Micro Controller Final

8/2/2019 Micro Controller Final

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A

TRAINING REPORT

ON

MICRO CONTROLER

SUBMITTED IN THE PARTIAL FULFILLMENT

FOR THE AWARD OF THE

DEGREE OF BACHELOR OF TECHNOLOGY

IN

ELECTRONICS & COMMUNICATION

Submitted by:

Payal Mittal(1808220)

Submitted to:

Electronics & Communication Department

(BATCH 2008-2010)

Haryana Engineering College,

Jagadhri

(Kurukshetra University, Kurukshetra)


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CERTIFICATE


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ACKNOWLEDGEMENT

Perseverance, inspiration and motivation have always played a key role in any venture. It

is not just the brain that matters most, but that which guides them: The character, the heart,

generous qualities and progressive forces. What was conceived just as an idea materialized

slowly into concrete facts? The metamorphosis took endless hours of toil, had its moments

of frustration, but in the end everything seemed to have sense.

At this level of understanding it is often difficult to understand the wide spectrum of

knowledge without proper guidance & advice. Hence, I take this opportunity to express my

heartfelt gratitude to respected Er. Anurag Goyal who had faith in me and allowed me to

work on the PIC controller. And for his kind co-operation throughout the period of work

undertaken, which has been instrumented in the success of my project and for providing me

the technical knowledge and moral support to complete the work.

I would also like to pay my sincere gratitude to respected Er. Parveen, Head of the

department of Electronics, Haryana Engineering college, Jagadhri for providing me

opportunity to move with such a big corporation.

Last but not the least; I extend my gratitude to the Microsoft. It is only when you make a

presentation, realize the importance of Microsoft Power Point and only when you put

matter in order know the importance of Microsoft Word.

NIKUNJ JAIN

1808247


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INDEX

Chapter 1 : Introduction to Microcontroller

Embedded System

Microcontroller Microcontroller v/s Microprocessor

Chapter 2 : Introduction to 16F877A

PIC Microcontroller

Chapter 3 : Architecture of 16F877A

Special function registers

Option registers

Intcon

Chapter 4 : Memory

Memory organization

Data Memory organization Data EEPROM and Flash Memory

Chapter 5 : Circuit Implementation

Counters

Interrupts

Power Supply

MCLR

Chapter 6 : Timers

Timer 0 Module

Timer 2 ModuleChapter 7 : Light Emitting Diode

Introducing the LED

Resistor

Seven segment display

Conclusion

Bibliography


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LIST OF FIGURES

FIG. NO. DESCRIPTION

1. Pin diagram2. Memory organization3. Timer 0 module4. Timer 2 module5. LED6. Resistor 7. Seven Segment Display


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CHAPTER 1

INTRODUCTION


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1.1 EMBEDDED SYSTEM

An Embedded System is a combination of computer hardware and software, and perhaps

additional mechanical or other parts, designed to perform a specific function. A good

example is the microwave oven. Almost every household has one, and tens of millions ofthem are used every day, but very few people realize that a processor and software are

involved in the preparation of their lunch or dinner.

This is in direct contrast to the personal computer in the family room. It too is comprised

of computer hardware and software and mechanical components (disk drives, for

example). However, a personal computer is not designed to perform a specific function.

Rather, it is able to do many different things. Many people use the term general-purpose

computer to make this distinction clear. As shipped, a general-purpose computer is a

blank slate; the manufacturer does not know what the customer will do with it. One

customer may use it for a network file server, another may use it exclusively for playing

games, and a third may use it to write the next great American novel.

Frequently, an embedded system is a component within some larger system. For example,

modern cars and trucks contain many embedded systems. One embedded system controls

the anti-lock brakes, another monitors and controls the vehicle's emissions, and a third

displays information on the dashboard. In some cases, these embedded systems are

connected by some sort of a communications network, but that is certainly not a

requirement.

At the possible risk of confusing you, it is important to point out that a general-purpose

computer is itself made up of numerous embedded systems. For example, my computer

consists of a keyboard, mouse, video card, modem, hard drive, floppy drive, and sound

cardeach of which is an embedded system. Each of these devices contains a processor

and software and is designed to perform a specific function. For example, the modem is

designed to send and receive digital data over an analog telephone line. That's it. And all

of the other devices can be summarized in a single sentence as well.

