COMPANY PROFILE

It’s important that the technology we implement is the most secure and as secure as

possible.RAD continually explores and remains knowledgeable in the latest

technologies available in the industry.RAD is a company of qualified & committed

professionals who are working with a vision of developing technical excellence in

young engineers and technocrats. India is a powerhouse of technical workforce and

has acquired a lead in providing technical manpower worldwide. However, to become

competent enough for global technical challenges, our engineers need to develop

experience of real projects and products. At RAD we help people develop sharp

technical skills and professional attitude to stay ahead even in the most challenging

circumstances.

However, to become competent enough for global technical challenges, our engineers

need to develop experience of real projects and products. In RAD,emphasis is given

on spending more time in lab to gain hands-on experience in various interfacing

techniques that can be useful in the construction of an embedded system. We are

offering training programs for Electronics/Electrical/Computers/Mechanical/Bio-

medical fields.

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CHAPTER-1

EMBEDDED SYSTEM

1.1 INTRODUCTION TO EMBEDDED SYSTEM

Now a day’s electronics have developed at very fast rate. It plays a major role in the

life of human being and makes it very easy and comfortable. Electronics circuits are

designed to obtain a particular function. For this purpose a no of electronic component

are suitably connected. Embedded systems have proved changing face of today's

industrial scenario. An embedded system is a system is a special-

purpose computer system designed to perform one or a few dedicated functions often

with real-time computing constraints or embedded system employs a combination of

software & hardware to perform a specific function. It is a part of a larger system

which may not be a “computer” Works in a reactive & time constrained environment.

Any electronic system that uses a CPU chip, but that is not a general-purpose

workstation, desktop or laptop computer is known as embedded system. Such systems

generally use microprocessors; microcontroller or they may use custom-designed

chips or both. They are used in automobiles, planes, trains, space vehicles, machine

tools, cameras, consumer and office appliances, cell phones, PDAs and other

handhelds as well as robots and toys. The uses are endless, and billions of

microprocessors are shipped every year for a myriad of applications.

In embedded systems, the software is permanently set into a read-only memory such

as a ROM or flash memory chip, in contrast to a general-purpose computer that loads

its programs into RAM each time. Sometimes, single board and rack mounted

general-purpose computers are called "embedded computers" if used to control.

We are living in the Embedded World. You are surrounded with many embedded

products and your daily life largely depends on the proper functioning of these

gadgets. Television, Radio, CD player of your living room, Washing Machine or

Microwave Oven in your kitchen, Card readers, Access Controllers, Palm devices of

your work space enable you to do many of your tasks very effectively. Apart from all

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these, many controllers embedded in your car take care of car operations between the

bumpers and most of the times you tend to ignore all these controllers.

In recent days, you are showered with variety of information about these embedded

controllers in many places. All kinds of magazines and journals regularly dish out

details about latest technologies, new devices; fast applications which make you

believe that your basic survival is controlled by these embedded products. Now you

can agree to the fact that

These embedded products have successfully invaded into our world. You must be

wondering about these embedded controllers or systems. What is this Embedded

System?

The computer you use to compose your mails, or create a document or analyze the

database is known as the standard desktop computer. These desktop computers are

manufactured to serve many purposes and applications.

You need to install the relevant software to get the required processing facility. So,

these desktop computers can do many things. In contrast, embedded controllers

carryout a specific work for which they are designed. Most of the time, engineers

design these embedded controllers with a specific goal in mind. So these controllers

cannot be used in any other place.

Theoretically, an embedded controller is a combination of a piece of microprocessor

based hardware and the suitable software to undertake a specific task.

These days designers have many choices in microprocessors/microcontrollers.

Especially, in 8 bit and 32 bit, the available variety really may overwhelm even an

experienced designer. Selecting a right microprocessor may turn out as a most

difficult first step and it is getting complicated as new devices continue to pop-up

very often.

1.2 EMBEDDED APPLICATIONS

1.2.1 AUTOMOBILES:

i) Automatic Parking

ii) Tyre Pressure Monitoring

iii) Keyless Entry3

iv) Collision Avoidance System

v) Driver Information & Navigation System Light

vi) Door & Seat Control

Figure 1.1 Embedded System in a car

1.2.2 BUSINESS APPLICATIONS:

Vending Machine, Scanners , Printers

1.2.3MEDICAL ELECTRONICS:

i) Patient Monitoring

ii) Blood Pressure Monitor

iii) Clinical Treatment : Dialysis

iv) Machine

v) Diagnostic Imaging : MRI , CT Scan

vi) Hospital Networking and Information System

Figure 1.2 Blood Pressure Monitor

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1.2.4 CONSUMER ELECTRONICS:

i) Microwave Oven

ii) Air Conditioning System

iii) Home-security & burglar alarm

iv) Audio / Music system

v) DVD(Digital Versatile Disk),Video Player

vi) Mobile , Modem

vii) Washing Machine

Figure 1.3: Consumer Electronics

1.2.5 INDUSTRIAL AUTOMATION APPLICATION:

i)Process Control: Control of chemical plant , oil refinery etc.

ii)SCADA(Supervisory Control & Data Acquisition) : PC control &monitor

smaller controllers mounted in field .

iii) Plant automation: Computer numeric control machines , robots for

manufacturing

iv) Safety Interlocks: Safety systems to avoid life and material hazard , like plant

shutdown if gas leaks.

