INDEX

1. Abbreviations

2. Figures locations

3. Introduction

4. Block Diagram

4.1Block Diagram Description

5. Schematic

5.1Schematic Description

6. Hardware Components

6.1 Power supply6.2 Microcontroller

6.3 LCD

6.4 relay

6.5 key pad or mobile phone

7. Software components

7.1 Embedded ‘C’

7.2 Keil u vision

7.3 Express pcb

8. Source code9. Conclusion

10. Future Aspects

11. Bibliography

1. ABBREVIATIONS

Symbol Name

ACC Accumulator

B B register

PSW Program status word

SP Stack pointer

DPTR Data pointer 2 bytes

DPL Low byte

DPH High byte

P0 Port0

P1 Port1

P2 Port2

P3 Port3

IP Interrupt priority control

IE Interrupt enable control

TMOD Timer/counter mode control

TCON Timer/counter control

T2CON Timer/counter 2 control

T2MOD Timer/counter mode2 control

TH0 Timer/counter 0high byte

TL0 Timer/counter 0 low byte

TH1 Timer/counter 1 high byte

TL1 Timer/counter 1 low byte

TH2 Timer/counter 2 high byte

TL2 Timer/counter 2 low byte

SCON Serial control

SBUF Serial data buffer

2.FIGURE LOCATIONS

S.No. Figure Page No.

1 Block diagram

2 Schematic Diagram

3 Power Supply

5 Wave forms of Rectifier

6 Smoothing Capacitors

7 Internal Block Diagram of power supply

8 Architecture of 8052

9 Oscillator connections

10 TCON Register

11 TMOD Register

12 Schematic diagram of lcd

1316*2 alphanumeric lcd module specifications

14 Address locations for a 1*16 line lcd

15 Block diagram of lcd

16 Power supply of lcd

17 Pin diagram of 1*16 lines lcd

18 Pin specifications

19 Character details in lcd

20 Flow chart of lcd

26 4*4 keypad

ABSTRACT

Advanced Security System using mobiles

Aim:

The main aim of the project is to provide security to any system using DTMF technology.

Description:

Here I’m going to controlling two

devices (Fan and Bulb) using 8051uC

kit, Relays, DTMF and two mobile

phones. The uC kit is connected to Fan

and Bulb through relays.And the relays

are controlled by uC. The control signals

are send to uC using mobile phone

through DTMF circuit.

My first mobile connected to my kit

and second mobile is used to send

DTMFDTMF: DTMF stands for Dual-Tone-Multi-Frequency. DTMF is used for telecommunication signaling over analog telephone lines in the voice frequency band between telephone handsets and other communication devices and the switching center.

DTMF is used for tone dialing using push buttons

whenever we press push buttons on telephone handsets two pre assigned frequencies will transmit and we can assign some functionality to that key or group of keys by which can control remote devices using DTMF.

password to mobile phone1.Pre defined password is set to fan and bulb whenever the password

matches the on/off switches are operated.

CHAPTER-1

EMBEDDED SYSTEMS

Introduction:

An embedded system is a system which is going to do a predefined specified task is the

embedded system and is even defined as combination of both software and hardware. A general-

purpose definition of embedded systems is that they are devices used to control, monitor or assist

the operation of equipment, machinery or plant. "Embedded" reflects the fact that they are an

integral part of the system. At the other extreme a general-purpose computer may be used to

control the operation of a large complex processing plant, and its presence will be obvious.

All embedded systems are including computers or microprocessors. Some of these

computers are however very simple systems as compared with a personal computer.

The very simplest embedded systems are capable of performing only a single function or

set of functions to meet a single predetermined purpose. In more complex systems an application

program that enables the embedded system to be used for a particular purpose in a specific

application determines the functioning of the embedded system. The ability to have programs

means that the same embedded system can be used for a variety of different purposes. In some

cases a microprocessor may be designed in such a way that application software for a particular

purpose can be added to the basic software in a second process, after which it is not possible to

make further changes. The applications software on such processors is sometimes referred to as

firmware.

The simplest devices consist of a single microprocessor (often called a "chip”), which may itself be packaged with other chips in a hybrid system or Application Specific Integrated

Circuit (ASIC). Its input comes from a detector or sensor and its output goes to a switch or activator which (for example) may start or stop the operation of a machine or, by operating a valve, may control the flow of fuel to an engine.

As the embedded system is the combination of both software and hardware

Figure: Block diagram of Embedded System

Software deals with the languages like ALP, C, and VB etc., and Hardware deals with Processors, Peripherals, and Memory.

Memory: It is used to store data or address.

Peripherals: These are the external devices connected

Processor: It is an IC which is used to perform some task

Applications of embedded systems

Manufacturing and process control

Construction industry

Transport

Buildings and premises

Domestic service

Embedded

System

Software Hardware

ALP

C

VB Etc.,

Processor

Peripherals

memory

Communications

Office systems and mobile equipment

Banking, finance and commercial

Medical diagnostics, monitoring and life support

Testing, monitoring and diagnostic systems

Processors are classified into four types like:

Micro Processor (µp)

Micro controller (µc)

Digital Signal Processor (DSP)

Application Specific Integrated Circuits (ASIC)

Micro Processor (µp):

A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.

Three basic characteristics differentiate microprocessors:

Instruction set : The set of instructions that the microprocessor can execute.

Bandwidth : The number of bits processed in a single instruction.

Clock speed : Given in megahertz (MHz), the clock speed determines how many instructions

per second the processor can execute.

In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz. In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer).

A microprocessor has three basic elements, as shown above. The ALU performs all arithmetic computations, such as addition, subtraction and logic operations (AND, OR, etc). It is controlled by the Control Unit and receives its data from the Register Array.   The Register Array is a set of registers used for storing data. These registers can be accessed by the ALU very quickly. Some registers have specific functions - we will deal with these later.   The Control Unit controls the entire process. It provides the timing and a control signal for getting data into and out of the registers and the ALU and it synchronizes the execution of instructions (we will deal with instruction execution at a later date).  

Three Basic Elements of a Microprocessor

Micro Controller (µc):

A microcontroller is a small computer on a single integrated circuit containing a processor core,

memory, and programmable input/output peripherals. Program memory in the form of NOR

flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM.

Microcontrollers are designed for embedded applications, in contrast to the microprocessors

used in personal computers or other general purpose applications.

Figure: Block Diagram of Micro Controller (µc)

Timer, Counter, serial communication ROM, ADC, DAC, Timers, USART, Oscillators

Etc.,

ALU

CU

Memory

Digital Signal Processors (DSPs):

Digital Signal Processors is one which performs scientific and mathematical operation.

Digital Signal Processor chips - specialized microprocessors with architectures designed

specifically for the types of operations required in digital signal processing. Like a general-

purpose microprocessor, a DSP is a programmable device, with its own native instruction code.

DSP chips are capable of carrying out millions of floating point operations per second, and like

their better-known general-purpose cousins, faster and more powerful versions are continually

being introduced. DSPs can also be embedded within complex "system-on-chip" devices, often

containing both analog and digital circuitry.

Application Specific Integrated Circuit (ASIC)

ASIC is a combination of digital and analog circuits packed into an IC to achieve the desired control/computation function

ASIC typically contains

CPU cores for computation and control

Peripherals to control timing critical functions

Memories to store data and program

Analog circuits to provide clocks and interface to the real world which is analog in nature

I/Os to connect to external components like LEDs, memories, monitors etc.

Computer Instruction Set

There are two different types of computer instruction set there are:

1. RISC (Reduced Instruction Set Computer) and

2. CISC (Complex Instruction Set computer)

Reduced Instruction Set Computer (RISC)

A RISC (reduced instruction set computer) is a microprocessor that is designed to perform a smaller number of types of computer instruction so that it can operate at a higher speed (perform more million instructions per second, or millions of instructions per second). Since each instruction type that a computer must perform requires additional transistors and circuitry, a larger list or set of computer instructions tends to make the microprocessor more complicated and slower in operation.