If an embedded system is designed well, the existence of the processor and software

could be completely unnoticed by a user of the device. Such is the case for a microwave

oven, VCR, or alarm clock. In some cases, it would even be possible to build an

equivalent device that does not contain the processor and software. This could be done by


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replacing the combination with a custom integrated circuit that performs the same

functions in hardware. However, a lot of flexibility is lost when a design is hard-coded in

this way. It is much easier, and cheaper, to change a few lines of software than to redesign

a piece of custom hardware.

1.1.2 EXAMPLES OF EMBEDDED SYSTEM

DIGITAL WATCH

At the end of the evolutionary path that began with sundials, water clocks, and

hourglasses is the digital watch. Among its many features are the presentation of the date

and time (usually to the nearest second), the measurement of the length of an event to the

nearest hundredth of a second, and the generation of an annoying little sound at the

beginning of each hour. As it turns out, these are very simple tasks that do not require

very much processing power or memory. In fact, the only reason to employ a processor at

all is to support a range of models and features from a single hardware design.The typical

digital watch contains a simple, inexpensive 8-bit processor. Because such small

processors cannot address very much memory, this type of processor usually contains its

own on-chip ROM. And, if there are sufficient registers available, this application may

not require any RAM at all. In fact, all of the electronicsprocessor, memory, countersand real-time clocksare likely to be stored in a single chip. The only other hardware

elements of the watch are the inputs (buttons) and outputs (LCD and speaker). The watch

designer's goal is to create a reasonably reliable product that has an extraordinarily low

production cost. If, after production, some watches are found to keep more reliable time

than most, they can be sold under a brand name with a higher markup. Otherwise, a profit

can still be made by selling the watch through a discount sales channel. For lower-cost

versions, the stopwatch buttons or speaker could be eliminated. This would limit the

functionality of the watch but might not even require any software changes. And, of

course, the cost of all this development effort may be fairly high, since it will be

amortized over hundreds of thousands or even millions of watch sales


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VIDEO GAME PLAYER

When you pull the Nintendo-64 or Sony Playstation out from your entertainment center,

you are preparing to use an embedded system. In some cases, these machines are more

powerful than the comparable generation of personal computers. Yet video game players

for the home market are relatively inexpensive compared to personal computers. It is the

competing requirements of high processing power and low production cost that keep

video game designers awake at night (and their children well-fed).

The companies that produce video game players don't usually care how much it costs to

develop the system, so long as the production costs of the resulting product are low

typically around a hundred dollars.

1.2 MICROCONTROLLER

A microcontroller (or MCU) 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 nterfaces needed for a simple application,

whereas a general purpose microprocessor requires additional chips to provide these

functions.

1.2.1 INTRODUCTION

Circumstances that we find ourselves in today in the field of microcontrollers had their

beginnings in the development of technology of integrated circuits. This development has

made it possible to store hundreds of thousands of transistors into one chip. That was a

prerequisite for production of microprocessors , and the first computers were made by

adding external peripherals such as memory, input-output lines, timers and other. Further

increasing of the volume of the package resulted in creation of integrated circuits. These

integrated circuits contained both processor and peripherals. That is how the first chip


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containing a microcomputer , or what would later be known as a microcontroller came

about.

1.2.2 HISTORY

it was year 1969, and a team of japanese engineers from the busicom company arrived to

united states with a request that a few integrated circuits for calculators be made using

their projects. the proposition was set to intel, and marcian hoff was responsible for the

project. since he was the one who has had experience in working with a computer (pc)

pdp8, it occured to him to suggest a fundamentally different solution instead of the

suggested construction. this solution presumed that the function of the integrated circuit is

determined by a program stored in it. that meant that configuration would be more simple,

but that it would require far more memory than the project that was proposed by japanese

engineers would require. after a while, though japanese engineers tried finding an easier

solution, marcian's idea won, and the first microprocessor was born. in transforming an

idea into a ready made product , frederico faggin was a major help to intel. he transferred

to intel, and in only 9 months had succeeded in making a product from its first

conception. intel obtained the rights to sell this integral block in 1971.

First, they bought the license from the busicom company who had no idea what treasure

they had. During that year, there appeared on the market a microprocessor called 4004.

That was the first 4-bit microprocessor with the speed of 6 000 operations per second. Not

long after that, American company CTC requested from INTEL and Texas Instruments to

make an 8-bit microprocessor for use in terminals. Even though CTC gave up this idea in

the end, Intel and Texas Instruments kept working on the microprocessor and in April of

1972, first 8-bit microprocessor appeard on the market under a name 8008. It was able to

address 16Kb of memory, and it had 45 instructions and the speed of 300 000 operations

per second. That microprocessor was the predecessor of all today's microprocessors. Intel

kept their developments up in April of 1974, and they put on the market the 8-bit

processor under a name 8080 which was able to address 64Kb of memory, and which had

75 instructions, and the price began at $360 microprocessors.