Figure 1.4 Fabrication equipment

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1.2.6 DEFENCE APPLICATIONS:

RADARs, SONARs (for suvellience) , Guided Missiles System and many more…

1.2.7 ROBOTICS:

Embedded systems are used for making robots.

Figure 1.5: Robot

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CHAPTER-2

MICROCONTROLLER

2.1 INTRODUCTION

Microcontroller are widely used in Embedded System products. An Embedded

product uses the microprocessor(or microcontroller) to do one task & one task only. A

printer is an example of Embedded system since the processor inside it perform one

task only namely getting the data and printing it. Contrast this with Pentium based PC.

A PC can be used for any no. of applications such as word processor, print server,

bank teller terminal, video game player, network server or internet terminal. Software

for variety of applications can be loaded and run. Of course the reason a PC can

perform multiple task is that it has RAM memory and an operating system that loads

the application software into RAM & lets the CPU run it. In and Embedded system

there is only one application software that is typically burn into ROM. An x86PC

Contain or its connected to various Embedded Products such as keyboard, printer,

modem, Disc controller, Sound card, CD-Rom Driver, Mouse & so on. Each one of

these peripherals as a microcontroller inside it that performs only one task. Although

microcontroller are preferred choice for many Embedded systems, There are times

that a microcontroller is inadequate for the task. For this reason in recent years many

manufactures of general purpose microprocessors such as INTEL, Motorolla, AMD &

Cyrix have targeted their microprocessors for the high end of Embedded market.

While INTEL, AMD, Cyrix push their x86 processors for both the embedded and

desktop pc market, Motorolla is determined to keep the 68000 families alive by

targeting it mainly for high end of embedded system. One of the most critical needs of

the embedded system is to decrease power consumptions and space. This can be

achieved by integrating more functions into the CPU chips. All the embedded

processors based on the x86 and 680x0 have low power consumptions in additions to

some forms of I/O, Com port & ROM all on a single chip. In higher performance

Embedded system the trend is to integrate more & more function on the CPU chip &

let the designer decide which feature he/she wants to use.

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2.2 DEFINITION

Microcontroller, as the name suggests, are small controllers. They are like single

chip computers that are often embedded into other systems to function as

processing/controlling unit. For example, the remote control you are using probably

has microcontrollers inside that do decoding and other controlling functions. They are

also used in automobiles, washing machines, microwave ovens, toys ... etc, where

automation is needed.

2.3 HISTORY

Intel Corporation introduced an 8-bit microcontroller called 8051 in 1981

this controller had 128 bytes of RAM, 4k bytes of on chip ROM, two timers, one

serial port, and four ports all are on single chip. The 8051 is an 8 bit processor,

meaning that the CPU can work on only 8 bit data at a time. Data larger than 8 bits

broken into 8- bit pieces to be processed by CPU. It has for I/O 8 bit wide.

2.4 FEATURES

FEATURE QUANTITY

ROM 4K bytes

RAM 128 bytes

Timer 2

I/O pins 32

Serial port 1

Interrupt sources 6

2.5 CHOOSING CRITERIA

a) Meeting the computing needs of the task efficiently and cost effectively

i) Speed, the amount of ROM and RAM, the number of I/O ports and

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timers, size, packaging, power consumption

i) easy to upgrade

iii) cost per unit

b) Availability of software development tools -assemblers, debuggers, C

compilers, emulator, simulator, technical support

c) Wide availability and reliable sources of the microcontrollers.

2.6 8051 ARCHITECTURE OVERVIEW

The 8051 family is one of the most common microcontroller architectures used

worldwide. 8051 based microcontrollers are offered in hundreds of variants from

many different silicon manufacturers.

The 8051 is based on an 8-bit CISC core with Harvard architecture. It's an 8-bit CPU,

optimized for control applications with extensive Boolean processing (single-bit logic

capabilities), 64K program and data memory address space and various on-chip

peripherals.

The 8051 microcontroller family offers developers a wide variety of high-integration

and cost-effective solutions for virtually every basic embedded control application.

From traffic control equipment to input devices and computer networking products,

8051 u.c deliver high performance together with a choice of configurations and

options matched to the special needs of each application. Whether it's low power

operation, higher frequency performance, expanded on-chip RAM, or an application-

specific requirement, there's a version of the 8051 microcontroller that's right for the

job.

When it's time to upgrade product features and functionality, the 8051 architecture

puts you on the first step of a smooth and cost-effective upgrade path - to the

enhanced performance of the 151 and 251 microcontrollers.

