagram of Power Supply Unit 20

LIST OF TABLES

TABLE NUM. TITLE PAGE

NO

3.1 Pin Description of MAX232 11

1

CHAPTER 1

1. INTRODUCTION

There are now a days in the market many different types of Home

Automation Systems that provides many appliances to users which make them

comfortable. The main goal of the project is to develop a very-low cost and small

electronic system that provides security to the home appliances. The appliance

can be light bulb, door lock system or alarming system.

The Password Controller Based Lighting mainly consists of a mother

board circuit that has P89V51RD2 microcontroller, MAX 232 IC and LCD

display. The circuit board also connects components such as 4 x 3 Keypad,

Relay, ULN 2003 IC and a Regulated Power Supply.

The microcontroller has a 64kB of on-chip flash memory and 1024B of

RAM. The microcontroller is programmed such that the LCD displays to enter

the password which is accepted by the keypad. When this password matches with

the password that is entered by the user, the ULN 2003 IC makes the relay to

activate and thus the relay functions to switch the light.

The Regulated Power Supply gives 9V to ULN 2003 IC and 12V to the

relay to function.

2

CHAPTER 2

2. SYSTEM BLOCK DIAGRAM

Figure 2 : Block diagram of the system

NC

NO

GND

Relay

GND

PORT 1.2to 1.7

P2.0-- IN

CC

Port 0.1 to 0.7

Key Pad(4*3)

Bulb

MAX 232

VCC (+5V)

8951RD2 Micro

Controller

ULN 2003

OUT

Power Supply

+12V

LCD DISPLAY

+230V

RPS

Adaptor

GND

3

2.1 System Description:

The system for the password controller has the following components:

1. P89V51RD2 Micro controller

2. MAX 232 IC

3. ULN 2003 IC

4. 16*2 alphanumeric LCD Display

5. 4 x 3 Keypad

6. 12 V Electromagnetic Relay

7. Regulated Power Supply

8. Adaptor

9. Wires and

10. Electric Bulb as appliance.

2.2 System Installation:

The microcontroller, MAX 232 IC, LCD display, resistors, capacitors and diodes

etc., are together soldered in a circuit board. The circuit is connected to the computer

through a serial interface and switched ‘ON’ by an adaptor connected to the mains. The

microcontroller is programmed by software and the serial cable is removed.

The keypad is connected to the microcontroller of port 0.1 to 0.7. Ports 1.2 to 1.7

are used for the LCD display. The port 2.0 pin of microcontroller is connected to 1st pin

of ULN 2003 IC. 8th pin of the ULN 2003 IC is grounded. 9th pin is supplied with 9V

from Regulated Power Supply. The 16th pin of the ULN 2003 IC is connected to the

Relay. The relay has 5 pins in which 1st pin is connected to RPS for 12V power

supply.2nd pin is grounded. One wire of the Power supply and one wire from the bulb are

joined together and the other two wires are connected to remaining two pins. One pin is

left unused.

4

2.3 System Operation:

Password Controller Based Lightening System is used for providing security to the

appliances. The sequence of operations given below shall be followed for operating the

system.

1. Switch ‘ON’ the mains of the bulb, Regulated Power Supply, adapter and switch

in the circuit board.

2. The LCD display prompts to enter the Password. Type in the password from the

keypad provided with push button switches.

3. If the password entered is correct LCD displays as “ACCESS GRANTED” and

the relay activates to glow the bulb.

4. If the password entered is not correct LCD displays as “ACCESS DENIED”.

5. Enter the correct password which makes the bulb glow and off.

We can provide even a door lock in place of bulb. The operation follows same as above.

5

CHAPTER 3

3. COMPONENTS DESCRIPTION

This chapter gives the basic description of the main hardware components required

to make a complete system.

