embedded system ucontrollr

8/9/2019 Embedded System Ucontrollr

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CHAPTER 1

1.1 COMPANY PROFILE

1.1.1 ORIGIN

Emtech Foundation is founded by highly skilled and enthusiastic young embedded engineers. The

founding members of the company are having a rich industrial experience in embedded system

designing. The company is located in New Delhi (India).

1.1.2 CEO

Mr. Naveen Kumar is the Founder Chairman and CEO of the company. He has been the Project

and Chief Training Manager in the relevant industry. He has organized the embedded workshopsin northern and western India, with a high exposure in the robotics design and system analysis .

1.1.3 WORK

Emtech Foundation has highly skilled team for customized product design including hardware and

software, Multilayer PCB Design, prototyping and robot programming. Emtech Foundation is also

having Excellent Training Center on the relevant technologies.

1.1.4 MISSION

Our mission to setup the best Robotic Design Center in India. The Company has a mission to ready

the innate engineer from basic level to a skilled one by providing them training on 8 bit

microcontroller/microprocessor to 64-bit for embedded and robotic design. The Mission summery

is to build the nation with real robotic engineers by providing them right training and

infrastructure.

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1.1.5 VISION

The time is ruled by NANOTECHNOLOGY AND THE ROBOTICS. The things are getting

automated day by day and we are getting more dependent on machine and auto life.

The coming time will demand for highly skilled robotic engineers and embedded technologists. All

the technologies, whether it is telecommunication, medical engineering, integrated securities or

space technologies all are demanding embedded engineers with a high level of basics.

Emtech Foundation is having a vision over this. We are preparing the real engineers by providing

them excellent infrastructure and highly processed environment to pack them with an extra in the

mean time. The seminars and workshops by edge industry representatives have been proved

unbeatably productive.

Our focus is on engineering students from 3rd semester to the final year. Because the embedded

technologies can give best result and a better direction while one is a student. This focus can

change the view of young engineers over embedded technologies. We have a vision of specified

and easy going theory and practical sessions. Emtech Foundation is having highly equipped labs

and skilled guides.

We, Engineering the Engineers, Emtech Foundationigniting minds..

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1.2 INTRODUCTION

Microcontrollers 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 performs 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. For example inside every mouse there is microcontroller to perform the

task of finding the mouse position and sending it to PC.

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, Motorola, 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, Motorola 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 isto integrate more & more function on the CPU chip & let the designer decide which feature he/she

wants to us.

CHAPTER 2

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LITERATURE REVIEW

2.1 What IS EMBEDDED SYSTEM?

2.1.1DEFINITION:

An embedded system is a combination of Hardware and Software design to meet a specific

need with performance in a given time frame.

An embedded controller is a device that is embedded into some device for some purpose other

than to provide general purpose computing.

FIG 2.1:- EMBEDDED SYSTEM

2.2FEATURES OF AN EMBEDDED SYSTEM

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2.2.1 REAL TIME AND REACTIVE OPERATIONS

Real time system operation means that the correctness of a computation depends, in part, on the

time at which it is delivered. In many cases the system design must take into account worst case

performance. Predicting the worst case may be difficult on complicated architectures, leading to

overly pessimistic estimates erring on the side of caution. The Signal Processing and Mission

Critical example systems have a significant requirement for real time operation in order to meet

external I/O and control stability requirements. Reactive computation means that the software

executes in response to external events. These events may be periodic, in which case scheduling of

events to guarantee performance may be possible.

On the other hand, many events may be a periodic, in which case the maximum event arrival rate

must be estimated in order to accommodate worst case situations. Most embedded systems have a

significant reactive component.

2.2.2 SMALL AND LOW WEIGHT SIZE

Many embedded computers are physically located within some larger artifact. Therefore, their

form factor may be dictated by aesthetics, form factors existing in pre-electronic versions, or

having to fit into interstices among mechanical components. In transportation and portable

systems, weight may be critical for fuel economy or human endurance. Among the examples, the

Mission Critical system has much more stringent size and weight requirements than the others

because of its use in a flight vehicle, although all examples have restrictions of this type.

SAFE AND RELIABLE

Some systems have obvious risks associated with failure. In mission-critical applications such as

aircraft flight control, severe personal injury or equipment damage could result from a failure of

the embedded computer. Traditionally, such systems have employed multiply-redundant computers

or distributed consensus protocols in order to ensure continued operation after an equipment

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failure. However, many embedded systems that could cause personal or property damage cannot

tolerate the added cost of redundancy in hardware or processing capacity needed for traditional

fault tolerance techniques. This vulnerability is often resolved at the system level as discussed

later.

HARSH ENVIRONMENT

Many embedded systems do not operate in a controlled environment. Excessive heat is often a

problem, especially in applications involving combustion ( e.g., many transportation applications).

Additional problems can be caused for embedded computing by a need for protection from

vibration, shock, lightning, power supply fluctuations, water, corrosion, fire, and general physicalabuse. For example, in the Mission Critical example application the computer must function for a

guaranteed, but brief, period of time even under non-survivable fire conditions.

COST SENSITIVITY

Even though embedded computers have stringent requirements, cost is almost always an issue(even increasingly for military systems). Although designers of systems large and small may talk

about the importance of cost with equal urgency, their sensitivity to cost changes can vary

dramatically. A reason for this may be that the effect of computer costs on profitability is more a

function of the proportion of cost changes compared to the total system cost, rather than compared

to the digital electronics cost alone. For example, in the Signal Processing system cost sensitivity

can be estimated at approximately $1000 (i.e. , a designer can make decisions at the $1000 levelwithout undue management scrutiny).

However, with in the Small system decisions increasing costs by even a few cents attract

management attention due to the huge multiplier of production quantity combined with the higher

percentage of total system cost it represents.

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2.2 APPLICATIONS :-

2.3.1 TELECOM

Modems and routers

2.3.2 AUTOMOTIVE APPLICATIONS

Braking system

Traction control

Airbag release system

2.3.3 DOMESTIC APPLIANCE

Dishwashers, televisions, Washing machines, Microwave ovens, Video recorders

2.3.4 ROBOTICS

Fire fighting robots, automatic floor cleaner, robotic arm

2.3.5 AEROSPACE APPLICATIONS

Flight control system, engine controller, autopilots

2.3.6 MEDICAL APPLICATION

ECG monitors, MRI scanners

2.3.7 DEFENSE SYSTEM

Radar system, radio system, missile guidance system

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2.3.8 OFFICE AUTOMATION

Laser printers, fax machines, pagers, cash registers, credit/debit card reader

And Many More.2.4 WHAT IS A MICROCONTROLLER?

2.4.1 INTRODUCTION:

A microcontroller is a computer-on-a-chip used to control electronic devices. It is a type of

microprocessor emphasizing self-sufficiency and cost-effectiveness, in contrast to a general-

purpose microprocessor, the kind used in a PC. A typical microcontroller contains all the memory

and I/O interfaces needed, whereas a general purpose microprocessor requires additional chips to

provide these necessary functions.

An embedded controller is a device that is embedded into some device for some purpose

other than to provide general purpose computing.

Figure shows the block diagram of a typical microcontroller, which is a true computer on a chip.