TYPES OF ARCHITECTURE

I. Von Neumann Architecture

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II. Harvard Architecture

TABLE 2.1: VON NEUMANN & HARVARD ARCHITECTURE:

Von Neumann

Harvard

Doesn’t distinguish between data and

instructions. Both are stored in same

memory and has same word size.

Instructions and data have different

memory spaces , with separate address ,

data and control buses for each memory

space .

Concurrent instruction and data fetch.

Size of instruction is independent of data

word size.

II.7 BLOCK DIAGRAM OF MICROCONTROLLER:

Fig-2.1-Block diagram of MICROCONTROLLER

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2.8 DIP 40 PIN CONFIGURATIONS:

Figure 2.2: Pin description

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1.VCC: - PIN (40) - This pin is used to supply voltage to the micro controller.

Generally +5V is provided to microcontroller.

2.GND: - PIN (20) - This pin is used for ground.

3.RST: - (PIN 9) It is a Reset Input. When this pin is given a high for the two

continuous machine cycles while the oscillator is running, the device gets resets.

Logical one on this pin stops microcontroller’s operating and erases the contents of

most registers. By applying logical zero to this pin, the program starts execution from

the beginning. In other words, a positive voltage pulse on this pin resets the

microcontroller.

4. ALE: - (PIN 30): - It is an Address latch enable. With the bit set the ALE is

enabled during the MOVX or MOVC instruction. Prior to each reading from external

memory, the microcontroller will set the lower address byte (A0-A7) on P0 and

immediately after that activates the output ALE. Upon receiving signal from the ALE

pin, the external register (74HCT373 or 74HCT375 circuit is usually embedded )

memorizes the state of P0 and uses it as an address for memory chip. In the second

part of the microcontroller’s machine cycle, a signal on this pin stops being emitted

and P0 is used now for data transmission (Data Bus). In this way, by means of only

one additional (and cheap) integrated circuit, data multiplexing from the port is

performed. This port at the same time used for data and address transmission.

5. PSEN : - (PIN 29): - Program Store Enabled is the read strobe to external program

memory. When the AT89C51 is executing code from external memory, This pin is

activated during each machine cycle, except that two activation are skipped during

each access to external data memory. If external ROM is used for storing program

then it has a logic-0 value every time the microcontroller reads a byte from memory.

6. EA / VPP: - (PIN 31): - External access enabled. EA must be strapped to ground

in order to enable the device to fetch code from external program memory location

starting at 0000H to FFFFH. EA should be strapped to VCC for internal program

execution. This pin also receives the 12 -Volt programming enabled voltage during

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Flash Programming, for parts that require 12-volt VPP. Where VPP is a peak to peak

voltage.

7. By applying logic zero to this pin, P2 and P3 are used for data and address

transmission with no regard to whether there is internal memory or not. That means

that even there is a program written to the microcontroller, it will not be executed, the

program written to external ROM will be used instead. Otherwise, by applying logic

one to the EA pin, the microcontroller will use both memories, first internal and

afterwards external (if it exists), up to end of address spaced to VCC for internal

program execution. This pin also receives the 12 -Volt programming enabled voltage

during Flash Programming, for parts that require 12-volt VPP. Where VPP is a peak

to peak voltage.

8. PORT 0 AS INPUT:

With resistors connected to port 0, in order to make it an input, the port must be

programmed by writing 1 to all the bits. In the following code, port 0 is configured

first as an input port by writing 1's to it, and then data is received from the port and

sent to P1.

                                          

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Fig-2.3-P0 port with pull up resistors

Dual Role of Port 0 :-Port 0 is also designated as AD0-AD7, allowing it to be used

for both address and data. When connecting an 8051/31 to an external memory, port 0

provides both address and data. The 8051 multiplexes address and data through port 0

to save pins. ALE indicates if P0 has address or data. When ALE = 0, it provides data

D0-D7, but when ALE =1 it has address and data with the help of a 74LS373 latch.

9. PORT 1

Port 1 occupies a total of 8 pins (pins 1 through 8). It can be used as input or output.

In contrast to port 0, this port does not need any pull-up resistors since it already has

pull-up resistors internally. Upon reset, Port 1 is configured as an output port. For

example, the following code will continuously send out to port1 the alternating values

55h  & AAh

9.1 PORT 1 AS INPUT

To make port1 an input port, it must be programmed as such by writing 1 to all its

bits. In the following code port1 is configured first as an input port by writing 1’s to

it, then data is received from the port and saved in R7 ,R6 & R5.

10. PORT 2

Port 2 occupies a total of 8 pins (pins 21- 28). It can be used as input or output. Just

like P1, P2 does not need any pull-up resistors since it already has pull-up resistors

internally. Upon reset, Port 2 is configured as an output port. For example, the

following code will send out continuously to port 2 the alternating values 55h and

AAH. That is all the bits of port 2 toggle continuously.

10.1 PORT 2 AS INPUT

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To make port 2 an input, it must programmed as such by writing 1 to all its bits. In

the following code, port 2 is configured first as an input port by writing 1’s to it. Then

data is received from that port and is sent to P1 continuously.