Besides performance improvement, some advantages of RISC and related design improvements are:

A new microprocessor can be developed and tested more quickly if one of its aims is to be less

complicated.

Operating system and application programmers who use the microprocessor's instructions will

find it easier to develop code with a smaller instruction set.

The simplicity of RISC allows more freedom to choose how to use the space on a

microprocessor.

Higher-level language compilers produce more efficient code than formerly because they have always tended to use the smaller set of instructions to be found in a RISC computer.

RISC characteristics

Simple instruction set:

In a RISC machine, the instruction set contains simple, basic instructions, from which more

complex instructions can be composed.

Same length instructions.

Each instruction is the same length, so that it may be fetched in a single operation.

1 machine-cycle instructions.

Most instructions complete in one machine cycle, which allows the processor to handle several

instructions at the same time. This pipelining is a key technique used to speed up RISC

machines.

Complex Instruction Set Computer (CISC)

CISC, which stands for Complex Instruction Set Computer, is a philosophy for designing chips that are easy to program and which make efficient use of memory. Each instruction in a CISC instruction set might perform a series of operations inside the processor. This reduces the number of instructions required to implement a given program, and allows the programmer to learn a small but flexible set of instructions.

The advantages of CISCAt the time of their initial development, CISC machines used available technologies to optimize computer performance.

Microprogramming is as easy as assembly language to implement, and much less expensive than

hardwiring a control unit.

The ease of micro-coding new instructions allowed designers to make CISC machines upwardly

compatible: a new computer could run the same programs as earlier computers because the new

computer would contain a superset of the instructions of the earlier computers.

As each instruction became more capable, fewer instructions could be used to implement a given

task. This made more efficient use of the relatively slow main memory.

Because micro program instruction sets can be written to match the constructs of high-level

languages, the compiler does not have to be as complicated.

The disadvantages of CISCStill, designers soon realized that the CISC philosophy had its own problems, including:

Earlier generations of a processor family generally were contained as a subset in every new

version --- so instruction set & chip hardware become more complex with each generation of

computers.

So that as many instructions as possible could be stored in memory with the least possible wasted

space, individual instructions could be of almost any length---this means that different

instructions will take different amounts of clock time to execute, slowing down the overall

performance of the machine.

Many specialized instructions aren't used frequently enough to justify their existence ---

approximately 20% of the available instructions are used in a typical program.

CISC instructions typically set the condition codes as a side effect of the instruction. Not only

does setting the condition codes take time, but programmers have to remember to examine the

condition code bits before a subsequent instruction changes them.

Memory Architecture

There two different type’s memory architectures there are:

Harvard Architecture

Von-Neumann Architecture

Harvard Architecture

Computers have separate memory areas for program instructions and data. There are two or more internal data buses, which allow simultaneous access to both instructions and data. The CPU fetches program instructions on the program memory bus.

The Harvard architecture is a computer architecture with physically separate storage and signal pathways for instructions and data. The term originated from the Harvard Mark I relay-based computer, which stored instructions on punched tape (24 bits wide) and data in electro-mechanical counters. These early machines had limited data storage, entirely contained within the central processing unit, and provided no access to the instruction storage as data. Programs needed to be loaded by an operator, the processor could not boot itself.

Figure: Harvard Architecture

Modern uses of the Harvard architecture

The principal advantage of the pure Harvard architecture - simultaneous access to more than one

memory system - has been reduced by modified Harvard processors using modern CPU cache

systems. Relatively pure Harvard architecture machines are used mostly in applications where

tradeoffs, such as the cost and power savings from omitting caches, outweigh the programming

penalties from having distinct code and data address spaces.

Digital signal processors (DSPs) generally execute small, highly-optimized audio or video

processing algorithms. They avoid caches because their behavior must be extremely

reproducible. The difficulties of coping with multiple address spaces are of secondary concern to

speed of execution. As a result, some DSPs have multiple data memories in distinct address

spaces to facilitate SIMD and VLIW processing. Texas Instruments TMS320 C55x processors,

as one example, have multiple parallel data busses (two write, three read) and one instruction

bus.

Microcontrollers are characterized by having small amounts of program (flash memory) and data

(SRAM) memory, with no cache, and take advantage of the Harvard architecture to speed

processing by concurrent instruction and data access. The separate storage means the program

and data memories can have different bit depths, for example using 16-bit wide instructions and

8-bit wide data. They also mean that instruction pre-fetch can be performed in parallel with other

activities. Examples include, the AVR by Atmel Corp, the PIC by Microchip Technology, Inc.

and the ARM Cortex-M3 processor (not all ARM chips have Harvard architecture).

Even in these cases, it is common to have special instructions to access program memory as data

for read-only tables, or for reprogramming.

Von-Neumann Architecture

A computer has a single, common memory space in which both program instructions and data are stored. There is a single internal data bus that fetches both instructions and data. They cannot be performed at the same time

The von Neumann architecture is a design model for a stored-program digital computer that uses a central processing unit (CPU) and a single separate storage structure ("memory") to hold both instructions and data. It is named after the mathematician and early computer scientist John von Neumann. Such computers implement a universal Turing machine and have a sequential architecture.

A stored-program digital computer is one that keeps its programmed instructions, as well as its data, in read-write, random-access memory (RAM). Stored-program computers were advancement over the program-controlled computers of the 1940s, such as the Colossus and the ENIAC, which were programmed by setting switches and inserting patch leads to route data and to control signals between various functional units. In the vast majority of modern computers, the same memory is used for both data and program instructions. The mechanisms for transferring the data and instructions between the CPU and memory are, however, considerably more complex than the original von Neumann architecture.

The terms "von Neumann architecture" and "stored-program computer" are generally used interchangeably, and that usage is followed in this article.

Figure: Schematic of the Von-Neumann Architecture.

Basic Difference between Harvard and Von-Neumann Architecture

The primary difference between Harvard architecture and the Von Neumann architecture is in

the Von Neumann architecture data and programs are stored in the same memory and managed

by the same information handling system.

Whereas the Harvard architecture stores data and programs in separate memory devices and they

are handled by different subsystems.

In a computer using the Von-Neumann architecture without cache; the central processing unit

(CPU) can either be reading and instruction or writing/reading data to/from the memory. Both of

these operations cannot occur simultaneously as the data and instructions use the same system

bus.

In a computer using the Harvard architecture the CPU can both read an instruction and access

data memory at the same time without cache. This means that a computer with Harvard

architecture can potentially be faster for a given circuit complexity because data access and

instruction fetches do not contend for use of a single memory pathway.

Today, the vast majority of computers are designed and built using the Von Neumann

architecture template primarily because of the dynamic capabilities and efficiencies gained in

designing, implementing, operating one memory system as opposed to two. Von Neumann

architecture may be somewhat slower than the contrasting Harvard Architecture for certain

specific tasks, but it is much more flexible and allows for many concepts unavailable to Harvard

architecture such as self programming, word processing and so on.

Harvard architectures are typically only used in either specialized systems or for very specific

uses. It is used in specialized digital signal processing (DSP), typically for video and audio

processing products. It is also used in many small microcontrollers used in electronics

applications such as Advanced RISK Machine (ARM) based products for many vendors.

CHAPTER-2

OVERVIEW OF PROJECT

The advanced security system architecture we proposed contains many subsystems. Here we are using 8051 microcontroller kit to interface two devices (bulb and fan for home appliances) and other is mobile phone-1.When we give commands from mobile phone-2 to phone-1 the controller kit receives the commands and performs the operation (whether bulb on or off) . The operation is depending on the command getting into the uC.

The application is not only restricted to remote operation, it operate directly also, like we are at home then we will give commands directly through the keypad to the microcontroller kit for switching the devices at home with a security code. .