The design incorporates all of the features found in micro-processor CPU: ALU, PC, SP, and

registers. It also added the other features needed to make a complete computer: ROM, RAM,

parallel I/O, serial I/O, counters, and clock circuit.

FIG 2.2:- MICROCONTROLLER AS A COMPUTER CHIP

2.5 WHAT IS MICROPROCESSOR?

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RAM ROM

I/OPort

TimerSerialCOMPort

CPU

A single chip


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2.5.1 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. A

microprocessor fetches each program instruction in sequence, decodes the instruction, and executes

it. The central processing unit (CPU) is the most well known microprocessor. Microprocessor means chip used for general purpose programming. For example 8085, 8086, 80286, 80386,

80486, Pentium etc.

These up contain no RAM, no ROM and no other I/O ports devices on the chip itself.

2.5.2 BLOCK DIAGRAM

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 2.3:- BLOCK DIAGRAM OF A MICROPROCESSOR

MEMORY:

Memory section is mixture of RAM and ROM. the first purpose is to store the binary codes for the

sequences of instructions you want the computer to carry out. Second purpose of the memory is to

store the binary coded data with which the computer is going to be working.

INPUT/OUTPUT PORTS :

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CPUGeneral-PurposeMicro-

processor

RAM ROM I/O

Port

TimerSerialCOM

Port

Data Bus


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The actual physical devices used to interface the computer buses to external systems are often

called ports. An input port allows data from keyboard or some other source to be read into the

computer under control of the CPU .An output port is used to send data from the computer to some

peripheral devices.

CENTRAL PROCESSING UNIT:

CPU controls the operation of the computer. CPU fetches binary-coded instructions from memory,

decodes the instructions into a series of simple action, and carries out these actions in a sequence

of steps.

ADDRESS BUS:

The address bus consists of 6, 20, 24 or 32 parallel signal lines. On these lines the CPU sends outthe address of the memory location that is to be written to or read from.

DATA BUS:

The data bus consists of 8, 6 or parallel signal lines. Indicated by double arrows i.e.; bidirectional

this means CPU can read data in from memory or from a port on these lines.

CONTROL BUS:

The control bus consists of to parallel signal lines. The CPU sends out signals on the control bus to

enable the outputs of addressed memory devices or port devices.

2.6 DIFFERENCE BETWEEN MICRO-PROCESSOR AND MICRO-CONTROLLER:-

Microcontroller and microprocessor stems from the same basic idea yet there exist some

differences. Table1.1 clearly differentiates between microprocessor and microcontroller.

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TABLE 2.1:- MICROPROCESSOR V/S MICROCONTROLLER

S.NO. Feature Microprocessor Microcontroller

1. Memory No on chip Ram/Rom On chip Ram/Rom2. Application General purpose Specific purpose3. Timer No on chip timer Two on chip timer 4. Opcodes Many opcodes for moving

data from external memoryto the C.P.U.

Microcontrollers mayhave one or twoopcodes.

5. Example 8086,80186 8051

2.7 TYPES OF MICROCONTROLLER:

Every application demands a microcontroller that offers the right amount of functionality at the

minimum cost. Applications vary from controlling an appliance to controlling an automobile. No

single microcontroller design can economically meet these demands, so semiconductor

manufacturers offer an array of microcontrollers designed to handle data in 4-, 8-, 16- and 32-bit

words.

2.7.1 FOUR-BIT MICROCONTROLLER:

In terms of sheer volume, 4-bit microcontroller may be used more than any other type. For a

commodity microcontroller, cost depends as much on the volume of the package and the number

of pins as on the amount of silicon inside. Pin count, in turn, depends on the number of data bits

commonly handled by the microcontroller, and its I/O capability. Using 4-bits reduces package

cost and pin count to a minimum. Employed in applications ranging from alphanumeric LED/LCD

display drivers to portable battery chargers, these are the least expensive smart chips available.

An example of contemporary 4-bit microcontroller is the Renasas M34501, in a 20-pin DIP.

RAM ROM Counters I/O Pins Other Features

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256 4k 2 14 A/D

2.7.2 EIGHT-BIT MICROCONTROLLER:

Eight-bit microcontrollers are perhaps the most popular microcontrollers in use today,

Judging from the number of semiconductor companies making them. Eight-bit have proven to be a

very useful word size for everyday controller tasks. Capable of 256 decimal values, or quarter-

percent resolution, the 1-byte data word is adequate for many control and monitoring applications.

Serial ASCII code is also byte size, making 8-bits the natural choice for data communication

applications. In addition, most low-cost RAM and ROM memories store 1-byte per memory

location for easy interfacing to an 8-bit microcontroller.One indication of the popularity of 8-bit microcontrollers is the fact that some 44 manufacturers

produce over 600 models based on the 8051 architecture alone. Other popular microcontrollers,

such as those designed by Microchip, Motorola, and Zilog, add hundreds of additional choices to

the 8-bit menu. Here is what the 8051 offers when mounted in a 40-pin DIP:

RAM ROM Counters I/O Pins Other Features128 bytes 4k 2 32 UART

2.7.3 SIXTEEN-BIT MICROCONTROLLERS:

Sixteen-bit microcontrollers offer much of the generality of 8-bit models, but with greatly

increased memory size and speed. Sixteen-bit microcontrollers are much better suited for

programming in high-level languages, such as C.

Application of 16-bit microcontrollers are calculation and data intensive and include disk drives,

modems, printers, scanners, pattern recognition, and automotive and servomotor control. A typical

16-bit microcontroller, the Motorola 68HC16Z3, has these attributes when mounted in a 144-leadLQFP package:

RAM ROM Counters I/O Pins Other Features4k 8k 2 24 A/D,UART

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2.7.4 THIRTY-TWO-BIT MICROCONTROLLERS:

Thirty-two-bit microcontrollers are currently evolving away from general purpose applications to

targeted markets such as PDAs, GPS, automotive control, communication networks, robotics,

entertainment/game boxes, digital cameras, cell phones, and similar high-end uses. As an example,

the Sharp LH79520 housed in a 176-pin LQFP package offers following features, most of which

could be used to implement a notebook computer: 32k RAM, color LCD controller, three UARTs,

synchronous serial, two PWMs, 64 I/O pins, four counters, WDT , real-time-clock, PLL, and direct

memory access (DMA). Clearly the development of 32-bit microcontrollers is driven by large,

well-defined markets.

FIG 2.4:- COMPARISON OF DIFFERENT MICROCONTROLLERS

2.8 8051 MICROCONTROLLER

2.8.1 A BRIEF HISTORY:

In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051.

This microcontroller had 128 bytes of RAM, 4k bytes of on-chip ROM, two timers, one serial

port, and four ports9 each 8-bits wide) all on a single chip. At that time I was referred to as a

system on a chip.

The 8051 is an 8-bit processor, meaning that the CPU can work only 8 bits of data at a time.

Data larger than 8 bits has to be broken into 8-bit pieces to be processed by the CPU.

Intel refers to it as MCS-51 now.

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2.8.2 STANDARD FEATURES:

8 bit data path and ALU.

4k*8 ROM-program memory.

128*8 RAM-data memory.

Multiple 16-bit Timer/Counter.

On chip clock oscillator.