DUAL ROLE OF PORT 2

In systems based on the 8751, 8951, and DS5000, P2 is used as simple I/O.

However, in 8031-based systems, port 2 must be used along with P0 to provide the

16-bit address for the external memory. As shown in pin configuration 8051, port 2 is

also designed as A8-A15, indicating the dual function. Since an 8031 is capable of

accessing 64K bytes of external memory, it needs a path for the 16 bits of the address.

While P0 provides the lower 8 bits via A0-A7, it is the job of P2 to provide bits A8-

A15 of the address. In other words, when 8031 is connected to external memory, P2 is

used for the upper 8 bits of the 16 bit address, and it cannot be used for I/O.

11. PORT 3

Port 3 occupies a total of 8 pins, pins 10 through 17. It can be used as input or

output. P3 does not need any pull-up resistors, the same as P1 and P2 did not.

Although port 3 is configured as an output port upon reset. Port 3 has the additional

function of providing some extremely important signals such as interrupts. This

information applies both 8051 and 8031 chips. There functions are as follows:-

Table 2.2: PORT 3 functions

Port Pins Alternate Functions

P3.0 RXD ( serial input port)- This is used in serial communication at

receiver’s side

P3.1 TXD (serial output port)- This is used in serial communication at

transmitter’s side

P3.2 INT0 (external interrupt 0) - This pin is used for providing the

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interrupts.

P3.3 INT1 (external interrupt 1) - This pin is used for providing the

interrupts.

P3.4 T0 (timer 0 external input) - This pin is used for providing the timers.

P3.5 T1 (timer 1 external input) - This pin is used for providing the timers.

P3.6 WR (external data memory write strobe) - This pin is used when we

have to perform a write operation.

P3.7 RD (external data memory read strobe) - This pin is used when we

have to perform a write operation.

P3.0 and P3.1 are used for the RxD and TxD serial communications signals. Bits P3.2

and P3.3 are set aside for external interrupts. Bits P3.4 and P3.5 are used for timers 0

and 1. Finally P3.6 and P3.7 are used to provide the WR and RD signals of external

memories connected in 8031 based systems.

12. ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input (PROG)

during Flash programming. In normal operation, ALE is emitted at a constant rate of

1/ 6 the oscillator frequency and may be used for external timing or clocking

purposes. Note, however, that one ALE pulse is skipped during each access to

external data memory. If desired, ALE operation can be disabled by setting bit 0 of

SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC

instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has

no effect if the microcontroller is in external execution mode.

13.PSE

Program Store Enable is the read strobe to external program memory. When the

AT89S8252 is executing code from external program memory, PSEN is activated

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twice each machine cycle, except that two PSEN activations are skipped during each

access to external data memory.

14. External Access Enable

EA must be strapped to GND in order to enable the device to fetch code from external

program memory locations starting at 0000H up to FFFFH. Note, however, that if

lock bit 1 is programmed, EA will be internally latched on reset. EA should be

strapped to VCC for internal program executions. This pin also receives the 12-volt

programming enable voltage (VPP) during Flash programming when 12-volt

programming is selected.

15. XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

16. XTAL2

Output from the inverting oscillator amplifier.

17. OSCILLATOR CRYSTAL

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier

which can be configured for use as an on-chip oscillator; Either a quartz crystal or

ceramic resonator may be used. To drive the device from an external clock source,

XTAL2 should be left unconnected while XTAL1 is driven. There are no

requirements on the duty cycle of the external clock signal, since the input to the

internal clocking circuitry is through a divide-by-two flip-flop, but minimum and

maximum voltage high and low time specifications must be observed.

2.9 SPECIAL PURPOSE REGISTERS:

SFRs are a kind of control table used for running and monitoring microcontroller’s

operating. Each of these registers, even each bit they include, has its name, address in

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the scope of RAM and clearly defined purpose ( for example: timer control, interrupt,

serial connection etc.). Even though there are 128 free memory locations intended for

their storage, the basic core, shared by all types of 8051 controllers, has only 21 such

registers. Rest of locations are intentionally left free in order to enable the producers

to further improved models keeping at the same time compatibility with the previous

versions. It also enables the use of programs written a long time ago for the

microcontrollers which are out of production now.

2.9.1 CPU Registers:

a) ACCUMULATOR: - It is an 8 – bit register and used as working register for the

Arithmetic, Logical instructions. All the calculations are performed using this register.

It can also be used as General purpose register. It is very necessary for some

instructions. It is denoted by A. A number (an operand) should be added to the

accumulator prior to execute an instruction upon it. Once an arithmetical operation is

performed by the ALU, the result is placed into the accumulator. If a data should be

transferred from one register to another, it must go through accumulator. For such

universal purpose, this is the most commonly used register that none microcontroller

can be imagined without (more than a half 8051 microcontroller's instructions used

use the accumulator in some way).

b) B – REGISTER: - It also an 8 – bit register and can be used as General Purpose

register. It is very necessary for the multiplication and division operations which can

be performed only upon numbers stored in the A and B registers ,without it the

operations are not accomplished. All other instructions in the program can use this

register as a spare accumulator (A).