3.1 P89V51RD2 Micro controller:

The P89V51RD2 is 80C51 microcontroller with 64kB flash and 1024 B of data

RAM. The key feature of P89V51RD2 is that it achieves twice the through put at same clock

frequency. The flash memory supports both parallel programming and in serial ISP. Parallel

programming mode offers gang-programming at high speed, reducing programming costs

and time to market. ISP allows a device to be reprogrammed in the end product under

software control. The P89V51RD2 allows the flash program memory to be reconfigured

even while the application is running.

The pin configuration of the microcontroller is described below:

Figure 3.1. Pin configuration of microcontroller

6

1. Ports 0.0 to 0.7, 1.0 to 1.7, 2.0 to 2.7 and 3.0 to 3.7 are 8-bit bidirectional general

purpose I/O ports.

2. is program store enable for external program memory.

3. Pin 9 is for reset, pin 19 and 18 are crystal 1 and 2 used for input and output inverting

amplifier.

4. Pin 20 is ground; pin 30 is used for Address Latch Enable.

5. Pin 31 is External Access Enable; Pin 40 is for Power Supply.

3.2 MAX 232 IC:

Although devices can communicate directly if their Rx and Tx pins are connected

with each other. However to reduce noise interference and increase transmission distance

over wire the voltage levels of logical 0 and 1 are changed. This is usually implemented

using a TTL level conversion chip, called Max-232. this chip accepts the converted high

voltage values and convert them to TTL logical values and present them to

microcontroller, it also accepts the logical value from microcontroller and converts it to

high voltage levels for transmission. The main features of MAX 232 IC are mentioned

below:

Operates From a Single 5-V Power Supply with 1.0 µF Charge-Pump Capacitors

Operates Up To 120 kbit/s

Two Drivers and Two Receivers

±30-V Input Levels

Low Supply Current . . . 8 mA Typical

Applications

− TIA/EIA-232-F, Battery-Powered Systems, Terminals, Modems, and Computers

The Pin diagram:

MAX232 IC has 16pins . The pin diagram of MAX232 IC is shown below:

7

Figure 3.2 : Pin Configuration of MAX 232 IC

Num Name Purpose

1 C1+ + connector for capacitor C1

2 V+ output of voltage pump

3 C1- - connector for capacitor C1

4 C2+ + connector for capacitor C2

5 C2- - connector for capacitor C2

6 V- output of voltage pump / inverter

7 T2out Driver 2 output

8 R2in Receiver 2 input

9 R2out Receiver 2 output

10 T2in Driver 2 input

11 T1in Driver 1 input

12 R1out Receiver 1 output

13 R1in Receiver 1 input

14 T1out Driver 1 output

15 GND Ground

16 VCC Power supply

Table 3.1. Pin Description of MAX232

8

3.3 ULN 2003 IC:

The ULN 2003 IC is a high-voltage, high-current Darlington transistor array. The

main features of the ULN 2003 IC are:

Each consists of seven npn Darlington pairs that feature high-voltage outputs

with common-cathode clamp diodes for switching inductive loads.

The collector-current rating of a single Darlington pair is 500mA.

The Darlington pairs can be paralleled for higher current capability.

High sustaining voltage output 50V MIN.

Output Clamp diodes.

Applications of ULN 2003 include relay drivers, hammer drivers, lamp drivers,

display drivers (LED and gas discharge), line drivers and logic buffers.

The pin configuration of ULN 2003 IC is:

Figure 3.3. Pin Description of MAX232

The IC is of 16-pin monolithic linear IC. It has 7darlington pairs internally, of 7

inputs and 7 outputs i.e.1 to 7 are inputs of Darlington pairs and 10 to 16 are the outputs

.8-pin is ground and 9-pin is common free wheeling diode.

9

3.4 16*2 alphanumeric LCD Display:

Liquid Crystal Displays are created by sandwiching a thin (10-12 micro mm)

layer of a liquid crystal fluid between two glass plates. A transparent, electrically

conductive film or back plane is put up on the rear glass sheet. The transparent sections

of the conductive film in the shape of the desired characters are coated on the front glass

plate. When a voltage is applied between a segment and the back plane, an electric field

is created in the region under the segment. This electric field changes the transmission of

light through the region under the segment film.