2.8.3 Family members of 8051:

Family members of 8051 microcontroller are 8031, 8032 and 8052. Table 1.2 shows the features

of different family members 8051.

TABLE 2.2: FAMILY MEMBERS OF 8051

Feature 8051 8031 8052 8032

ROM 4K 0K 8K 0K

RAM(bytes) 128 128 256 256

Timers 2 2 3 3

I/O Pins 32 32 32 32

Serial Port 1 1 1 1

Interruptsources

6 6 7 7

2.8.4 VERSION OF 8051 MICROCONTROLLER:

Intel allowed other manufacturers to make and market any version of 8051 depending upon the

speed and on chip ROM. All versions are code compatible.

AT89C51from ATMEL CORPORATION:

On chip ROM flash memory, erase cycles in seconds, furnish fast development.

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DS5000 from Dallas Semiconductor:

On chip ROM in form of NV-RAM form. NV-RAM has the ability to change the ROM

contents one byte at a time.

OTP( one time programmable) version of 8051:

For mass production, low cost

8051 family from Philips:

One of the largest selections of 8051 microcontrollers, various features like ADC, DAC,

extended I/O, both OTP and flash.

There are more than 50 companies like ST, TI, SIEMENS, and WINBOND

etc. making microcontroller chips based on Intel 8051 architecture world

wide.

2.9 BLOCK DIAGRAM OF 8051

FIG 2.5: BLOCK DIAGRAM OF 8051

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2.9.1 INTERRUPT CONTROL

The interrupt control basically handles the interrupts whether they should be handled or.

For the same purpose two registers of 8-bits are present i.e. IP and IE i.e. interrupt priority

and interrupt enable.

2.9.2 ON CHIP FLASH

Flash memory is present on the chip.

2.9.3 ON CHIP RAM

RAM is also present on the chip.

2.9.4 TIMER

Timer control registers of 8 bits are also present on the chip. The counter input is given to

the timers.

2.9.5 SERIAL PORTS

The serial ports are also present on chip which allows the microcontroller to communicate

serially.

2.9.6 I/O PORTS

The I/O ports basically provides the input and output ports. These are present on the chip of

microcontroller itself. They are of 8 bits. Basically there are 4 ports i.e. port 0, port 1, port

2 and port 3. PORT 0 provides both data and addresses along with I/O pins. PORT 1

provides only I/O pins. PORT 2 provides I/O pins and the remaining addresses. PORT 3

provides I/O pins and WR, RD, T0, T1, INT0, INT1, RXD, TXD.

2.9.7 BUS CONTROL

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The control registers are present i.e. TCON, TMOD, SCON, PCON, IP, IE.

2.9.8 OSCILLATOR

A particular frequency is provided i.e. 11.0592 MHz by a crystal oscillator.

2.10 PIN DIAGRAM OF 8051:

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FIG 2.6:- PIN DIAGRAM OF 80512.10.1 PIN DESCRIPTION:

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8051 is a 40 pin IC packed in DIP (Dual line packaging). This means that the pin performs the dual

functions. Basically 8051 is a 40 pin IC but it performs 64 functions. This is due to the reason that

24 pins are multiplexed pins. So these pins perform dual functions and make it a total of 64

functions.

PORT 0-PINS(32-39)

Input/output pins.

Required external pull-up resistors of 10K ohm.

Used both as I/O port and higher address byte.

FIG 2.7:- PORT 0 WITH PULL-UP RESISTOR

PORT 1-PINS (1-8):

Input /output pins. Contains internal pull-ups.

PORT 3-PINS (10-17):

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Input/output pins.

Contains internal pull-ups.

Alternate functions to provide signals such as interrupts.

PINS : DESCRIPTIONRXD (P3.0) : Serial input portTXD (P3.1) : Serial output portINT0 (P3.2) : External interruptINT1 (P3.3) : External interruptT0 (P3.4) : Timer 0 external inputT1 (P3.5) : Timer 1 external inputWR (P3.6) : External data memory writes strobeRD (P3.7) : External data memory read strobe

PORT 2-PINS (21-28):

Input/output port.

Contains internal pull-ups.

Used both as I/O port and higher address byte.

PSEN-(PIN 29): PROGRAM STORE ENABLE

Active low input Used while accessing external memory.

Connected to OE pin of external ROM.

ALE-(PIN 30): ADDRESS LATCH ENABLE

Active high.

Used for de-multiplexing the address and data by connecting G pin of 74LS373.

EA-(PIN 31): EXTERNAL ACCESS

Active low input.

To access external ROM it must be grounded.

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XTAL1 AND XTAL2-(PIN 18 AND PIN 19):

Provides electric field to quartz crystal oscillator for oscillations.

RESET-(PIN 9):

Active high input.

Terminate all activities of microcontroller.

Sets PC to 0000h

Requires minimum 2 machine cycles.

TABLE 2.3- RESET VALUE OF SOME 8051

REGISTER RESET VALUE

PC 0000 hACC 0000 hB 0000 hPSW 0000 hSP 0007 hDPTR 0000 h

VCC-(PIN 40): Provides supply voltage to the chip. The voltage source is+5v.

GND-(PIN 20):

This pin is grounded

CRYSTAL CONNECTION:

The 8051 has an on-chip oscillator but requires an external clock to run it. Mostoften a quartz crystal is connected to inputs XTAL1 (pin 19) and XTAL2 (pin18). The

quartz crystal connected to XTAL1 and XTAL2 also needs two capacitors of 30pf value.

One side of each capacitor is connected to ground as shown in figure 1.8.

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A functioning computer must have memory for program code bytes, commonly in ROM, and

RAM memory for variable data that can be altered as the program runs. The 8051 has internal

RAM and ROM memory for these functions.

2.11.1 INTERNAL RAM:

The 128-byte internal RAM, which is organized into three distinct areas:

1. Thirty-two bytes from address 00h to 1Fh that makes up 32 working registers organized as four

banks of eight register each. The four banks are numbered 0 to 3and are made up of eight

registers named R0 to R7. Each register can be addressed by name or by its RAM address.

Thus R0 of bank 3 is R0 (if bank 3 is currently selected0 or by its RAM address 18h (whether

bank 3 is selected or not). Bits RS0 and RS1 in the PSW determine which bank of registers iscurrently in use at any time when the program is running. Register bank not selected can be

used as general purpose RAM. Bank 0 is selected on reset.

2. A bit-addressable area of 16 bytes occupies RAM byte addresses 20h to 2Fh, forming a total

of 128 addressable bits.

3. A general purpose RAM area above the bit area, from 30h to 7Fh, addressable as bytes.

2.11.2 STACK AND STACK POINTER:

The Stack refers to an area of internal RAM that is used in conjunction with certain opcodes to

store and retrieve data quickly. The 8-bit Stack Pointer (SP) register is used by the 8051 to hold

an internal RAM address that is called the top of the stack. The address held in SP register is

the location in internal RAM where the last byte of data was stored by a stack operation.

When data is to be placed on the stack, the SP increments before storing data on the stack so

that the stack grows up as data is stored. As data is retrieved from the stack, the byte is read

from the stack, and then the SP decrements to point to the next available byte of stored data.