2.10 PSW-PROGRAM STATUS WORD (BIT ADDRESSABLE)

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Fig-2.4-PROGRAM STATUS WORD

This is one of the most important SFRs. The Program Status Word (PSW) contains

several status bits that reflect the current state of the CPU. This register contains:

Carry bit, Auxiliary Carry, two register bank select bits, Overflow flag, parity bit, and

user-definable status flag. The ALU automatically changes some of register’s bits,

which is usually used in regulation of the program performing.

P - Parity bit:

If a number in accumulator is even then this bit will be automatically set (1),

otherwise it will be cleared (0). It is mainly used during data transmission and

receiving via serial communication.

Bit 1:

This bit is intended for the future versions of the microcontrollers, so it is not

supposed to be here.

OV Overflow:

Sets when the result of arithmetical operation is greater than 255 (deci mal), so that it

cannot be stored in one register. In that case, this bit will be set (1). If there is no

overflow, this bit will be cleared (0).

RS0, RS1 - Register bank select bits:

These two bits are used to select one of the four register banks in RAM. By writing

zeroes and ones to these bits, a group of registers R0-R7 is stored in one of four banks

in RAM.

TABLE-2.3 DIFFERENT COMBINATIONS OF RS0 AND RS1:

RS1 RS2 SPACE IN RAM

0 0 Bank 0 (00h-07h)

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0 1 Bank 1 (08h-0Fh)

1 0 Bank 2 (10h-17h)

1 1 Bank 3 (18h-1Fh)

F0 - Flag 0:

This is a general-purpose bit available to the user.

AC - Auxiliary Carry Flag:

It is used for BCD operations only.

CY - Carry Flag:

It is the (ninth) auxiliary bit used for all arithmetical operations and shift instructions.

The above table shows that RS0 and RS1 are responsible for selecting the particular

Register bank i.e. by using the different combinations of RS0 and RS1 the Register

Banks are selected.

CHAPTER-3

MICROPROCESSOR

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3.1 INTRODUCTION

A microprocessor is a general-purpose digital computer central processing unit

(CPU). Although popularly known as a “computer on a chip” is in no sense a

complete digital computer . The block diagram of a microprocessor CPU is shown,

which contains an arithmetic and logical unit (ALU), a program counter (PC),

a stack pointer (SP),some working registers, a clock timing circuit, and interrupt

circuits.

Fig-3.1-BLOCK DIAGRAM OF A MICROPROCESSOR

3.2 COMPARISON BETWEEN MICROPROCESSORS &

MICROCONTROLLERS

The microprocessor must have many additional parts to be operational as a

computer whereas microcontroller requires no additional external digital parts.

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1.The prime use of microprocessor is to read data, perform extensive calculations on

that data and store them in the mass storage device or display it. The prime functions

of microcontroller is to read data, perform limited calculations on it, control its

environment based on these data. Thus the microprocessor is said to be general-

purpose digital computers whereas the microcontroller are intend to be special

purpose digital controller.

2.Microprocessor is concerned with the rapid movement of the code and data from

the external addresses to the chip, microcontroller is concerned with the rapid

movement of the bits within the chip.

Lastly, the microprocessor design accomplishes the goal of flexibility in the

hardware configuration by enabling large amounts of memory and I/O that could be

connected to the address and data pins on the IC package. The microcontroller

design uses much more limited set of single and double byte instructions to move

code and data from internal memory to ALU.

CHAPTER-4

PERIPHERAL INTERFACING WITH 8051

4.1 LED INTERFACING

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LED can be interface with micro-controller as shown in the fig. 2.7. Here the common

anode configuration is used, in which common end is connected to power supply of

+5V. When the port, to which LED’s are interfaced, have logic “0” on it, LED’s will

glow.

The color of emitted light depends on the composition and condition of the

semiconductor material used, and can be infrared, visible or nearly ultra-violet. An

LED can be used as a regular home light source.

Resistor is used to control flow of current through LED’s and EA pin is always

connected to +Vcc in case of 8051 microcontroller.

USE

A LED can be used as an indicator in ac circuit. The LEDs in a seven segment

display may be connected in common anode or in common-cathode configuration.

Figure 4.1: LED interfacing with 8051 microcontroller

4.2 SEVEN SEGMENT INTERFACING:

The Light Emitting Diode (LED), finds its place in many applications in this modern

electronic fields. One of them is the Seven Segment Display. Seven-segment displays

contains the arrangement of the LEDs in “Eight” (8) passion, and a Dot (.) with a

common electrode, lead (Anode or Cathode). The purpose of arranging it in that

23

passion is that we can make any number out of that by switching ON and OFF the

particular LED’s. Here is the block diagram of the Seven Segment LED arrangement.