Block Diagram

Power Supply:

Hardware Implementation:

POWER SUPPLY :

A device or system that supplies electrical or other types of energy to an output load or group of

loads is called a power supply unit or PSU. The term is most commonly applied to electrical

energy supplies, less often to mechanical ones, and rarely to others. Power supply generates the

required voltage by using the transformer, bridge rectifier, filter and voltage regulator. Here we

giving 5v to the micro controller.

MICROCONTROLLER:

The microcontroller is the heart of the proposed embedded system. The controller used is a low

power, cost efficient chip manufactured by ATMEL having 8K bytes of on-chip flash memory.

DTMF(Dual Tone Multiple Frequency):

Dual-Tone Multi-Frequency (DTMF) signaling is a standard telecommunication system. In this

system, a matrix is used to compose a signal, which consists of a lower frequency group

containing four distinguished frequencies which are below 1 KHz and a high frequency group

also containing four distinguished frequencies which are above 1 KHz (figure 2). Each telephone

key contains a pair of simultaneous low and high frequency tones.

RELAYA relay is an electrically operated switch. Current flowing through the coil of the relay creates

a magnetic field which attracts a lever and changes the switch contacts.

Software used:

Keil uVision Embedded C Express PCB

KEIL Software

Installing the Keil software on a Windows PC

Insert the CD-ROM in your computer’s CD drive

On most computers, the CD will “auto run”, and you will see the Keil installation menu. If the

menu does not appear, manually double click on the Setup icon, in the root directory: you will

then see the Keil menu.

On the Keil menu, please select “Install Evaluation Software”. (You will not require a license

number to install this software).

Follow the installation instructions as they appear.

Configuring the Simulator

Open the Keil Vision2

Go to Project – Open Project and browse for Hello in Ch03_00 in Pont and open it.

Go to Project – Select Device for Target ‘Target1’

Select 8052(all variants) and click OK

Now we need to check the oscillator frequency:

Go to project – Options for Target ‘Target1’

Make sure that the oscillator frequency is 12MHz.

Building the Target

Build the target as illustrated in the figure below

Running the Simulation

Having successfully built the target, we are now ready to start the debug session and run the simulator.

First start a debug session

The flashing LED we will view will be connected to Port 1. We therefore want to observe the activity on this port

To ensure that the port activity is visible, we need to start the ‘periodic window update’ flag

Go to Debug - Go

While the simulation is running, view the performance analyzer to check the delay durations.

Go to Debug – Performance Analyzer and click on it

Double click on DELAY_LOOP_Wait in Function Symbols: and click Define button

CHAPTER-3

MICROCONTROLLER

Microcontroller

Description of Microcontroller 89S52:

The AT89S52 is a low-power, high-performance CMOS 8-bit micro controller with

8Kbytes of in-system programmable flash memory. The device is manufactured

Using Atmel’s high-density nonvolatile memory technology and is compatible with the

industry-standard 80C51 micro controller. The on-chip Flash allows the program memory to be

reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a

versatile 8-bit CPU with in-system programmable flash one monolithic http; the Atmel AT89S52

is a powerful micro controller, which provides a highly flexible and cost effective solution to any

cost effective solution to any embedded control applications to any embedded control

applications

The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM,

32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, full duplex serial

port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static

logic for operation down to zero frequency and supports two software selectable power saving

modes. The Idle Mode stops the CPU while allowing the RAM timer/counters, serial port, and

interrupt system to continue functioning. The Power-down mode saves the RAM contents but

freezes the oscillator, disabling all other chip functions until the next interrupt Or hardware reset.

Features:

• Compatible with MCS-51 Products

• 8K Bytes of In-System Programmable (ISP) Flash Memory

– Endurance: 1000 Write/Erase Cycles

• 4.0V to 5.5V Operating Range

• Fully Static Operation: 0 Hz to 33 MHz

• Three-level Program Memory Lock

• 256K Internal RAM

• 32 Programmable I/O Lines

• 3 16-bit Timer/Counters

• Eight Interrupt Sources

• Full Duplex UART Serial Channel

• Low-power Idle and Power-down Modes

• Interrupt Recovery from Power-down Mode

• Watchdog Timer

• Dual Data Pointer

• Power-off Flag

Architecture of 8052:

Fig10: architecture of 8052

AT89S52:

Fig 9: pin configuration

PIN DESCRIPTION OF MICROCONTROLLER 89S52

VCC:

Supply voltage.

GND:

Ground

Port 0:

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink

eight TTL inputs. When 1’s are written to port 0 pins, the pins can be used as high impedance

inputs. Port 0 can also be configured to be the multiplexed low order address/data bus during

accesses to external program and data memory. In this mode, P0 has internal pull-ups.Port 0 also

receives the code bytes during Flash Programming and outputs the code bytes during program

verification. External pull-ups are required during program verification

Port 1:

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 Output buffers can

sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the

internal pull-ups and can be used as inputs. In

addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input(P1.0/T2)

and the timer/counter 2 trigger input P1.1/T2EX), respectively, as shown in the following table.

Port 1 also receives the low-order address bytes during Flash programming and verification.

Port 2:

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers can

sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the

internal pull-ups and can be used as inputs. Port 2 emits the high-order address byte during

fetches from external program memory and during accesses to external data memory that use 16-

bit addresses (MOVX @DPTR). In this application, Port 2 uses strong internal pull-ups when

emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI),

Port 2emits the contents of the P2 Special

Function Register. Port 2 also receives the high-order address bits and some control signals

during Flash programming and verification

Port 3:

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are writ 1s are written to Port 3 pins, they are pulled high

by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being

pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of

various special features of the AT89S52, as shown in the following table.

Port 3 also receives some control signals for Flash programming and verification.

RST:

Reset input. A high on this pin for two machine cycles while the oscillator is running resets

the device.

ALE/PROG:

Address Latch Enable (ALE) 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 of1/6 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 micro controller is in external execution mode.

PSEN:

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

AT89S52 is executing code from external program memory, PSEN is activated twice each

machine cycle, except that two PSEN activations are skipped during each access to external data

memory.

EA/VPP:

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. A should be

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

enables voltage (VPP) during Flash programming.

XTAL1:

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

XTAL2:

Output from the inverting oscillator amplifier. Oscillator Characteristics:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator, as shown in Figure 1. 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, as shown in Figure

2.

Figure 11:. Oscillator Connections

Special Function Register (SFR) Memory: -

Special Function Registers (SFR s) are areas of memory that control specific

functionality of the 8051 processor. For example, four SFRs permit access to the 8051’s 32

input/output lines. Another SFR allows the user to set the serial baud rate, control and access

timers, and configure the 8051’s interrupt system.

The Accumulator: The Accumulator, as its name suggests is used as a general register to

accumulate the results of a large number of instructions. It can hold 8-bit (1-byte) value and is

the most versatile register.

The “R” registers: The “R” registers are a set of eight registers that are named R0, R1. Etc up to

R7. These registers are used as auxiliary registers in many operations.

The “B” registers: The “B” register is very similar to the accumulator in the sense that it may

hold an 8-bit (1-byte) value. Two only uses the “B” register 8051 instructions: MUL AB and

DIV AB.

The Data Pointer: The Data pointer (DPTR) is the 8051’s only user accessible 16-bit (2Bytes)

register. The accumulator, “R” registers are all 1-Byte values. DPTR, as the name suggests, is

used to point to data. It is used by a number of commands, which allow the 8051 to access

external memory.

THE PROGRAM COUNTER AND STACK POINTER:

The program counter (PC) is a 2-byte address, which tells the 8051 where the next

instruction to execute is found in memory. The stack pointer like all registers except DPTR and

PC may hold an 8-bit (1-Byte) value

ADDRESSING MODES:

An “addressing mode” refers that you are addressing a given memory location. In

summary, the addressing modes are as follows, with an example of each:

Each of these addressing modes provides important flexibility.