Operation of the stack and the SP register is shown in figure. The stack is set to 07h when 8051

is reset and can be changed to any internal RAM address by the programmer, using a data

move command.

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FIG 2.9: -STACK OPERATION

2.11.3 INTERNAL ROM:

The 8051 is organized so that data memory and program code memory can be in two entirely

different physical memory entities. Each has the same address ranges. The structure of internal

RAM has been discussed previously. A corresponding block of internal ROM occupies code

address space 0000h to 0FFFh. Following are some features internal ROM:Begins from location 0000h

Each interrupt is assigned a fixed location in it (0000-0023H)

The PC is used to address program code bytes from addresses 0000h to 0FFFh.

FIG 2.10:- INTERNAL ROM

24

SP=0A Address 0A SP=0A

SP=09

SP=08

SP=07

PUSH POP

Address 09

Address 08

Address 07

SP=09

SP=08

SP=07

Internal RAMStoring data on the Stack (Increment then store)

Getting data from the Stack (Get then decrement)

Store Data

Store Data

Store Data

Get Data

Get Data

Get Data

0000

0FFF

B te

INTERNALROM


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2.11.4 MACHINE CYCLE AND STATE:

The smallest interval of time to accomplish any simple instruction, or part of a complex

instruction is called a machine cycle.

The machine cycle is itself made up of six states.

A state is the basic time interval for discrete operations of the microcontroller such as fetching

an opcode byte, decoding an opcode, executing an opcode, or writing a data byte.

Two oscillator pulses define each state. The clock frequency, f, establishes the smallest interval

of time within the microcontroller, called the pulse, p, time.

Program instructions may require one, two, or four machine cycles to be executed, depending

on the type of instruction.

If number of cycles to execute an instruction are known, then execution time of that instructionis given by:

T (instruction) = (C*12)/crystal frequency

FIG 2.11:-ONE COMPLETE MACHINE CYCLE

2.11.5 SPECIAL FUNCTION REGISTER:

The 8051 operations that dont use the 128-byte internal RAM addresses from 00h to 7Fh aredone by a group of specific internal register, each called a Special Function register (SFR),

which may be addressed much like internal RAM, using addresses 80h to FFh.

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State 1 State 2 State 3 State 4 State 5 State 6

One Machine Cycle

P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2


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Some SFRs are also bit addressable, as in the case for bit area of RAM. This feature allows the

programmer to change only what needs to be altered, leaving the remaining bits in the SFR

unchanged.

Special Function Register Map is shown in figure 1.16.

SFR map includes following registers:

CPU Register

- ACC : ACCUMULATOR

- B : B REGISTER

I/O PORT

- P0 : PORT 0 LATCH

- P1 : PORT 1 LATCH

- P2 : PORT 2 LATCH

- P3 : PORT 3 LATCH

TIMERS

- TMOD : TIMER/COUNTER MODE CONTROL

- TCON : TIMER/COUNTER CONTROL

- TH0 : TIMER 0 LOW BYTE

- TL0 : TIMER 0 HIGH BYTE

- TH1 : TIMER 1 LOW BYTE

- TL1 : TIMER 1 HIGH BYTE

SERIAL I/O- SCON : SERIAL PORT CONTROL

- SBUF : SERIAL PORT DATA BUFFER

OTHER

- PCON : POWER CONTROL

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2.11.6 A AND B REGISTER:

The 8051 contains 34 general-purpose or working registers. Two of these, register A and B, hold

results of many instructions, particularly math and logical operations, of the 8051 central

processing unit (CPU).

A (ACCMULATOR)

8-bit register and is used as working register for the arithmetic and logical instructions.

Also used for all data transfer between the 8051 and any external memory Can be used as working register.

Necessary for some instructions.

B REGISTER:

8-bit register and can be used as general purpose register.

Necessary for the instructions MUL and DIV

2.11.7 FLAGS AND THE PROGRAM STATUS WORD (PSW):

Flags are 1-bit registers provided to store the results of certain program instructions. Other

instructions can test the condition of the flags and make decisions based on the flag states. In

order that the flags may be conveniently addressed, they are grouped inside the program status

word (PSW) and the power control (PCON) registers.

The 8051 has four math flags that respond automatically to the outcomes of math operations

and three general-purpose user flags that can be set to1 or cleared to 0 by the programmer as

desired. The math flag include Carry (C), Auxiliary Carry (AC), Overflow (OV), and parity

(P). User flags are named F0, GF0, and GF1; they are general-purpose flags that may be used

by the programmer to record some event in the program.

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The program status word is shown in figure. The PSW contains the math flags, user program

flag F0, and the register select bits that identify which of the four general-purpose register

banks is currently in use by the program.

TABLE 2.4: PROGRAM STATUS WORD

7 6 5 4 3 2 1 0CY AC F0 RS1 RS0 OV -------- P

BIT SYMBOL

FUNCTION

7 CY Carry flag; used in arithmetic, jump, rotate and Booleaninstruction

6 AC Auxiliary Carry flag; used for BCD arithmetic

5 F0 User flag 0

4 RS1 Register bank select bit 1

3 RS0 Register bank select bit 0

RS1 RS00 0 Select register bank 00 1 Select register bank 11 0 Select register bank 21 1 Select register bank 3

2 OV Overflow flag; used in arithmetic instructions

1 ----- Reserved for future use

0 P Parity flag; shows parity of register A: 1= Odd parity

3.9 COUNTERS AND TIMERS

Many microcontroller applications require the counting of external events, such as the frequency of

a pulse train, or the generation of precise internal time delays between computer actions. Both of

these tasks can be accomplished using software techniques, but software loops for counting or

28

Bit addressable as PSW.0 to PSW.1


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timing keep the processor occupied so that other, perhaps more important, functions are not done.

To relieve the processor of this burden, two 16-bit up counters, named T0 and T1, are provided for

the general use of the programmer. Each counter may be programmed to count internal clock

pulses, acting as a timer, or programmed to count external pulses as a counter.

2.12 TIMER

Both timer 0 and timer 1 are 16 bits wide. Since the 8051 has an 8-bit architecture, each 16-bit

timer is accessed as two separate registers of low byte and high byte.

2.12.1 TIMER 0 REGISTER:

The 16-bit register of timer 0 is accessed as low and high byte. The low byte register is called TL0

(timer 0 low byte) and the high byte register is referred to as TH0 (timer 0 high byte). Theseregisters can be accessed like any other register, such as A, B, R0, R1, R2 etc. For example, the

instruction MOV TL0, #4Fh moves the value 4Fh into TL0, the low byte of timer 0. These

registers can also be read like any other register. For example, MOV R5, TH0 saves TH0 (high

byte of timer 0) in R5.

2.12.2 TIMER 1 REGISTER:

Timer 1 is also 16 bits, and its 16-bit register is split into two bytes, referred to as TL1 (timer 1 low

byte) and TH1 (timer 1 high byte). These registers are accessible in the same way as the registers

of timer0.

29

TH0 TL0

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

FIG 2.11: TIMER 0 REGISTER

TH1 TL1

FIG 2.12: TIMER 1 REGISTER


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2.12.3 TIMER ACTION :

All counter action is controlled by bit states in the timer mode control register (TMOD), the

timer/counter control register (TCON), and certain program instructions.