Pin configuration of a seven segment display:

Fig-4.2-Seven-Segment Display

Seven Segments are basically of two types:

1. Common Cathode(CC)

All the 8 anode legs uses only one cathode,  which is common.

2. Common Anode (CA)

The common leg for all the cathode is of Anode type.

24

Figure 4.3: Circuit diagram for Common Cathode 7-Segment Display

LCD INTERFACING :

16x2 LCD Description

Fig 4.4-LCD diagram with pins description

LCD pin description:The LCD discuss in this section has the most common

connector used for the Hitatchi 44780 based LCD is 14 pins in a row and modes of

operation and how to program and interface with microcontroller is describes in this

section.

The voltage VCC and VSS provided by +5V and ground respectively while VEE is

used for controlling LCD contrast. Variable voltage between Ground and Vcc is used

to specify the contrast (or "darkness") of the characters on the LCD screen.

RS (register select)

There are two important registers inside the LCD. The RS pin is used for their

selection as follows. If RS=0, the instruction command code register is selected, then

allowing to user to send a command such as clear display, cursor at home etc.. If

RS=1, the data register is selected, allowing the user to send data to be displayed on

the LCD.

25

R/W (read/write)

The R/W (read/write) input allowing the user to write information from it. R/W=1,

when it read and R/W=0, when it writing.

Fig 4.4-LCD Pin Description Diagram

EN (enable)

The enable pin is used by the LCD to latch information presented to its data pins.

When

data is supplied to data pins, a high power, a high-to-low pulse must be applied to this

pin in order to for the LCD to latch in the data presented at the data pins.

D0-D7 (data lines)

The 8-bit data pins, D0-D7, are used to send information to the LCD or read the

contents of the LCD’s internal registers. To displays the letters and numbers, we send

ASCII codes for the letters A-Z, a-z, and numbers 0-9 to these pins while making RS

26

=1. There are also command codes that can be sent to clear the display or force the

cursor to the home position or blink the cursor.

We also use RS =0 to check the busy flag bit to see if the LCD is ready to receive the

information. The busy flag is D7 and can be read when R/W =1 and RS =0, as

follows: if R/W =1 and RS =0, when D7 =1(busy flag =1), the LCD is busy taking

care of internal operations and will not accept any information. When D7 =0, the LCD

is ready to receive new information.

Interfacing of micro controller with LCD display

In most applications, the "R/W" line is grounded. This simplifies the application

because when data is read back, the microcontroller I/O pins have to be alternated

between input and output modes. In this case, "R/W" to ground and just wait the

maximum amount of time for each instruction (4.1 msecs for clearing the display or

moving the cursor/display to the "home position", 160 usecs for all other commands)

and also the application software is simpler, it also frees up a

Fig 4.5-Interfacing of Microcontroller with LCD

microcontroller pin for other uses. Different LCD execute instructions at different

rates and to avoid problems later on (such as if the LCD is changed to a slower unit).

Before sending commands or data to the LCD module, the Module must be

27

initialized. Once the initialization is complete, the LCD can be written to with data or

instructions as required. Each character to display is written like the control bytes,

except that the "RS" line is set. During initialization, by setting the "S/C" bit during

the "Move Cursor/Shift Display" command, after each character is sent to the LCD,

the cursor built into the LCD will increment to the next position (either right or left).

Normally, the "S/C" bit is set (equal to "1").

4.5 STEPPER MOTOR INTERFACING

Stepper motors can be used in various areas of your microcontroller projects such as

making robots, robotic arm, automatic door lock system etc. The construction of

stepper motors (unipolar and bipolar stepper motors ), basic pricipal, different

controlling types (Half step and Full step), Interfacing Techniques

(using L293D or ULN2003).

There are actually many ways you can interface a stepper motor to your controller,

out of them the most used interfaces are:

1. Interface using L293D - H-Bridge Motor Driver

2. Interface using ULN2003/2004 - Darlington Arrays

We will dicuss both connection techniques one by one. The above mentioned methods

need 4 controller pins for interface.

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Figure 4.6: Stepper motor interfacing with microcontroller

Here in this circuit too the four pins "Controller pin 1",2,3 and 4 will control the

motion and direction of the stepper motor according to the step sequence sent by the

controller.

Why to use ULN2003?

It is a driver IC. ULN IC are basically current amplifiers that are used to

interface motor or LED's to controller. Motor needs more current to drive the rotor.

The current at port pins are very less around 25Ma which is amplified to 500ma for

motor operation. So we use current amplifier to drive the motor.

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CHAPTER-5

PROJECT COVERED

30

PASSWORD BASED DOOR LOCKING

SYSTEM

5.1 INTRODUCTION

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

secure as possible. An access control for doors forms a vital link in a security chain. 

The microcontroller based Door locker is an access control system that allows only

authorized persons to access a restricted area. The system is fully controlled by the 8

bit microcontroller AT89C2051 which has a 2Kbytes of ROM for the program

memory. The password is stored in the EPROM so that we can change it at any time.

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

31

entered password equals with the password stored in the memory then the relay gets

on and so that the door is opened .If we entered a wrong password then the alarm will

be switched on.