Immediate Addressing MOV A, #20 H

Direct Addressing MOV A, 30 H

Indirect Addressing MOV A, @R0

Indexed Addressing

a. External Direct MOVX A, @DPTR

b. Code In direct MOVC A, @A+DPTR

Immediate Addressing:

Immediate addressing is so named because the value to be stored in memory immediately follows the operation code in memory. That is to say, the instruction itself dictates what value will be stored in memory.

For example, the instruction:

MOV A, #20H:

This instruction uses immediate Addressing because the accumulator will be loaded

with the value that immediately follows in this case 20(hexadecimal). Immediate addressing is

very fast since the value to be loaded is included in the instruction. However, since the value to

be loaded is fixed at compile-time it is not very flexible.

Direct Addressing:

Direct addressing is so named because the value to be stored in memory is obtained by

directly retrieving it from another memory location.

For example:

MOV A, 30h

This instruction will read the data out of internal RAM address 30(hexadecimal) and store

it in the Accumulator. Direct addressing is generally fast since, although the value to be loaded

isn’t included in the instruction, it is quickly accessible since it is stored in the 8051’s internal

RAM. It is also much more flexible than Immediate Addressing since the value to be loaded is

whatever is found at the given address which may variable.

Also it is important to note that when using direct addressing any instruction that refers

to an address between 00h and 7Fh is referring to the SFR control registers that control the 8051

micro controller itself.

Indirect Addressing:

Indirect addressing is a very powerful addressing mode, which in many cases provides

an exceptional level of flexibility. Indirect addressing is also the only way to access the extra 128

bytes of internal RAM found on the 8052. Indirect addressing appears as follows:

MOV A, @R0:

This instruction causes the 8051 to analyze Special Function Register (SFR)

Memory.

Special Function Registers (SFRs) are areas of memory that control specific functionality of

the 8051 processor. For example, four SFRs permit access to the 8051’s 32 input/output lines.

Another SFR allows the user to set the serial baud rate, control and access timers, and configure

the 8051’s interrupt system.

Timer 2 Registers:

Control and status bits are contained in registers T2CON and T2MOD for Timer 2.

The register pair (RCAP2H , RCAP2L) are the Capture / Reload registers for Timer 2 in

16-bit capture mode or 16-bit auto-reload mode .

Interrupt Registers:

The individual interrupt enable bits are in the IE register . Two priorities can be

set for each of the six interrupt sources in the IP register.

Timer 2:

Timer 2:

Timer 2 is a 16-bit Timer / Counter that can operate as either a timer or an event

counter. The type of operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has

three operating Modes : capture , auto-reload ( up or down Counting ) , and baud rate

generator . The modes are selected by bits in T2CON. Timer2 consists of two 8-bit registers,

TH2 and TL2. In the Timer function, the TL2 register is incremented every machine cycle.

Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the

oscillator frequency.

In the Counter function , the register is incremented in response to a 1-to-0

transition at its corresponding external input pin , T2 .When the samples show a high in

one cycle and a low in the next cycle, the count is incremented . Since two machine cycles

(24 Oscillator periods ) are required to recognize 1-to-0 transition , the maximum count

rate is 1 / 24 of the oscillator frequency .

To ensure that a given level is sampled at least once before it changes , the level

should be held for at least one full machine cycle.

Baud Rate Generator:

Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK

in T2CON . Note that the baud rates for transmit and receive can be different if Timer

2 is used for the receiver or transmitter and Timer 1 is used for the other function .The

baud rates in Modes 1 and 3 are determined by Timer 2’s overflow rate according to the

following equation .

Modes 1 and 3 Baud Rates =Timer 2 Overflow Rate

16

The timer operation is different for Timer 2 when it is used as a baud rate

generator .Normally ,as a timer , it increments every machine cycle (at 1/12 the oscillator

frequency).As a baud rate generator , however, it increments every state time ( at 1/2 the

oscillator frequency ) .

Timer 0:

Timer 0 functions as either a timer or event counter in four modes of operation .

Timer 0 is controlled by the four lower bits of the TMOD register and bits 0, 1, 4 and 5

of the TCON register. Mode 0 ( 13-bit Timer) Mode 0 configures timer 0 as a 13-bit

timer which is set up as an 8-bit timer (TH0 register) with a modulo 32 prescaler

implemented with the lower five bits of the TL0 register . The upper three bits of TL0

register are indeterminate and should be ignored. Prescaler overflow increments the

TH0 register. Mode 1 ( 16-bit Timer )Mode 1 is the same as Mode 0, except that the

Timer register is being run with all 16 bits .

Mode 1 configures timer 0 as a 16-bit timer with the TH0 and TL0 registers

connected in cascade. The selected input increments the TL0 register. Mode 2 (8-bit

Timer with Auto-Reload)Mode 2 configures timer 0 as an 8-bit timer ( TL0 register )

that automatically reloads from the TH0 register . TL0 overflow sets TF0 flag in the

TCON register and reloads TL0 with the contents of TH0, which is preset by

software. Mode 3 ( Two 8-bit Timers )Mode 3 configures timer 0 so that registers TL0

and TH0 operate as separate 8-bit timers. This mode is provided for applications requiring

an additional 8-bit timer or counter.

Timer 1:

Timer 1 is identical to timer 0, except for mode 3, which is a hold-count mode.

Mode 3 (Halt) Placing Timer 1 in mode 3 causes it to halt and hold its count. This can

be used to halt Timer 1 when TR1 run control bit is not available i.e., when Timer 0

is in mode 3.

Baud Rates:

The baud rate in Mode 0 is fixed. The baud rate in Mode 2 depends on the

value of bit SMOD in Special Function Register PCON. If SMOD = 0 (which is its

value on reset), the baud rate is 1/64 the oscillator frequency. If SMOD = 1, the baud

rate is 1/32 the oscillator frequency. In the 89S52, the baud rates in Modes 1 and 3 are

determined by the Timer 1 overflow rate. In case of Timer 2 , these baud rates can

be determined by Timer 1 , or by Timer 2 , or by both (one for transmit and the other for

receive ).

Fig 12: TCON REGISTER: Timer/counter Control Register

Fig 13:TMOD REGISTER: Timer/Counter 0 and 1 Modes

Power Supply:

Power supply is a reference to a source of electrical power. A device or system that supplies

electrical or other types of energy to an output load or group of loads is called a power supply unit or

PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones,

and rarely to others.

This power supply section is required to convert AC signal to DC signal and also to reduce the

amplitude of the signal. The available voltage signal from the mains is 230V/50Hz which is an AC

voltage, but the required is DC voltage (no frequency) with the amplitude of +5V and +12V for various

applications.

In this section we have Transformer, Bridge rectifier, are connected serially and voltage regulators

for +5V and +12V (7805 and 7812) via a capacitor (1000µF) in parallel are connected parallel as

shown in the circuit diagram below. Each voltage regulator output is again is connected to the

capacitors of values (100µF, 10µF, 1 µF, 0.1 µF) are connected parallel through which the

corresponding output (+5V or +12V) are taken into consideration.

Fig3: power supply diagram

Circuit Explanation:

A) Transformer:

A transformer is a device that transfers electrical energy from one circuit to another through

inductively coupled electrical conductors. A changing current in the first circuit (the primary)

creates a changing magnetic field; in turn, this magnetic field induces a changing voltage in the

second circuit (the secondary). By adding a load to the secondary circuit, one can make current

flow in the transformer, thus transferring energy from one circuit to the other.

The secondary induced voltage VS, of an ideal transformer, is scaled from the primary VP by a

factor equal to the ratio of the number of turns of wire in their respective windings:

Basic principle :

The transformer is based on two principles: firstly, that an electric current can produce a

magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of

wire induces a voltage across the ends of the coil (electromagnetic induction). By changing the

current in the primary coil, it changes the strength of its magnetic field; since the changing

magnetic field extends into the secondary coil, a voltage is induced across the secondary.