THE TIMER CONTROL (TCON) SPECIAL FUNCTION REGISTER:

TABLE 2.5: TCON REGISTER 7 6 5 4 3 2 1 0

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

BIT SYMBOL FUNCTION7 TF1 Timer 1 Overflow flag. Set when timer rolls from all 1s to 0.

Cleared when processor vectors to execute interrupt serviceroutine located at program address 001Bh.

6 TR1 Timer 1 run control bit. Set to 1 by program to enable timer to count; cleared to 0 by program to halt timer. Does not resettimer.

5 TF0 Timer 0 Overflow flag. Set when timer rolls from all 1s to 0.Cleared when processor vectors to execute interrupt serviceroutine located at program address 000Bh.

4 TR0 Timer 0 run control bit. Set to 1 by program to enable timer to count; cleared to 0 by program to halt timer. Does not resettimer

3 IE1 External interrupt 1 Edge flag. Set to 1 when a high-to-lowedge signal is received on port 3 pin 3.3. Cleared when

processor vectors to interrupt service routine located at program address 0013h. Not related to timer operations.

2 IT1 External interrupt 1 signal type control bit. Set to 1 by program to enable external interrupt 1 to be triggered by afalling edge signal. Set to 0 by program to enable a low-levelsignal on external interrupt 1 to generate an interrupt.

1 IE0 External interrupt 0 Edge flag. Set to 1 when a high-to-lowedge signal is received on port 3 pin 3.2. Cleared when

processor vectors to interrupt service routine located at program address 0003h. Not related to timer operations.

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TABLE 2.7: TIMER MODES

M1 M0 MODE OPERATING MODE

0 0 0 13-bit timer mode8-bit timer/counter THx with TLxas 5-bit prescalar

0 1 1 16-bit timer mode16-bit timer/counter THx and TLxare cascaded; there is no prescalar

1 0 2 8-bit auto reload8-bit auto reload timer/counter;THx holds a value which is to bereloaded into TLx each time itoverflows.

1 1 3 Split timer mode

2.13.1 TIMER MODE 0

Setting timer X mode bits to 00b in the TMOD register results in using the THX register as an 8-

bit counter and TLX as a 5-bit counter; the pulse input is divided by 32d in TL so that TH counts

the original oscillator frequency reduced by a total 384d. As an example, the 6 megahertz oscillator

frequency would result in a final frequency to TH of 15625 hertz. The timer flag is set whenever

THX goes from FFh to00h, or in .0164 seconds for a 6 megahertz crystal if THX starts at 00h.

2.13.2 TIMER MODE 1

The following are the characteristics and operation of mode 1:

1. It is a 16-bit timer; therefore, it allows values of 0000h to FFFFh to be loaded into thetimers registers TL and TH.

2. After TL and TH are loaded with a 16-bit initial value, the timer must be started. This is

done by SETB TR0 for timer 0 and SETB TR1 for timer 1.

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TLX 5 Bits THX 8 Bits TFX InterruptFIG 2.13:- TIMER MODE 0 13-BIT TIMER/COUNTER

PULSEINPUT


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3. After the timer is started, it starts to count up. It counts up until it reaches its limit of

FFFFh. When it rolls over from FFFFh to 0000, it sets high a flag bit called TF (timer

flag). This timer flag can be monitored. When this timer flag is raised, one option would

be to stop the timer with the instructions CLR TR0 or CLR TR1, for timer 0 and timer

1, respectively. Again, it must be noted that each timer has its own timer flag; TF0 for

timer 0, and TF1 for timer 1.

4. After the timer reaches its limit and rolls over, in order to repeat the process the register

TH and TL must be reloaded with the original value, and TF must be reset to 0.

FIG 2.14:- TIMER MODE 1 OPERATION

2.13.3 TIMER MODE 2

The following are the characteristics and operation of mode 2:

1. It is an 8-bit timer; therefore, it allows only values of 00 to FFh to be loaded into the timers

register TH.

2. After TH is loaded with the 8-bit value, the 8051 gives a copy of it to TL. Then the timer

must be started. This sis done by the instruction SETB TR0 for timer 0and SETB TR1

for timer 1.this sis just like mode 1.

3. After the timer is started, it starts to count up by incrementing the TL register. It

counts up until it reaches its limit of FFh. When it rolls over from FFh to 00, it sets high the

TF (timer flag). If we are using timer 0, TF0 goes high; if we are using timer 1, TF1 is raised.

33

THH TL

TFH

TF goes highWhen FFFF

OverflowFlag0

/12d

TR

XTALOscillator

C/T=0


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FIG 2.15:- TIMER MODE 2 OPERATION

4. When the TL register rolls from FFh to 0 and TF is set to 1, TL is reloaded automatically

with the original value kept by the TH register. To repeat the process, we must simply clear

TF and let it go without any need by the programmer to reload the original value. This makes

mode 2 an auto reload, in contrast with mode 1 in which the programmer has to reload TH

and TL. It must be emphasized that mode 2 is an 8-bit timer. However, it has an auto-

reloading capability. In auto-reload, TH is loaded with the initial count and a copy of it is

given to TL. This reloading leaves TH unchanged, still holding a copy of original value.

2.13.4 TIMER MODE 3

1. Timer 0 and 1 may be programmed to be in mode 0, 1, or 2independently of asimilar mode

for the other timer. This is not true for mode 3; the timers dont operate independently if

mode 3 is chosen for timer 0. Placing timer 1 in mode 3cause tit to stop counting; the

control bit TR1 and the timer1 flag TF1 are then used by timer 0.

2. Timer 0 in mode 3 becomes two completely separate 8-bit counters. TL0 is controlled by

the gate and sets timer flag TF0whenever it overflows from FFh to 00h. TH0 receives the

timer clock (the oscillator divided by 12) under the control of TR1only and sets the TF1

flag when it overflows.

3. Timer 1 may still be used in modes 0, 1, and 2, while timer 0 in mode 3with one important

exception: NO interrupts will be generated by timer 1 while timer 0 is using the TF1

overflow flag. Switching timer1 to mode 3 will stop it (and hold whatever count is in timer 1). Timer 1 can be used for baud rate generation for the serial port, or any other mode 0, 1,

or 2 function that doesnt depend on an interrupt (or any other use of the TF1 flag) for

proper operation.

34

RELOAD

TFGOESHIGH

WHENFF 0

XTALOscillator

/12d

TR C/T=0

TL

TH

TF


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2.14 COUNTING:

In the last section we used the timer/counter of the 8051 to generate time delays. These timers can

also be used as counters counting events happening outside the 8051. For the timer/counter when it

is used as a timer, the 8051s crystal is used as the source of frequency. However, when it is used

as a counter, it is a pulse outside of the 8051 that increments the TH, TL register. In counter mode,

the TMOD and TH, TL registers are the same as for the timer. The timers modes are the same as

well.