Liquid crystal display or LCD is a very commonly used device in electronics

projects to display data and interact with users. LCDs contain s special crystals, which

change their optical characteristics, when electric current is applied to them; this makes

them visible, on a contrast background.

Figure 3.4. 16x2 alphanumeric LCD display

Pin Configuration:

The LCD has 6 lines that can be connected directly to the PIC microcontroller

pins. The 10k potentiometer connected to pin 3 is used to adjust the contrast of the

display.

10

All unused lines should be tied to ground as shown.

Figure 3.5. Schematic of 16x2 alphanumeric LCD display

3.5 4 x 3 keypad:

Keypad is a commonly used device to get user input. Keypads are collection of push

button switches arranged in the form of a matrix. So there are rows and columns of switches.

The two connections of a switch are also connected in the matrix, so that the row has

common connection and column has a common connection. Thus when a button is pressed a

row and a column, where the button is pressed gets connected internally. The output

available from keypad is arranged as rows and columns.

In order to connect the keypad to microcontroller you need to pull the columns pins

high with 10K pull-up resistors. The rows can be connected directly or preferably through

470 ohms current limiting resistors, as when a switch is pressed, the row pin and column pin

will get short.

11

Figure 3.6. 4 x 3 keypad

Scanning and identifying the key:

The fig shows a 4 x 3 matrix connected to two ports. The rows are connected to

an output port and the columns are connected to an input port. If no key has been

pressed, reading the input port will yield 1s for all columns since they are all connected

to high (Vcc). If all the rows are grounded and a key is pressed, one of the columns will

have 0 since the key pressed provides the path to ground. It is the function of the

microcontroller to scan the keyboard continuously to detect and identify the key pressed.

Figure 3.7. Matrix keypad connections

12

3.6 12V Electromechanical Relay:

A relay is a simple electromechanical switch made up of an electromagnet and a

set of contacts. A relay uses an electromagnet. This is a device consisting of a coil of

wire wrapped around an iron core. When electricity is applied to the coil of wire it

becomes magnetic.

Figure 3.8. Matrix keypad connections

To control that devices we are using Electromagnetic switches (Relays) which

are connected to ULN2003 output pins. These Relays can switch 50Hz 250V so we can

directly switch the liner and household devices.

Figure 3.9. Relay Schematic Diagram

13

Advantages of relays:

Relays can switch AC and DC, transistors can only switch DC.

Relays can switch high voltages, transistors cannot.

Relays are a better choice for switching large currents (> 5A).

Relays can switch many contacts at once

3.7 Regulated Power Supply:

Every electronic system requires one or more than one DC voltages for its

operation. It is essential that these DC voltages are nicely filtered and well regulated.

Power supply does the job of providing required DC voltages from available AC mains

in case of mains operated systems and DC input in case of portable systems.

General Block Diagram of a Power Supply Unit: -

The general block diagram of power supply unit is as shown in figure.

Figure 3.10. Block Diagram of Power Supply Unit

Here we use micro controller IC, ULN 2003 IC, MAX 232 IC. All these IC

required supply voltage ranges from 3 to 6 volt d. c. regulated supply and relay required

12V supply. Regulated Power Supply consists of two channels upto a maximum range of

30V. one channel is assigned to relay as its electrical specification is 12v and another

channel with 9 volts is assigned to current Driver chip uln 2003 IC (pin no : 9) for

power supply purpose.

14

Available source for us is 230 V.A.C. mains to convert this A.C. into lower value

A.C. (i.e. step down up to 15 V.A.C.) we use step down transformer of 230 V. primary to

0-15 V (500MA) secondary. After step down we rectify this A.C. to D.C. using full

wave bridge type rectifier. And filter the ripple using filter conductor. For regulated

+5V. d. c. and short circuit overload projection we use voltage regulator IC 7805 and for

12V we use voltage regulator IC 7812.