A simplified transformer design is shown below. A current passing through the primary

coil creates a magnetic field. The primary and secondary coils are wrapped around a core of very

high magnetic permeability, such as iron; this ensures that most of the magnetic field lines

produced by the primary current are within the iron and pass through the secondary coil as well

as the primary coil. .An ideal step-down transformer showing magnetic flux in the core.

Induction law :

The voltage induced across the secondary coil may be calculated from Faraday's law of

induction, which states that:

Where VS is the instantaneous voltage, NS is the number of turns in the secondary

coil and Φ equals the magnetic flux through one turn of the coil. If the turns of the coil are

oriented perpendicular to the magnetic field lines, the flux is the product of the magnetic field

strength B and the area A through which it cuts. The area is constant, being equal to the cross-

sectional area of the transformer core, whereas the magnetic field varies with time according to

the excitation of the primary. Since the same magnetic flux passes through both the primary and

secondary coils in an ideal transformer, the instantaneous voltage across the primary winding

equals

Taking the ratio of the two equations for VS and VP gives the basic equation for stepping up or

stepping down the voltage

Ideal power equation:

If the secondary coil is attached to a load that allows current to flow, electrical power is

transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is perfectly

efficient; all the incoming energy is transformed from the primary circuit to the magnetic field

and into the secondary circuit. If this condition is met, the incoming electric power must equal

the outgoing power.

Pin coming = IPVP = Pout going = ISVS

Giving the ideal transformer equation

Pin-coming = IPVP = Pout-going = ISVS

Giving the ideal transformer equation

If the voltage is increased (stepped up) (VS > VP), then the current is decreased (stepped

down) (IS < IP) by the same factor. Transformers are efficient so this formula is a reasonable

approximation.

If the voltage is increased (stepped up) (VS > VP), then the current is decreased (stepped down)

(IS < IP) by the same factor. Transformers are efficient so this formula is a reasonable

approximation.

The impedance in one circuit is transformed by the square of the turns ratio. For example,

if an impedance ZS is attached across the terminals of the secondary coil, it appears to the

primary circuit to have an impedance of

This relationship is reciprocal, so that the impedance ZP of the primary circuit appears to the

secondary to be

Detailed operation:

The simplified description above neglects several practical factors, in particular the

primary current required to establish a magnetic field in the core, and the contribution to the field

due to current in the secondary circuit.

Models of an ideal transformer typically assume a core of negligible reluctance with two

windings of zero resistance. When a voltage is applied to the primary winding, a small current

flows, driving flux around the magnetic circuit of the core. The current required to create the flux

is termed the magnetizing current; since the ideal core has been assumed to have near-zero

reluctance, the magnetizing current is negligible, although still required to create the magnetic

field.

The changing magnetic field induces an electromotive force (EMF) across each

winding. Since the ideal windings have no impedance, they have no associated voltage drop, and

so the voltages VP and VS measured at the terminals of the transformer, are equal to the

corresponding EMFs. The primary EMF, acting as it does in opposition to the primary voltage, is

sometimes termed the "back EMF". This is due to Lenz's law which states that the induction of

EMF would always be such that it will oppose development of any such change in magnetic

field.

B) Bridge Rectifier:

A diode bridge or bridge rectifier is an arrangement of four diodes in a bridge

configuration that provides the same polarity of output voltage for any polarity of input voltage.

When used in its most common application, for conversion of alternating current (AC) input into

direct current (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave

rectification from a two-wire AC input, resulting in lower cost and weight as compared to a

center-tapped transformer design, but has two diode drops rather than one, thus exhibiting

reduced efficiency over a center-tapped design for the same output voltage.

Basic Operation:

When the input connected at the left corner of the diamond is positive with respect

to the one connected at the right hand corner, current flows to the right along the upper colored

path to the output, and returns to the input supply via the lower one.

Fig4.1 bridge rectifier

When the right hand corner is positive relative to the left hand corner, current flows along

the upper colored path and returns to the supply via the lower colored path.

Fig 4.2 bridge rectifier

In each case, the upper right output remains positive with respect to the lower right one.

Since this is true whether the input is AC or DC, this circuit not only produces DC power when

supplied with AC power: it also can provide what is sometimes called "reverse polarity

protection". That is, it permits normal functioning when batteries are installed backwards or DC

input-power supply wiring "has its wires crossed" (and protects the circuitry it powers against

damage that might occur without this circuit in place).

Prior to availability of integrated electronics, such a bridge rectifier was always

constructed from discrete components. Since about 1950, a single four-terminal component

containing the four diodes connected in the bridge configuration became a standard commercial

component and is now available with various voltage and current ratings.

Fig 5: wave forms of rectifier

C) Output smoothing (Using Capacitor):

For many applications, especially with single phase AC where the full-wave bridge serves to

convert an AC input into a DC output, the addition of a capacitor may be important because the

bridge alone supplies an output voltage of fixed polarity but pulsating magnitude (see diagram

above).

Fig 6: smoothing capacitor

The function of this capacitor, known as a reservoir capacitor (aka smoothing

capacitor) is to lessen the variation in (or 'smooth') the rectified AC output voltage waveform

from the bridge. One explanation of 'smoothing' is that the capacitor provides a low impedance

path to the AC component of the output, reducing the AC voltage across, and AC current

through, the resistive load. In less technical terms, any drop in the output voltage and current of

the bridge tends to be cancelled by loss of charge in the capacitor.

This charge flows out as additional current through the load. Thus the change of load current and

voltage is reduced relative to what would occur without the capacitor. Increases of voltage

correspondingly store excess charge in the capacitor, thus moderating the change in output

voltage / current. Also see rectifier output smoothing.

The simplified circuit shown has a well deserved reputation for being dangerous, because, in

some applications, the capacitor can retain a lethal charge after the AC power source is

removed. If supplying a dangerous voltage, a practical circuit should include a reliable way to

safely discharge the capacitor

If the normal load cannot be guaranteed to perform this function, perhaps because

it can be disconnected, the circuit should include a bleeder resistor connected as close as

practical across the capacitor. This resistor should consume a current large enough to discharge

the capacitor in a reasonable time, but small enough to avoid unnecessary power waste.

Because a bleeder sets a minimum current drain, the regulation of the circuit, defined as

percentage voltage change from minimum to maximum load, is improved. However in many

cases the improvement is of insignificant magnitude.

The capacitor and the load resistance have a typical time constant τ = RC where

C and R are the capacitance and load resistance respectively. As long as the load resistor is large

enough so that this time constant is much longer than the time of one ripple cycle, the above

configuration will produce a smoothed DC voltage across the load.

In some designs, a series resistor at the load side of the capacitor is added. The smoothing can

then be improved by adding additional stages of capacitor–resistor pairs, often done only for sub-

supplies to critical high-gain circuits that tend to be sensitive to supply voltage noise.

The idealized waveforms shown above are seen for both voltage and current when

the load on the bridge is resistive. When the load includes a smoothing capacitor, both the

voltage and the current waveforms will be greatly changed. While the voltage is smoothed, as

described above, current will flow through the bridge only during the time when the input

voltage is greater than the capacitor voltage. For example, if the load draws an average current of

n Amps, and the diodes conduct for 10% of the time, the average diode current during

conduction must be 10n Amps. This non-sinusoidal current leads to harmonic distortion and a

poor power factor in the AC supply.

In a practical circuit, when a capacitor is directly connected to the output of a bridge,

the bridge diodes must be sized to withstand the current surge that occurs when the power is

turned on at the peak of the AC voltage and the capacitor is fully discharged. Sometimes a small

series resistor is included before the capacitor to limit this current, though in most applications

the power supply transformer's resistance is already sufficient.

Output can also be smoothed using a choke and second capacitor. The choke tends to

keep the current (rather than the voltage) more constant. Due to the relatively high cost of an

effective choke compared to a resistor and capacitor this is not employed in modern equipment.