5.2 Design Strategy

This console project is intended to be a low-end and low-cost system that will focus

mainly on affordability and simplicity rather than connectivity or even ease-of-use.

Hence this will be a stand-alone system that will not need a special communications

interface. These limit the design phase to four sub-systems: keypad, controller, and

visual/mechanical interface.

5.3 Main Modules of the System

LCD (Liquid Crystal Display)

The most commonly used Character based LCDs are based on Hitachi's

HD44780 controller or other which are compatible with HD44580.

Stepper Motor

Stepper motors can be used in various areas of your microcontroller projects such as

making robots, robotic arm, automatic door lock system etc. The construction of

stepper motors (unipolar and bipolar stepper motors ), basic pricipal, different

controlling types (Half step and Full step), Interfacing Techniques (using L293D or

ULN2003).

Power Supply:

The +5 volt supply is useful for both analog and digital circuits. DTL, TTL, and

CMOS ICs will all operate nicely from a +5 volt supply. In addition, the +5 volt

supply is useful for circuits that use both analog and digital signals in various ways.

32

Figure 5.1: Power supply

ULN2003

It is a driver IC. ULN IC are basically current amplifiers that are used to interface

motor or LED's to controller. Motor needs more current to drive the rotor. The current

at port pins are very less around 25Ma which is amplified to 500ma for motor

operation. So we use current amplifier to drive the motor.

Fig-5.2-pin diagram of ULN2003

PROGRAM:

$include(mod51)

org 0000h

main: mov r1, #0ffh

mov r2, #0ffh

mov r3, #0ffh

mov p0, #0ffh

main1: lcall lcdon

lcall lcdenterpass

mov a, #0c4h

lcall cmdw

33

lcall delay

lcall checkpw

lcall delay

lcall delay

ljmp main

lcdon: mov a, #38h

lcall cmdw

lcall delay

mov a, #0Eh

lcall cmdW

lcall delay

mov a, #01h

lcall cmdw

lcall delay

mov a, #06h

lcall cmdw

lcall delay

mov a, #80h

lcall cmdw

lcall delay

ret

lcdenterpass: mov a, #'E'

lcall datw

lcall delay

mov a, #'n'

lcall datw

lcall delay

mov a, #'t'

lcall datw

lcall delay

mov a, #'e'

lcall datw

lcall delay

mov a, #'r'

lcall datw

lcall delay

34

mov a, #' '

lcall datw

lcall delay

mov a, #'P'

lcall datw

lcall delay

mov a, #'a'

lcall datw

lcall delay

mov a, #'s'

lcall datw

lcall delay

mov a, #'s'

lcall datw

lcall delay

mov a, #'w'

lcall datw

lcall delay

mov a, #'o'

lcall datw

lcall delay

mov a, #'r'

lcall datw

lcall delay

mov a, #'d'

lcall datw

lcall delay

ret

checkpw: jb p2.7, savedata1

mov r0, #00h

ljmp savedata

savedata1: jb p2.6, savedata3

mov r0, #01h

ljmp savedata

savedata3: jb p1.7, savedata4

mov r0, #02h

35

ljmp savedata

savedata4: jb p1.0, savedata5

mov r0, #03h

ljmp savedata

savedata5: jb p1.6, savedata6

mov r0, #04h

ljmp savedata

savedata6: jb p1.5, savedata7

mov r0, #05h

ljmp savedata

savedata7: jb p1.4, savedata8

mov r0, #06h

ljmp savedata

savedata8: jb p1.3, savedata9

mov r0, #07h

ljmp savedata

savedata9: jb p1.2, savedata10

mov r0, #08h

ljmp savedata

savedata10: jb p1.1, checkpw

mov r0, #09h

savedata: lcall star

lcall delay

mov a, r1

cjne a, #0ffh, save1

mov a, r0

mov r1, a

ljmp checkpw

save1: mov a, r2

cjne a, #0ffh, save2

mov a, r0

mov r2, a

ljmp checkpw

save2: mov a, r3

cjne a, #0ffh, checkpw

mov a, r0

36

mov r3, a

ljmp checkpw

compare: mov a, r1

cjne a, #03h, lcdinvalid

mov a, r2

cjne a, #05h, lcdinvalid

mov a, r3

cjne a, #01h, lcdinvalid

ret

lcdinvalid: mov a, #80h

lcall cmdw

lcall delay

mov a, #'I'

lcall datw

lcall delay

mov a, #'n'

lcall datw

lcall delay

mov a, #'v'

lcall datw

lcall delay

mov a, #'a'

lcall datw

lcall delay

mov a, #'l'

lcall datw

lcall delay

mov a, #'i'

lcall datw

lcall delay

mov a, #'d'

lcall datw

lcall delay

mov a, #' '

lcall datw

lcall delay

37

mov a, #'P'

lcall datw

lcall delay

mov a, #'a'

lcall datw

lcall delay

mov a, #'s'