2.14.1 C/T BIT IN TMOD:

The C/T bit in the TMOD register decides the source of the clock for the timer. If C/T= 0, the timer

gets pulses from the crystal. In contrast, when C/T= 1, the timer is used as a counter and gets its

pulses from outside the 8051. Therefore, when C/T=1, the counter counts up as pulses are fed from

pin 14 and 15. These pins are called T0 (timer 0 input) and T1 (timer 1 input). In the case of timer

0, when C/T= 1, pin3.4 provides the clock pulses and the counter counts up for each clock pulse

coming from that pin. Similarly, for timer 1, when C/T=1 each clock pulse coming in from pin3.5

makes the counter count up.

2.15 8051 SERIAL COMMUNICATION:-

When a microprocessor communicates with the outside world, it provides the data in byte-

sized chunks. In some cases, such as printers, the information is simply grabbed from the 8-bit

data bus and presented to the 8-bit data bus of the printer. This can work only if the cable is not

too long, since long cables diminish and even distort signals. Furthermore, an 8-bit data path is

expensive. For these reasons, serial communication is used. Figure compares serial data

transfer with parallel data transfers.

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FIG 2.16:- SERIAL COMMUNICATION

The fact that in serial communication a single data line is used instead of the 8-bit data line of

parallel communication makes it not only much cheaper but also makes it possible for two

computers located in two different cities to communicate over the telephone.

For serial data communication to work the byte of data must be converted to serial bits using a

parallel-in-serial-out shift register; then it can be transmitted over a single data line. This also

means that at the receiving end there must be a serial-in-parallel-out shift register to receive the

serial data and pack them into a byte. Of course, if data is to be transferred on the telephone

line, it must be converted from 0s and 1s to audio tones, which are sinusoidal-shaped signals.

This conversion is performed by a peripheral device called a modem, which stands for

modulator/demodulator.

2.15.1 METHODS:-Serial data communication uses two methods, asynchronous and synchronous. The synchronous

method transfers a block of data (characters) at a time while the asynchronous method transfers a

single byte at a time. It is possible to write software to use either of these methods, but the

programs can be tedious and long. For this reason, there are special IC chips made by many

36

SENDER RECEIVER

SERIAL TRANSFER

PARALLEL TRANSFER

SENDER

RECEIVER

D7

D0


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manufacturers for serial data communication. These chips are commonly referred to as UART

(Universal asynchronous receiver-transmitter). The 8051 has a built-in UART.

HALF- AND FULL-DUPLEX TRANMISSION

In data transmission if the data can be transmitted and received, it is a duplex transmission. This is

in contrast to simplex transmissions Duplex transmission can be half or full duplex, depending on

whether or not the transfer can be simultaneous. If data is transmitted on way at a time, it isreferred to as half duplex. If data can go both ways at the same time, it is full duplex.

3.12.2 HOW 8051 PERFORMS DATA TRANSFER

The 8051 uses register SBUF to hold data. Register SCON controls data communication, register

PCON controls data rates, and pin RXD (P3.0) and TXD (P3.1) connect to the serial data network.

SBUF is physically two register. One is write only and is used to hold data to be transmitted out of

the 8051 via TXD. The other is read only and holds received data from external sources via RXD.

Both mutually exclusive registers use address 99h.

SERIAL PORT CONTROL(SCON):

37

SIMPLEX TRANSMITTER RECEIVER

HALF DUPLEX TRANSMITTER RECEIVER

RECEIVER TRANSMITTER

FULL DUPLEX TRANSMITTER RECEIVER

RECEIVER TRANSMITTER

FIG 2.17:- SIMPLEX, HALF, AND FULL-DUPLEX

SM0 SM1 SM2 REN TB8 RB8 TI RI


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Bits

7 6 5 4 3 2 1 0 Bit No

TABLE 2.8 SCON REGISTER

BIT SYMBOL FUNCTION

7 SM0 Serial port mode bit0. Set / cleared by programto select mode.

6 SM1 Serial port mode bit0. Set / cleared by programto select mode.

5 SM2 Multiprocessor communication bit. Set/ clearedby program to enable multiprocessor communication

4 REN Receive enable bit.3 TB8 Transmitted bit 8

2 RB8 Receive bit 8

1 TI Transmit interrupt flag.

0 RI Receive interrupt flag.

POWER MODE CONTROL(PCON):

SMOD -------- -------- -------- GF1 GF0 PD IDL

The various pins of PCON register are explained below:-TABLE 2.9 PCON REGISTER

BIT SYMBOL FUNCTION

7 SMOD Serial baud rate modify bit. Set to 1 by program todouble baurd rate using timer1.

6-4 ____ Not implemented

3 GF1 General purpose user flag bit1. Set/cleared byprogram.

2 GF0 General purpose user flag bit0. Set/cleared byprogram.

1 PD Power down bit.

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0 IDL Idle mode bit.

PCON is not bit addressable

2.16 INTERRUPTS:

Occurrence of any disturbance/ intervention within progress of work is called an

Interrupt.

TABLE 2.10: INTERRUPT VERSUS POLLING

INETRRUPTS POLLING

The external/internal circuit generates asignal or request to microcontroller then it

performs the task accordingly.

The microcontroller continuously monitorsthe status of pin/device if the condition ismet, then it perform the task assigned.

If more than one interrupts generate requestto microcontroller then microcontroller executes them sequentially as per definedPRIORITY.

No priority level assignment since it checksall devices in round-robin fashion.

The program which is associated with theinterrupt is called interrupt service routine.

Not such condition.

FIG 2.18: TYPES OF INTERRUPTS

39

INTERRUPTS

MASKABLE NON-MASKABLE

External interruptsTimer interruptsSerial interrupts

RESET


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2.16.1 INTERRUPT SERVICE ROUTINE:

When interrupt is active then microcontroller runs the interrupt service routine.

For every interrupt there is fixed location in program memory that is known as interrupt vector

table.

There are six interrupts in 8051 among them RESET is default interrupt.

TABLE 2.11: INTERRUPT SERVICE ROUTINE

INETRRUPT SOURCE VECTOR ADDRESS

System Reset RST 0000H

External 0 IE0 0003H

Timer 0 TF0 000BH

External 1 IE1 0013H

Timer 1 TF1 001BH

Serial port RI or TI 0023H

2.16.2 WHAT HAPPENS WHEN INTERRUPT OCCURS?

When an interrupt signal comes, the following actions are taken automatically by microcontroller:

1. The current memory location of Program counter saved on to the stack, low byte first.

2. Interrupts of the same and lower priority are blocked.

3. In the case of Timer and External interrupts, the corresponding interrupt flag is cleared.

4. Program execution transfers PC to the corresponding interrupt handle vector address.

5. The interrupt handler routine executes the program.

IE: INTERRUPT ENABLE REGISTER (BIT ADDRESSABLE):

EA ----- ------ ES ET1 EX1 ET0 EX0

EA IE.7 Disables all interrupts if EA=0. If EA=1, interrupt source is individually

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Assembly level language is defined by a set of rules that specify the symbols that can be used

and they may be combined to form a line of code.

The instruction set has a specific format.

[Label:] Mnemonics Operand [; Comment] Name of the label should be meaningful giving the reflection of the code functionality. For

example, LED_ON: label indicates the switch on the led.

First character of a label should be an alphabet. Number of character should not be more than

8 characters.

Reserved words must not be used as label. Mnemonics are assembly opcodes.

For example, MOV

ADDRLC

The operand can be data or address.