Some early console radios created the speaker's constant field with the current from the high

voltage ("B +") power supply, which was then routed to the consuming circuits, (permanent

magnets were considered too weak for good performance) to create the speaker's constant

magnetic field. The speaker field coil thus performed 2 jobs in one: it acted as a choke, filtering

the power supply, and it produced the magnetic field to operate the speaker.

D) Voltage Regulator :

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level.

The 78xx (also sometimes known as LM78xx) series of devices is a family of self-contained

fixed linear voltage regulator integrated circuits. The 78xx family is a very popular choice for

many electronic circuits which require a regulated power supply, due to their ease of use and

relative cheapness.

When specifying individual ICs within this family, the xx is replaced with a two-digit

number, which indicates the output voltage the particular device is designed to provide (for

example, the 7805 has a 5 volt output, while the 7812 produces 12 volts). The 78xx line is

positive voltage regulators, meaning that they are designed to produce a voltage that is positive

relative to a common ground. There is a related line of 79xx devices which are complementary

negative voltage regulators. 78xx and 79xx ICs can be used in combination to provide both

positive and negative supply voltages in the same circuit, if necessary.

78xx ICs have three terminals and are most commonly found in the TO220 form

factor, although smaller surface-mount and larger TrO3 packages are also available from some

manufacturers. These devices typically support an input voltage which can be anywhere from a

couple of volts over the intended output voltage, up to a maximum of 35 or 40

volts, and can typically provide up to around 1 or 1.5 amps of current (though smaller or larger

packages may have a lower or higher current rating).

DTMF(Dual Tone Multiple Frequency)

DTMF:

Introduction :

Dual-Tone Multi-Frequency (DTMF) signaling is a standard telecommunication system

developed by Bell Laboratories. The DTMF signaling was proposed more than 30 years ago to

replace slower pulse dialing. Many things have changed since this time, but DTMF has become

the most popular addressing and messaging tool in telecommunications, and it does not look as

though it will fade away in foreseeable future. In this system, a matrix is used to compose a

signal, which consists of a lower frequency group containing four distinguished frequencies

which are below 1 KHz and a high frequency group also containing four distinguished

frequencies which are above 1 KHz (figure 2). Each telephone key contains a pair of

simultaneous low and high frequency tones.

To detect DTMF signals by software in the digital domain, many algorithms, including

Fast Fourier Transform (FFT), Goertzel DFT, Modified Goertzel Algorithm, Non-uniform

Discrete Fourier Transform (NDFT), Sub band NDFT, and Adaptive Frequency Estimation are

proposed. The Modified Goertzel Algorithm is one of the most accurate and computing-efficient

technologies for limited frequency detection. In DTMF tone detection cases, the Goertzel

Algorithm only transforms 8 frequencies instead of perform on an entire spectrum like FFT. This

saves a lot computational resources, which is critical for lower-power processors. Its non-

complexity is easy to adapt into small MCU and DSP.

We are using M8870 IC. The M-8870 is a full DTMF Receiver that integrates both band split

filter and decoder functions into a single 18-pin DIP or SOIC package. Manufactured using

CMOS process technology, the M-8870 offers low power consumption (35 mW max) and

precise data handling. Its filter section uses switched capacitor technology for both the high and

low group filters and for dial tone rejection. Its decoder uses digital counting techniques to detect

1 2 3 A

4 5 6 B

7 8 9 C

* 0 # D

697 Hz

770 Hz

852 Hz

941Hz

1209

Hz

1336

Hz

1744

Hz

1633

Hz

Figure 2. DTMF matrix

High frequency group

Low

freq

uenc

y gr

oup

and decode all 16 DTMF tone pairs into a 4-bit code. External component count is minimized by

provision of an on-chip differential input amplifier, clock generator, and latched tri-state

interface bus. Minimal external components required include a low-cost 3.579545 MHz color

burst crystal, a timing resistor, and a timing capacitor. The M-8870-02 provides a “power-down”

option which, when enabled, drops consumption to less than 0.5 mW. The M-8870-02 can also

inhibit the decoding of fourth column digits.

MT8870 (INTEGRATED DTMF RECEIVER)

The MT8870D/MT8870D-1 monolithic DTMF receiver offers small size, low power

consumption and high performance. It is a complete DTMF (Dual Tone Multiple Frequency)

receiver integrating both the band split filter and digital decoder functions. The filter section uses

switched capacitor techniques for high and low group filters; the decoder uses digital counting

techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code. External component

count is minimized by on chip provision of a differential input amplifier, clock oscillator and

latched three-state bus interface.

Features:

• Complete DTMF Receiver

• Low power consumption

• Internal gain setting amplifier

• Adjustable guard time

• Central office quality

• Power-down mode

• Inhibit mode

• Backward compatible with MT8870C/MT8870C-1

PIN Diagram:

Pin Description:

1. IN+ : Non-Inverting Op-Amp (Input).

2. IN- : Inverting Op-Amp (Input).

3. GS : Gain Select. Gives access to output of front end differential amplifier for

Connection of feedback resistor

4. V ref : Reference Voltage (Output). Nominally VDD/2 is used to bias inputs at

Mid-rail

5. INH : Inhibit (Input). Logic high inhibits the detection of tones representing

Characters A, B, C and D. This pin input is internally pulled down.

6. PWDN : Power down (Input). Active high. Powers down the device and inhibits the

oscillator. This pin input is internally pulled down.

7. OSC1 : Clock (Input).

8. OSC2 : Clock (Output). A 3.579545 MHz crystal connected between pins OSC1 and

OSC2 completes the internal oscillator circuit.

9. VSS: Ground (Input) 0.V typical.

10. TOE : Three State Output Enable (Input). Logic high enables the outputs Q1-Q4. This

pin is pulled up internally.

Q1-Q4 : Three State Data (Output). When enabled by TOE, provide the code corresponding to

the last valid tone-pair received (see Table 1). When TOE is logic low, the data outputs are high

impedance.

15. StD : Delayed Steering (Output).Presents a logic high when a received tone-pair has

been registered and the output latch updated; returns to logic low when the voltage on St/GT falls

below VTSt.

16. ESt : Early Steering (Output). Presents logic high once the digital algorithm has

detected a valid tone pair (signal condition). Any momentary loss of signal condition will cause

ESt to return to a logic low.

17. St/GT : Steering Input/Guard time (Output) Bidirectional. A voltage greater than VTSt

detected at St Causes the device to register the detected tone pair and update the output latch. A

voltage less than VTSt free the device to accept a new tone pair. The GT output acts to reset the

external steering time-constant; its state is a function of ESt and the voltage on St.

18. VDD : Positive power supply (Input). +5V typical.

NC : No Connection.

Filter Section :

Separation of the low-group and high group tones is achieved by applying the DTMF signal to

the inputs of two sixth-order switched capacitor band pass filters, the bandwidths of which

correspond to the low and high group frequencies. The filter output is followed by a single order

switched capacitor filter section which smoothes the signals Prior to limiting. Limiting is

performed by high-gain comparators which are provided with hysteresis to prevent detection of

unwanted low-level signals.

Decoder Section :

Digital counting techniques to determine the frequencies of the incoming tones and to verify that

they correspond to standard DTMF frequencies. When the detector recognizes the presence of

two valid tones the “Early Steering” (ESt) output will go to an active state. Any subsequent loss

of signal condition will cause ESt to assume an inactive state.

Steering Circuit :

Before registration of a decoded tone pair, the receiver checks for a valid signal duration

(referred to as character recognition condition). This check is performed by an external RC time

constant driven by ESt. The steering circuit works in reverse to validate the interdigit pause

between signals. Thus, as well as rejecting signals too short to be considered valid, the receiver

will tolerate signal interruptions (dropout) too short to be considered a valid pause. This facility,

together with the capability of selecting the steering time constants externally, allows the

designer to tailor performance to meet a wide variety of system requirements.