3.8 Adaptor :

As direct supply from switch board cannot be given to circuit, adapter is used to

step down supply voltage and bring it to desired volt i.e. 12 V essential for circuit to run.

Adapter is close circuit which consist of step down transformer, rectifier etc. The adaptor

connected to power supply of 220v gives output of 5 volts to the circuit board. Its output

specification is 5V/1A DC.

3.9 Wires :

Wires are used for connection purpose. Wires may have single or multi-strength

of metal. They are used as per current capacity. These are insulated wires and have a

low current carrying capacity and soldering metal is used to solder electronic

components on PCB with the help of soldering.

3.10 Appliance Like Bulb :

The output device that is used in this project is an appliance. It can be an electric

bulb, door lock system or any appliance in home automation system.

15

Chapter 4

4. SCHEMATIC DIAGRAM OF MOTHER BOARD

The schematic diagram of the Circuit Board is shown in two parts:

1. Main Circuit.

2. Power Supply Unit

1. Main Circuit:

Figure 4.1. Schematic Diagram of Main Circuit

16

2. Power Supply Unit:

Figure 4.2. Schematic Diagram of Power Supply Unit

17

CHAPTER 5

5. FLOW CHART

DELAY

Clear LCD, Display“ ACCESS DENIED”

Memory Location Clr 40h to 50h

UEPL == APL

Value_UPL == APL value

A

UEPL ==00

Clr Memory Location, Clr UEPL, Clr LCD Location,

Cursor Location

APL = find actual password ()

Clr LCD , Display “Enter Password Length”

Waiting for the user to press the keypad

Start

MSL=3fhUEPL=#00h

(A== *)Back space

A==#

UEPL==15

INC MSLMSL location = A

BC

DE

Y

N

Y

NN

Y

N

Y

Y

N

N

Y

18

Abbreviations in Flow Chart:

MSL : Memory Starting Location = 3Fh

UEPL : User Entered Password Length

APL : Actual Password Length = 9959931760 ( 10 digits)

A

Clr , Display“ ACCESS

GRANTED”

Compliment Port (ON/ OFF)

RELAY

BULB ON/OFF

END

B

Display *

C

DE

19

CHAPTER 5

SOURCE CODE:

The main loops of the source code are give below:

LCD initialization

org 0000h

;MOV P1,#00H

ACALL LCD_INIT

main function

main:MOV R7,#3Fh;Starting location(Storing the Password which is user enter)

mov R5,#00H ; Count for user enter pwd

mov r2,#00H ; user password length ;To Find out lenght of the password

mov DPTR,#PASSWORD

counting loop : This will count no of enterered bits in password and maniplaters the

register operations by taking values from p0.7 to p0.4 output(row) and p0.3 to p0.0

input(col)

still_count: CLR A

MOVC A,@A+DPTR

jz count_completed

inc dptr

Inc R2

sjmp still_count

count_completed:

;Displaying the "Enter Password :"

mov DPTR,#DATA1

ACALL clrscr_display

;Accepting the user password

MOV A,#0C0H

20

ACALL COMMD

ACALL DELAY

mov P0,#0fh ;P0.7 to P0.4 output(row) and P0.3 to P0.0

input(col)

in over loop keypad row scanning will takes place in a sequence from 0 to 3 for

identification for pressed key like:

OVER:

acall delay2

mov a,P0

anl a,#0fh

cjne a,#0fh,over1

sjmp k2

OVER1:

clr P0.4 ; row 1 selected

setb P0.5

setb P0.6

setb P0.7

mov a,P0

anl a,#0fh

cjne a,#0fh,ROW0

ROW0: MOV DPTR,#KCODE0

SJMP FIND

validation loop for “#” character(enter)

valid_to_hash: cjne A,#'#',pwd_enter

sjmp validation

backspace: cjne R5,#00H,bk_continue

LJMP K1

validation loop for “*” character(enter)

max_length_pwd: INC R7

mov r6,01h

21

mov r1,07h

MOV @R1,A

mov r1,06h

mov a,#'*' ; to print * on the LCD

ACALL DATAWRT

inc r5 ;increment LCD display (count)

loop writing data to lcd

DATAWRT: ACALL DELAY

MOV R4,A

ANL A,#0F0H

MOV P1,A

SETB P1.2 ;RS=1

SETB P1.3

NOP

CLR P1.3

MOV A,R4

SWAP A

ANL A,#0F0H

MOV P1,A

SETB P1.2

SETB P1.3

NOP

CLR P1.3

RET

DELAY LOOP

DELAY: MOV R0,#7FH

AGAIN:MOV R1,#0FFH

HERE: DJNZ R1,HERE

DJNZ R0,AGAIN

RET

22

loop for lcd displaying for correct or wrong password and also assigning data bits of

password: DATA1: DB "ENTER PASSWORD : ",0

PASSWORD: DB "9959931760",0

FAIL_MSG: DB "ACCESS DENIED",0

SUCC_MSG: DB "ACCESS GRANTED",0

assigning characters of keypad

KCODE0: DB ' ','#','0','*'

23

CHAPTER 6

6. APPLICATIONS & FUTURE ASPECTS

Password Controller Based Lightening is very useful to provide security to any

appliances. The designed system can be used for control any electrical appliance

,if the respective appliance gets placed in the position of bulb. Like a door lock

system, alarming system etc.

This project can be used in wide variety of areas such as

i. Home Automation i.e for house hold purposes

ii. Industrial Automation like schools, offices etc.

FUTURE ASPECTS:

Some of the pins of the microcontroller are left unused & hence can be used in the

future by defining the functions.

We can control many devices by increasing the ULN2003 IC’s (which are connected

to the microcontroller).

We may implement this project for the industrial purposes also.

This system will act according to the parameters given by the user.

24

CHAPTER 7

7. CONCLUSION:

The objective of this project was to illustrate the design and implementation of a

microcontroller ( P89V51RD2 is 80C51 microcontroller with 64kB flash and 1024 B of data

RAM ) controlled system that could be programmed in keil software. It is monitored by

LCD and controlled with Keypad. The program is dumped in microcontroller by using Flash

Magic software and interfaced with keyboard. It is connected with a sequence of

components such as ULN 2003 IC which is a current driver, relay and appliance like bulb

which is to check functioning.

The testing as well as design and system integration is an important feature of this

project. This is an example of how a practical application can be used to allow a user to

control with an industrial system using the password security and firm software. This project

develops essential skills and knowledge for a process control system, here a Password

controlled one, but this technique could be applied to almost any industrial setting including

robotics and also door lock system by using an appliance like door lock as appliance in place

of bulb .

The project is an example of a practical application which can be performed in an

industrial setting as well as in a control laboratory. This experience develops skills in

designing an security system and process control system with practical applications in an

industrial setting. Through numerous experiments on the manual password entry process,it

was verified that the project is an effective module for an graduate capstone project course.

25

APPENDICES

APPENDIX A

26

27

APPENDIX B

28

29

BIBLOGRAPHY

1. Douglas V.Hall, “Microprocessor And Interfacing”, Tata McGraw-

Hill,2nd edition, 2002.

2. Kenneth J. Ayala, “The 8051 Microcontroller programming

application”, Penram International ,2nd edition, 2003.

3. Muhammad Ali Mazidi and Janice Gillispie Mazidi, “The 8051

Microcontroller and Embedded system”,PEARSON Education, 2nd

edition 2002.

4. Roy Chowdary, “Linear Integrated Circuits”, New Age International

Publications ,2nd Edition,2000.

30

31