Mnemonic can be one byte or more.

Comment begins with semicolon comment indicator. Comments should be small and

meaningful. Assembler ignores comments, but they are indispensable to programmer.

2.17.2 HIGH LEVEL LANGUAGES:High level languages are the language whose instruction set is more compatible with human

languages and human thought processes.

High level languages offer three significant advantages over machine/ assembly language:

1. Simplicity

2. Uniformity

3. Portability

In high level language the programmer do not concern with internal detail of microcontroller.

2.17.3 WHY USE ASSEMBLY LANGUAGE:

There are at least five reasons to write computer instructions in assembly language:

To speed computer operation.

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To reduce the size of the program.

To write programs for special situations.

To save money.

To better understand how computer operate.

Speed, size and uniqueness are advantages assembly language programs offer over high

level languages.

2.17.4 ADDRESSING MODES:

The various ways of accessing data are called addressing modes.

The different addressing modes are:1. Immediate addressing mode.

2. Register addressing mode

3. Direct addressing mode

4. Indirect addressing mode

IMMEDIATE ADDRESSING MODE:

The operand comes immediately after the opcode.

Immediate data must be preceded by the pound (#) sign.

And can be used to load information into any of the register and memory location.

MOV A,#25h

MOV R0,#65h

MOV 30h,#20h

REGISTER ADDRESSING MODE:

This mode involves the use of register to hold the data to be manipulated.

MOV A,R0

MOV R1,A

MOV A,R6

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DIRECT ADDRESSSING MODE:

The data is in Ram memory location and whose address is known.

The address is given as a part of instruction.

MOV 30h, AMOV R0,40h

MOV A,20h

REGISTER INDIRECT ADDRESSING MODE:

A register is used as pointer to data.

As the register holds the address of RAM location they must be preceded by @

sign.

Only register R0, R1 are used for this purpose.

MOV @R1, B; Move contents of register B into RAM location whose address is held by R1.

2.17.5 INSTRUCTION SET:

There are four types of instruction which are used in 8051 programming.

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FIG 2.20:- TYPES OF INSTRUCTION

ARITHMATIC INSTRUCTIONS:

TABLE 2.12: ARITHMATIC INSTRUCTION

MNEMONICS

OPERANDSBYTES/CYCLE

S

ADD A,Rn 1/1ADDC A,Direct 2/1SUBB A,@Ri

A,#data1/12/1

INC A 1/1DEC RN

DIRECT@ Ri

1/12/11/

INC DPTR 1/2MUL AB 1/4DIV AB 1/4DA A 1/1

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LOGICAL INSTRUCTIONS:

TABLE 2.13 LOGICAL INSTRUCTIONS

MNEMONIC OPERANDS BYTES/CYCLE

ANL A,Rn 1/1

ORL A,direct 2/1

XRL A,@RiA,#dataDirect,A

Direct,#data

C,bit

1/12/12/13/2

2/2

CLR A 1/1

DATA TRANSFER INSTRUCTIONS:

TABLE 2.14: DATA TRANSFER INSTRUCTIONS3

MNEMONIC OPERANDS BYTES/CYCLE

MOV A, RnA, DirectA, RiA, #DataRn, A

Rn, DirectRn, #DataDirect, ADirect, RnDirect, DirectDirect, @RiDirect, #data@Ri, A

1/12/11/12/11/1

2/22/12/12/23/22/23/21/1

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@Ri, Direct@Ri, #dataDPTR, #data 16C, bitBit, C

2/22/13/22/12/2

MOVX A, @DPTR @DPTR, AA, @Ri@Ri, A

1/21/21/21/2

MOVC A, @DPTR A, @A+PC

1/21/2

PUSH Direct 2/2

POP Direct 2/2

XCH A, RnA, directA, @Ri

1/12/11/1

XCHD A, @Ri 1/1

BRANCHING INSTRUCTIONS:

TABLE 2.15: BRANCHING INSTRUCTIONS

MNEMONIC OPEARNDS BYTES/CYCLESJC Rel 2/2

JNC Rel 2/2

JB Bit, rel 3/2

JNB Bit, rel 3/2

JBC Bit, rel 3/2

JZ Rel 2/2

JNZ Rel 2/2

LJMP Addr16 3/2

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AJMP Addr11 2/2

SJMP Rel 2/2

JMP @A+DPTR

LCALL Addr16 3/2

ACALL Addr11 2/2

RET -

RETI -

CJNE A, Direct, rel

A, #Data, relRn, #data,rel@Ri, #data, rel

3/2

3/23/23/2

DJNZ Rn, relDirect, rel

2/23/2

NOP - 1/1

2.17.6 PROGRAMMING TOOLS:The different programming tools are Editor, assembler, compiler, emulator etc.

EDITOR:

o Editor provides the facility to write the programs and then immediate assemble or

compile the program.

o Gives us the facility to create new text, open existing text and save the written text.

ASSEMBLER:

o Assembler is software which convert assembly language program in to machine

language program called object code .

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o After assembling the code it generates a number of files.

Asm file Lst file Obj file Link file Hex file

o The program developed by the programmer is stored an ASM file.

o The assembler converts the source file into machine code and produces an object

file and list file.

o The linker links all the object files and produces link file.

o The link file is fed into an OH (object to hex converter) which creates a hex file.

o The hex file is programmed into the ROM.

COMPILER:

o A compiler is a program that translates a high level language program into

machine level instructions.

o A compiler may use an assembly language as an intermediate step in the translation

or may translate the program directly to machine code.

o After assembling the code it generates a number of files like c file, asm file, lst file,

obj file, rel file, link file, hex file etc. depending on the compiler

o The most popular microcontroller compilers are KEIL, SDCC, READS, PIC,

PL/M, from Intel and many more.

PROGRAMMER:

o Programmer is a device used to program the hex file generated by assembler/

compiler into ROM of microcontroller.

o Programmer can be:

ISP Programmer

GANG Programmer

SIMULATOR:

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Transmitter Receiver

CondenserMic Amplifier

Decoder(DTMF) Microcontroller

Outputdevices

I minINDIA

I minAUSTRALIA

Wireless or wired

Real timeglobal call receiver andcontroller

FIGURE 3.1: DTMF OPERATION

Transmitter Receiver

CondenserMic Amplifier

Decoder(DTMF) Microcontroller

I amconnected

msendingDTMF TonesBy pressingkeypad

I mreceivingDTMF tones andsendingtocondenser mic

I mreceivingDTMF tonesand amplifyingit.

I mdecodingcircuit forDTMF toBCD

O/PDevices

Wireless or wired

FIGURE 3.2: DTMF OPERATION

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3.6 COMPONENTS USED

IC USED

8051 MICROCONTROLLER

M8870 DECODER IC

OTHER COMPONENTS

40 PIN & 20 PIN BASE

RESISTANCE(4K,10K,1K)

CAPACITOR(0.1MICROFARAD,1M VARIABLE,22PF)

CRYSTAL OSCILLATOR(11.095Mhz)

LCD,CONNECTING WIRES

3.7 CIRCUIT DIAGRAM

FIGURE 3.3 CONNECTION DIAGRAM

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3.7.1 LED:

The symbol of a LED is shown in figure.