Crystal Oscillator :

The internal clock circuit is completed with the addition of an external 3.579545 MHz crystal

Differential Input Configuration :

The input arrangement of the MT8870D/MT8870D-1 provides a differential-input operational

amplifier as well as a bias source (VRef) which is used to bias the inputs at mid-rail. Provision is

made for connection of a feedback resistor to the op-amp output (GS) for adjustment of gain.

The op-amp connected for unity gain and Vref biasing the input at 1/2VDD.

Power-down Mode :

Logic high applied to pin 6 (PWDN) will power down the device to minimize the power

consumption in a standby mode. It stops the oscillator and the functions of the filters.

Inhibit Mode :

Inhibit mode is enabled by a logic high input to the pin 5 (INH). It inhibits the detection of tones.

Applications:

Receiver system for British telecom spec por 1151

Paging systems

Repeater systems/mobile radio

Credit card systems

Remote control

Personal computers

Telephone answering machine

Headset of Nokia

Wiring for the nokia 2.5mm 4-pole headset socket of Nokia 1100, 1101, 1110, 1600, 2100, 2300,

2500, 2650, 2652, 3210, 3310, 3330, 3410, 3510, 3510i, 3650, 3660, 5210, 6030, 6060, 6120,

6510, 6600, 7280, 7380 7650, 8210, 8310, 8800, 8850, 8890, 8910, 8910i cell phones (except

some smart phones

Pin Name Direction Description :

 The answer/end button should be connected across the microphone connections. Microphone

impedance should be 1k4. Speaker is 30 Ohm.

Pin Name Direction Description

1 Tip Speaker+ 2 Ring1 Microphone+3 Ring2 Speaker -4 Sleeve Microphone-

RELAY :

A relay is used to isolate one electrical circuit from another. It allows a low current control

circuit to make or break an electrically isolated high current circuit path. The basic relay consists

of a coil and a set of contacts. The most common relay coil is a length of magnet wire wrapped

around a metal core. When voltage is applied to the coil, current passes through the wire and

creates a magnetic field. This magnetic field pulls the contacts together and holds them there

until the current flow in the coil has stopped. The diagram below shows the parts of a simple

relay.

Figure: Relay

Operation:

When a current flows through the coil, the resulting magnetic field attracts an armature that is

mechanically linked to a moving contact. The movement either makes or breaks a connection

with a fixed contact. When the current is switched off, the armature is usually returned by a

spring to its resting position shown in figure 6.6(b). Latching relays exist that require operation

of a second coil to reset the contact position.

By analogy with the functions of the original electromagnetic device, a solid-state relay operates

a thyristor or other solid-state switching device with a transformer or light-emitting diode to

trigger it.

Pole and throw :

SPST :

SPST relay stands for Single Pole Single Throw relay. Current will only flow through the

contacts when the relay coil is energized.

Figure: SPST Relay

SPDT Relay :

SPDT Relay stands for Single Pole Double Throw relay. Current will flow between the movable

contact and one fixed contact when the coil is De-energized and between the movable contact

and the alternate fixed contact when the relay coil is energized. The most commonly used relay

in car audio, the Bosch relay, is a SPDT relay.

Figure: SPDT Relay

DPST Relay :

DPST relay stands for Double Pole Single Throw relay. When the relay coil is energized, two

separate and electrically isolated sets of contacts are pulled down to make contact with their

stationary counterparts. There is no complete circuit path when the relay is De-energized.

Figure: DPST Relay

DPDT Relay :

DPDT relay stands for Double Pole Double Throw relay. It operates like the SPDT relay but has

twice as many contacts. There are two completely isolated sets of contacts.

Figure: DPDT Relay

This is a 4 Pole Double Throw relay. It operates like the SPDT relay but it has 4 sets of isolated

contacts.

Figure: 4 Pole Double Throw relay

Types of relay :

1. Latching Relay

2. Reed Relay

3. Mercury Wetted Relay

4. Machine Tool Relay

5. Solid State Relay (SSR)

Latching relay :

Latching relay, dust cover removed, showing pawl and ratchet mechanism. The ratchet operates

a cam, which raises and lowers the moving contact arm, seen edge-on just below it. The moving

and fixed contacts are visible at the left side of the image.

A latching relay has two relaxed states (bi-stable). These are also called "impulse", "keep", or

"stay" relays. When the current is switched off, the relay remains in its last state. This is achieved

with a solenoid operating a ratchet and cam mechanism, or by having two opposing coils with an

over-center spring or permanent magnet to hold the armature and contacts in position while the

coil is relaxed, or with a remanent core. In the ratchet and cam example, the first pulse to the coil

turns the relay on and the second pulse turns it off. In the two coil example, a pulse to one coil

turns the relay on and a pulse to the opposite coil turns the relay off. This type of relay has the

advantage that it consumes power only for an instant, while it is being switched, and it retains its

last setting across a power outage. A remanent core latching relay requires a current pulse of

opposite polarity to make it change state.

Figure: Latching relay

Reed relay :

A reed relay has a set of contacts inside a vacuum or inert gas filled glass tube, which protects

the contacts against atmospheric corrosion. The contacts are closed by a magnetic field generated

when current passes through a coil around the glass tube. Reed relays are capable of faster

switching speeds than larger types of relays, but have low switch current and voltage ratings.

Mercury-wetted relay:

A mercury-wetted reed relay is a form of reed relay in which the contacts are wetted with

mercury. Such relays are used to switch low-voltage signals (one volt or less) because of their

low contact resistance, or for high-speed counting and timing applications where the mercury

eliminates contact bounce. Mercury wetted relays are position-sensitive and must be mounted

vertically to work properly. Because of the toxicity and expense of liquid mercury, these relays

are rarely specified for new equipment. See also mercury switch.

Machine tool relay :

A machine tool relay is a type standardized for industrial control of machine tools, transfer

machines, and other sequential control. They are characterized by a large number of contacts

(sometimes extendable in the field) which are easily converted from normally-open to normally-

closed status, easily replaceable coils, and a form factor that allows compactly installing many

relays in a control panel. Although such relays once were the backbone of automation in such

industries as automobile assembly, the programmable logic controller (PLC) mostly displaced

the machine tool relay from sequential control applications.

Solid-state relay :

A solid state relay (SSR) is a solid state electronic component that provides a similar function to an electromechanical relay but does not have any moving components, increasing long-term reliability. With early SSR's, the tradeoff came from the fact that every transistor has a small voltage drop across it. This voltage drop limited the amount of current a given SSR could handle. As transistors improved, higher current SSR's, able to handle 100 to 1,200 Amperes, have become commercially available. Compared to electromagnetic relays, they may be falsely triggered by transients.

Figure: Solid relay, which has no moving parts

Specification :

Number and type of contacts – normally open, normally closed, (double-throw)

Contact sequence – "Make before Break" or "Break before Make". For example, the old

style telephone exchanges required Make-before-break so that the connection didn't get

dropped while dialing the number.

Rating of contacts – small relays switch a few amperes, large contactors are rated for up

to 3000 amperes, alternating or direct current

Voltage rating of contacts – typical control relays rated 300 VAC or 600 VAC,

automotive types to 50 VDC, special high-voltage relays to about 15 000 V

Coil voltage – machine-tool relays usually 24 VAC, 120 or 250 VAC, relays for

switchgear may have 125 V or 250 VDC coils, "sensitive" relays operate on a few milli-

amperes

Applications :

Relays are used:

To control a high-voltage circuit with a low-voltage signal, as in some types of modems,

To control a high-current circuit with a low-current signal, as in the starter solenoid of an

automobile,

To detect and isolate faults on transmission and distribution lines by opening and closing

circuit breakers (protection relays),

To isolate the controlling circuit from the controlled circuit when the two are at different

potentials, for example when controlling a mains-powered device from a low-voltage

switch. The latter is often applied to control office lighting as the low voltage wires are

easily installed in partitions, which may be often moved as needs change. They may also

be controlled by room occupancy detectors in an effort to conserve energy,

To perform logic functions. For example, the boolean AND function is realized by

connecting relay contacts in series, the OR function by connecting contacts in parallel.