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At the WESCON exhibit in United States in 1975, a critical event took place in the

history of microprocessors. The MOS Technology announced it was marketing

microprocessors 6501 and 6502 at $25 each, which buyers could purchase immediately.

This was so sensational that many thought it was some kind of a scam, considering that

competitors were selling 8080 and 6800 at $179 each. As an answer to its competitor,

both Intel and Motorola lowered their prices on the first day of the exhibit down to $69.95

per microprocessor. Motorola quickly brought suit against MOS Technology and Chuck

Peddle for copying the protected 6800. MOS Technology stopped making 6501, but kept

producing 6502. The 6502 was a 8-bit microprocessor with 56 instructions and a

capability of directly addressing 64Kb of memory. Due to low cost , 6502 becomes very

popular, so it was installed into computers such as: KIM-1, Apple I, Apple II, Atari,

Comodore, Acorn, Oric, Galeb, Orao, Ultra, and many others. Soon appeared several

makers of 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, and Comodore takes over MOS

Technology) which was at the time of its prosperity sold at a rate of 15 million processors

a year!Others were not giving up though. Frederico Faggin leaves Intel, and starts his own

Zilog Inc.In 1976 Zilog announced the Z80.

During the making of this microprocessor, Faggin made a pivotal decision. Knowing that

a great deal of programs have been already developed for 8080, Faggin realized that many

would stay faithful to that microprocessor because of great expenditure which redoing of

all of the programs would result in. Thus he decided that a new processor had to be

compatible with 8080, or that it had to be capable of performing all of the programs

which had already been written for 8080. Beside these characteristics, many new ones

have been added, so that Z80 was a very powerful microprocessor in its time. It was able

to address directly 64 Kb of memory, it had 176 instructions, a large number of registers,

a built in option for refreshing the dynamic RAM memory, single-supply, greater speed

of work etc. Z80 was a great success and everybody converted from 8080 to Z80. It could

be said that Z80 was without a doubt commercially most successful 8-bit microprocessor

of that time. Besides Zilog, other new manufacturers like Mostek, NEC, SHARP, and

SGS also appeared. Z80 was the heart of many computers like Spectrum, Partner,

TRS703, Z-3 .


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In 1976, Intel came up with an improved version of 8-bit microprocessor named 8085.

However, Z80 was so much better that Intel soon lost the battle. Altough a few more

processors appeared on the market (6809, 2650, SC/MP etc.), everything was actually

already decided. There weren't any more great improvements to make manufacturers

convert to something new, so 6502 and Z80 along with 6800 remained as main

representatives of the 8-bit microprocessors of that time.

1.3 Microcontrollers Versus Microprocessors

Microcontroller differs from a microprocessor in many ways. First and the most

important is its functionality. In order for a microprocessor to be used, other components

such as memory, or components for receiving and sending data must be added to it. Inshort that means that microprocessor is the very heart of the computer. On the other hand,

microcontroller is designed to be all of that in one. No other external components are

needed for its application because all necessary peripherals are already built into it. Thus,

we save the time and space needed to construct devices.

A microprocessor contains a control unit, ALU, and Registers

Limited to no I/O

A microcontroller contain a control unit, ALU, Registers, memory, I/O and other

peripherals inside the chip.

Both come in 8, 16, and 32 bit models

Difference is the number of bits that the processor can operate on in one

instruction


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CHAPTER 2

INTRODUCTION TO

16F877A


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2.1 THE PIC MICROCONTROLLER

Although microcontrollers were being developed since early 1970' s real boom

came in mid 1990' s. A company named Microchip made its first simple microcontroller,which they called PIC. Originally this was developed as a supporting device for POP

computers to control its peripheral devices, and therefore' named as PIC, Peripheral

Interface Controller. Thus all the chips developed by Microchip have been named as a

class by themselves and called PIC. Microchip itself does not use this term anymore to

describe their microcontrollers, however use PIC as part of product name. they call their

products MCU's.

A large number of microcontroller designs are available from microchip.

Depending upon the architecture, memory layout and processing power. They have been

classified as low range, mid range, high range and now digital signal processing

microcontrollers.