A=ANODEK=CATHODE

FIGURE 3.5: LIGHT EMITTING DIODE

Identification of LED terminals:The cathode terminal of LED is short in length compared to Anode lead and there is a slight flaton the periphery of LEDs.

FUNCTION OF LED:

LED emit light when an electric current passes through them.

LED must have a resistor in series to limit the current as per rating of LED. Otherwise it will

burn out almost instantly.

3.7.2 SEVEN-SEGMENT DISPLAY:

It is made of seven plus one Led.

It is used for displaying number.

TYPES OF DISPLAY:Common Cathode (CC) configuration :

Common Cathode means cathodes of eight LEDs is common. All Leds will glow on applying

1 logic at their segment pins.

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A

K

K A


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3.7.4 POWER SUPPLY

The power supply supplies the required energy for both the microcontroller and the associatedcircuits. It is the most essential part of the circuit because to run its constituent ICs circuit has to

be provided with power. These ICs can run on DC power. Hence the required D.C supply has to be generated. The main parts of a power supply unit and their function are as follows

FIG 3.5: POWER SUPPLY3.7.5 ULN 2004

It is a HIGH VOLTAGE HIGH CURRENT DARLINGTON ARRAYS. It is used to drive relayswhich require high current. in this if we give high signal on input side then we will get low signal

on output side. Its features are:

Output Current to 500 mA

Output Voltage to 95 V

Featuring continuous load current ratings to 500 mA for each of the drivers, the ULN2804 high

voltage, high-current Darlington arrays are ideally suited for interfacing between low-level logic

circuitry and multiple peripheral power loads. Typical power loads totaling over 260 W can becontrolled at an appropriate duty cycle depending on ambient temperature and number of drivers

turned on simultaneously. Typical loads include relays, solenoids, stepping motors, magnetic print

hammers, and heaters. These devices will handle numerous interface needs particularly those

beyond the capabilities of standard logic buffers. These Darlington arrays are furnished in 18-pin

56

D 2

C 1

1 0 0 0 u f

1 N 4 0 0 7 + 5

V

L M 7 8 0 5

1 2

3

V I N V O U T

G

N

D

J 1

12

3

D 3

g n d

D 4

D 1


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dual in-line plastic packages. All devices are pinned with outputs opposite inputs to facilitate ease

of circuit board layout.

3.7.6 RELAY

A relay is an electrically operated switch. Due to this it is also called as

ELECTROMECHANICAL SWITCH made up of electromagnet and having set of contacts inside.

A small current flowing through a coil in relay creates a magnetic field that pulls one switch

contact against or away from another.

Relays allow one circuit to switch to a second circuit which can be completely separated from the

first. In relay there are three main parts:

1. coil

2. spring

3. set of electrical contacts made of metal

WORKING OF RELAY

Current flowing through the coil of the relay creates a magnetic field which attracts a lever and

changes the switch contacts from NC to NO positions. The coil current can be on or off so relays

have two switch positions.

RELAY DRIVER

The coil of a relay needs relatively large current for excitation. So, we require a current driver/amplifier for driving relay. The need can be fulfilled by transistors and for more amplification we

can also use darlington pair. The most common ic no. of darlington pair is ULN 2004/ULN 2804.

PROTECTION OF RELAY

There is generation of residue /stray voltage in reverse polatity across the coil while switching

on/off to the coil current. This voltage may lead to serious effect on working operation of relay.

For prevention , a protection diode (IN4007/IN4148) across the relay coil must be connected.

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3.8 CODING

ORG 0000HLCDPORT EQU P0RS BIT P3.0EN BIT P3.1relay1 bit p3.0relay2 bit p3.1relay3 bit p3.2relay4 bit p3.3

BUZZER BIT P1.0dtmf equ p2

FLAG1 BIT 20H.0FLAG2 BIT 20H.1FLAG3 BIT 20H.2FLAG4 BIT 20H.3SJMP POWER_ON

ORG 0003H ;EXT INT 0RETIORG 000BH ;TIMER 0RETIORG 0013H ;EXT INT 1RETIORG 001BH ; TIMER 1RETIORG 0023H ;SERIAL INTRETI

ORG 0030H

POWER_ON:MOV SP,#70HMOV IE,#00HMOV IP,#00HMOV P0,#0FFHMOV P1,#0FFHMOV P2,#0FFH

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MOV P3,#0FFH

;***************************RAM CLR******************

setb p1.0

RAM_CLR:MOV R0,#7FHCLEAR:

MOV @R0,#00HDJNZ R0,CLEAR

;***************************MAIN*******************

MAIN1:

CLR RELAY2CLR RELAY3

CLR RELAY1CLR RELAY4jnb p2.3,$

MOV R0,#00mov r1,#0

mov r2,#0mov r3,#0

KEYSENSE:;setb p2.0

jnb p2.3,$MOV A,P2ANL A,#11110000BCJNE A,#00010000B,NEXT1SJMP ISHANT1

NEXT1:MOV A,P2ANL A,#11110000BCJNE A,#00100000B,NEXT2aJMP ISHANT2

NEXT2:MOV A,P2ANL A,#11110000BCJNE A,#00110000B,NEXT3aJMP ISHANT3

NEXT3:MOV A,P2

ANL A,#11110000BCJNE A,#01000000B,next4aJMP ISHANT4

NEXT4:

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MOV A,P2ANL A,#11110000BCJNE A,#01010000B,next5clr p2.0

mov p0,#0d0h

acall delaysjmp keysense

next5:MOV A,P2

ANL A,#11110000BCJNE A,#01100000B,next6clr p2.0mov p0,#050h

acall delay

sjmp keysensenext6:MOV A,P2

ANL A,#11110000BCJNE A,#01110000B,next7clr p2.0

mov p0,#097h


next7:MOV A,P2

ANL A,#11110000BCJNE A,#10000000B,keysenseclr p2.0

mov p0,#10h


ISHANT1:clr p2.0mov p0,#0b7hacall delayinc r0cjne r0,#2,deviceclr buzzer

keys:MOV A,P2ANL A,#11110000B

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device4:cpl relay4acall delay

cjne r3,#3,keysense1setb buzzer

mov r3,#0ajmp keysense

ISHANT5:DELAY:

mov r7,#2LP1:

MOV 37h,#255DLP2:

MOV R5,#255DLP3:

NOPDJNZ R5,LP3DJNZ 37h,LP2

djnz r7,LP1RET

3.9 CHARACTERISTICS

Globally applicable

Work in a time constraint

Can be used by deaf and dumb

Not much expensive

Can be applied with auto answering mode at receiver end

Can be used in noisy environment

3.10 APPLICATION

Telecom (Detecting number pressed by user at customer care)

Industries (fire alarm, machines)

Home Appliances (can be connected to any electrical and electronic device)

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3.11 BENEFITS The system is not a time consuming system. In todays world, people are very busy; they dont

want to waste their time.CHAPTER 4:- CONCLUSION

I would like to conclude that the training in the E.M. Tech Foundation gave a though knowledge

about micro controllers & a great chance to learn and understand about embedded systems. This

training increased my knowledge in how micro controllers are useful as well as used in the real

world. I am sure that this training would help me a lot in future.

embedded system ucontrollr

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