Due to the failure modes of a relay compared with a semiconductor, they are widely used

in safety critical logic, such as the control panels of radioactive waste handling

machinery.

As oscillators, also called vibrators. The coil is wired in series with the normally closed

contacts. When a current is passed through the relay coil, the relay operates and opens the

contacts that carry the supply current. This stops the current and causes the contacts to

close again. The cycle repeats continuously, causing the relay to open and close rapidly.

Vibrators are used to generate pulsed current.

To generate sound. A vibrator, described above, creates a buzzing sound because of the

rapid oscillation of the armature. This is the basis of the electric bell, which consists of a

vibrator with a hammer attached to the armature so it can repeatedly strike a bell.

To perform time delay functions. Relays can be used to act as an mechanical time delay

device by controlling the release time by using the effect of residual magnetism by means

of a inserting copper disk between the armature and moving blade assembly.

SCHEMATIC EXPLANANTION

In this project we are using 8051microcontroller which is 40-pin controller, Power supply,DTMF

,relay,fan,bulb.

In this project we are interfacing different devices to microcontroller (AT89S52).AT89S52 is the

40 pin DIP (Dual In-Line Package) in this controller we have 32 I/O pins. To these Pins we can

connect to any devices and can be used as input /output devices. In order to make the IC work we

need to supply some voltage i.e., 5V supply is given to microcontroller i.e., 40 pin and GND is

connected to 20 pin to microcontroller.

Internal Clock frequency of microcontroller is 12MHz, in order to trigger the controller we have

to give the external clock frequency or external clock pulses i.e., 11.0592 MHz approximately it

is generated by the quad crystal from pins 18 & 19 in controller (XLAT1 & XLAT2).For

resetting the controller we have to connect a capacitor, a resister and a switch to 9 pin in

controller.

Relay is used for automatic switching purpose or On/Off the motor. The relay is connected to

port 2.6; here relay is 5-pin in that 2-pins is for GND and Vcc,1 pin is fan and remaining two

pins are used for normally open and normally closed. Motor is connected to normally open pin to

the relay. Second relay is connected to bulb.

CODING

#include <reg51.h>

#include <string.h>

#include "lcd.h"

sbit a1=P0^0;

sbit a2=P0^1;

sbit a3=P0^2;

sbit a4=P0^3;

void main(void)

{

unsigned char a=0,b=0,c=0,d=0;

a1=0;

a2=0;

LCD_init();

while(1)

{

a=P2;

if((a&0xff)==0xe1)

{

a++;

if(a==4)

a=0;

}

if((a&0xff)==0xe2 )

{

b++;

if(b==4)

b=0;

}

if((a&0xff)==0xe3)

{

c++;

if(c==4)

c=0;

}

if((a&0xff)==0xe4)

{

d++;

if(d==4)

d=0;

}

if((a&0xff)==0xe5)

{

}

if((a&0xff)==0xe6)

{

}

if((a&0xff)==0xe7)

{

}

if((a&0xff)==0xe8)

{

}

if((a&0xff)==0xe9 )

{

}

if((a&0xff)==0xea )

{

if(a==3)

{

a1=1;

LCD_puts("BULB ON ");

}

if(b==3)

{

a1=0;

LCD_puts("BULB OFF");

}

if(c==3)

{

a2=1;

LCD_puts("FAN ON ");

}

if(d==3)

{

a2=0;

LCD_puts("FAN OFF");

}

}

}

}

LCD :

#include <reg51.h>

#include<stdio.h>

sbit LCD_en=P1^2;

sbit LCD_rs=P1^3;

#define LCD_DELAY 1535 /* Delay for 1 ms */

#define LCD_clear() LCD_command(0x1) /* Clear display LCD */

#define LCD_origin() LCD_command(0x2) /* Set to origin LCD */

#define LCD_row1() LCD_command(0x80) /* Begin at Line 1 */

#define LCD_row2() LCD_command(0xC0) /* Begin at Line 2 */

#define SHIFT_left() LCD_command(0x18) /* Shift Left */

#define SHIFT_right() LCD_command(0x1c) /* Shift Right */

/***************************************************

* Prototype(s) *

***************************************************/

void LCD_delay(unsigned char ms);

void LCD_enable();

void LCD_command(unsigned char command);

void LCD_putc(unsigned char ascii);

void LCD_puts(unsigned char *lcd_string);

void LCD_init();

/***************************************************

* Sources *

***************************************************/

void LCD_delay(unsigned char ms)

{

unsigned char n;

unsigned int i;

for (n=0; n<ms; n++)

{

for (i=0; i<LCD_DELAY; i++); /* For 1 ms */

}

}

void LCD_enable()

{

LCD_en = 0; /* Clear bit P2.4 */

LCD_delay(1);

LCD_en = 1; /* Set bit P2.4 */

}

void LCD_command(unsigned char command)

{

LCD_rs = 0; /* Clear bit P2.5 */

P1 = (P1 & 0x0F)|((command) & 0xF0);

LCD_enable();

P1 = (P1 & 0x0F)|((command<<4) & 0xF0);

LCD_enable();

LCD_delay(1);

}

void LCD_putc(unsigned char ascii)

{

LCD_rs = 1; /* Set bit P2.5 */

P1 = (P1 & 0x0F)|((ascii) & 0xF0);

LCD_enable();

P1 = (P1 & 0x0F)|( (ascii << 4) & 0xF0);

LCD_enable();

LCD_delay(1);

}

void LCD_puts(unsigned char *lcd_string)

{

while (*lcd_string)

{

LCD_putc(*lcd_string++);

}

}

void LCD_init()

{

LCD_en = 1; /* Set bit P2.4 */

LCD_rs = 0; /* Clear bit P2.5 */

LCD_command(0x33);

LCD_command(0x32);

LCD_command(0x28);

LCD_command(0x0C);

LCD_command(0x06);

LCD_command(0x01); /* Clear */

LCD_delay(256);

}

void LCD_xy(unsigned char column, unsigned char row)

{

unsigned char Temp;

switch(row-1)

{

case 0: Temp = 0x00+column-1;

break;

case 1: Temp= 0x40+column-1;

break;

case 2: Temp= 0x14+column-1;

break;

case 3: Temp = 0x54+column-1;

break;

default: Temp = 0x00+column-1;

}

LCD_command(Temp|0x80);

}

void PRINT_long( int Data)

{

int Temp = Data;

char Arr[9],i=0;

if(Data=='\0'||Data==0)

{

LCD_putc('0');

return;

}

do

{

Arr[i++]=Data%10;

Temp/=10;

Data=Temp;

}while(Temp>0);

while(i--)

LCD_putc(Arr[i]+48);

}

CONCLUSION

The project “advance security using mobile phone” is used for the controlling the devices

which are operated by the mobile phone. To prove this practically we use a mobile phone as the

transmitter part. In the receiver part we have DTMF receiver, relays which are connected to the

devices.

APPLICATIONS :

They are used at the security purpose places like shopping malls, offices, software companies,

house, apartments, star hotels, film theaters.

BIBLIOGRAPHY :

The 8051 Micro controller and Embedded Systems Muhammad Ali Mazidi Janice Gillispie Mazidi

The 8051 Micro controller Architecture, Programming & Applications

Kenneth J. Ayala

Fundamentals of Micro processors and Micro computers B. Ram

Micro processor Architecture, Programming & Applications Ramesh S. Gaonkar

Electronic Components D.V.Prasad

References on the Web:

www.national.comwww.atmel.com

www.microsoftsearch.comwww.geocities.comwww.google.com