lcall datw

lcall delay

mov a, #'s'

lcall datw

lcall delay

mov a, #'w'

lcall datw

lcall delay

mov a, #'o'

lcall datw

lcall delay

mov a, #'r'

lcall datw

lcall delay

mov a, #'d'

lcall datw

lcall delay

setb p0.7

lcall delayb

lcall delayb

lcall delayb

clr p0.7

ret

vpss: mov a, #80h

lcall cmdw

lcall delay

mov a, #'v'

lcall datw

lcall delay

38

mov a, #'a'

lcall datw

lcall delay

mov a, #'l'

lcall datw

lcall delay

mov a, #'i'

lcall datw

lcall delay

mov a, #'d'

lcall datw

lcall delay

mov a, #' '

lcall datw

lcall delay

mov a, #'P'

lcall datw

lcall delay

mov a, #'a'

lcall datw

lcall delay

mov a, #'s'

lcall datw

lcall delay

mov a, #'s'

lcall datw

lcall delay

mov a, #'w'

lcall datw

lcall delay

mov a, #'o'

lcall datw

lcall delay

mov a, #'r'

lcall datw

lcall delay

39

mov a, #'d'

lcall datw

lcall delay

smotor: mov r6, #03h

mtrf: mov p0, #09h

lcall delayn

mov p0, #0ch

lcall delayn

mov p0, #06h

lcall delayn

mov p0, #03h

lcall delayn

djnz r6, mtrf

lcall delayb

lcall delayb

lcall delayb

mov r6, #03h

mtrr: mov p0, #03h

lcall delayn

mov p0, #06h

lcall delayn

mov p0, #0ch

lcall delayn

mov p0, #09h

lcall delayn

djnz r6, mtrr

mov p0, #00h

lcall delay

ret

star: mov a, #'*'

lcall datw

lcall delayb

ret

cmdw: mov p1, a

clr p2.3

clr p2.4

40

setb p2.5

lcall delay

clr p2.5

ret

datw: mov p1, a

setb p2.3

clr p2.4

setb p2.5

lcall delay

clr p2.5

ret

delayb: mov r7, #05h

back13:mov r4, #0ffh

back11:mov r5, #0ffh

back12:djnz r5, back12

djnz r4, back11

djnz r7, back13

ret

delay: mov r4, #22h

back1: mov r5, #0ffh

back: djnz r5, back

djnz r4, back1

ret

delayn: mov r4, #0ffh

bac: mov r5, #0ffh

ba: djnz r5, ba

djnz r4, bac

ret

end

5.4 CIRCUIT DIAGRAM

41

Fig-5.3-circuit diagram of password based door locking system

5.5 Applications

Home:

Home security is top priority of all concerned. Today there are plenty of home

security products to ensure your family’s security completely. Home security is the

most significant one for every homeowner either in an individual house or an

apartment. To get the absolute peace of mind whether you are at first time home or

out of home you must ensure that your home is installed with the perfect home

security monitoring system. Home security system using PASSWORD PROTECTED

DOOR LOCKING SYSTEM is the best way to protect your family and your

belongings. People engaged in business and often going on a business or personal trip

is at the maximum need. .

Safes:

42

A security system without a high security safe is not a complete theft prevention

system. Throughout history there has been an enduring need to protect irreplaceable

possessions from theft . In the Middle Ages merchants constructed treasury safes

made of oak conjoined with iron as a repository of security. With technological

advances, today's safes have tempered steel walls with fire-retardant material

interspersed within the walls, affording a deterrent to theft , unimaginable just a

century ago. Only safes can provide a superior level of protection for documents,

jewelry, guns and personal items. A security safe based on PASSWORD

PROTECTED DOOR LOCKING SYSTEM designed for specific needs can meet

the varied necessities of home, business and office requirements. Security safes are

an essential protection against theft.

Vehicles:

Nine-out-of-ten cars are hot-wired and driven away. Mechanical devices such as

steering wheel bars and pedal locks are only a minor inconvenience for the

professional. Although they may work as a deterrent, car alarms can be "hot wired"

around. The professional thief simply cuts or jumps the alarm wires and he is gone.

Tracking devices used by police to locate stolen cars do not STOP the vehicle from

being hot-wired and driven away. They depend on early notification of authorities by

the owner. A car that is taken at 2 a.m. can be dismantled miles away before the

owner even realizes it is gone. Although the PASSWORD PROTECTED DOOR

LOCKING SYSTEM can defeat most tactical attempts made by the thief and can be

regarded as the safest means of security.

5.6 CONCLUSION

PASSWORD PROTECTED DOOR LOCKING SYSTEM is an access control

system that allows only authorized person to access the restricted area. This provides

us with intense safety and security at various levels of livelihood. Some of them

include houses, offices, institutions, car locking system, safes. Some of its important

features are

a) Easily affordable means of security

b) Low power consumption

43

c) Easy to install

d) Easily compatible product.

REFERENCES

1. www.8051projects.net

2. www.datasheet.in

3. www.microchip.com

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