The beauty of these devices is their easy availability, low cost and easy

programming and handling. This has made PIC microcontrollers as the apple of hobbyists

and students eyes. We shall be talking about mid-range PIC microcontrollers, and use

PIC16F877A rototype in this manual to explore them. Knowledge gained by learning and

exploring one microcontroller is almost 90% applicable on other microcontrollers of the

same family The only difference is in availability of resources on different chips. General

organization of PIC Microcontrollers. Although we shall talk in detail on various aspect of

these chips in relevant sections, here I would like to give a brief introduction on the overall

business involved.

Fig shows the pin out details of a very popular 40 pin In PIC microcontroller,

PIC16F877, as you can see that each pin has been assigned a number of functions.

Sometimes two and sometimes three. This situation is very common in microcontroller, as

there is always more which your microcontroller


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Can offer, yet the number of pins on a given package is limited. In a given

circuit/application a pin is usually tied to a specific job, and all functionality q a pin is

usually not required, however you make opt to use the specific pin your own way.

The specific function of a pin is selected by configuring various bits of internal

registers. The number and names of these special function registers (SFRs) vary from

device to device as some devices have limited functionality while others have more.

Nevertheless if we are talking about a function which is present in both devices, its SFR

will be same. The selection and settings of these SFR's is the key to successful

programming. It is therefore mandatory to go through the data sheets of the device before

starting a project.

Second important thing to know is that the devices with same number of R

microchip), are all pin-compatible. Which means if you design a project four Pin PIC

microcontrol1er, and later want to replace the chip with another 40 pin PIC microcontroller

are all compatible. It is also good to know that a pin labeled as lets say RBO is plotted, on

pin 33 of PIC l6F877, but the same pin is available on pin 6 in 18 pin PIC1F628 the pins

are functionally same, as long as their names are same. So if you develop all a project

while experimenting on. 18F452 using pin RBO, after successful testing you want to


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transport the project to an 18 pm device, which also has RBO on It, apart form pin number

on package, and recompiling the program, you don have to bother much about anything

else.


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CHAPTER 3

ARCHITECTURE OF

16F877A


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3.1 SPECIAL FUNCTION REGISTERSThe Special Function Registers are registers used by the CPU and peripheral

modules for controlling the desired operation of the device. These registers areimplemented as static RAM. A list of these registers is given in Table 2-1. The Special

Function Registers can be classified into two sets: core (CPU) and peripheral. Thoseregisters associated with the core functions are described in detail in this section. Thoserelated to the operation of the peripheral features are described in detail in the peripheralfeatures section.


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3.2 OPTION_REG REGISTER

The OPTION_REG Register is a readable and writable register, which contains various

control bits to configure the TMR0 prescaler/WDT postscaler (single assignable register

known also as the prescaler), the external INT interrupt, TMR0 and the weak pull-ups on.

PORTB.


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3.3 INTCON REGISTER

The INTCON register is a readable and writable register,which contains various enable and

flag bits for the TMR0 register overflow, RB port change and external RB0/INT pininterrupts.


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CHAPTER 4

MEMORY


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4.1 MEMORY ORGANIZATION

There are three memory blocks in each of the PIC16F87XA devices. The program memory

and data memory have separate buses so that concurrent access can occur

and is detailed in this section. Data Eeprom And Flash Program Memory.

Fig.-

Memory organization


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The PIC16F87XA devices have a 13-bit program counter capable of addressing an 8K

word x 14 bit program memory space. The PIC16F876A/877A devices have 8K words x

14 bits of Flash program memory, while PIC16F873A/874A devices have 4K words x 14

bits. Accessing a location above the physically implemented address will cause a

wraparound.

The Reset vector is at 0000h and the interrupt vector is at 0004h.


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4.2 DATA MEMORY ORGANIZATION

The data memory is partitioned into multiple banks which contain the General

Purpose Registers and the pecial Function Registers. Bits RP1 (Status) and RP0

(Status) are the bank select bits. Each bank extends up to 7Fh (128 bytes).

The lower locations of each bank are reserved for the Special Function Registers.

Above the Special Function Registers are General Purpose Registers, implemented as static

RAM. All implemented banks contain Special Function Registers. Some frequently used

Special Function Registers from one bank may be mirrored in another bank for code

reduction and quicker access.


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4.3 DATA EEPROM AND FLASH PROGRAM MEMORY

Although there are many models of microcontrollers in the PIC family, they all

share some common features, such as program memory, data memory, I/O ports, andtimers..The data EEPROM and Flash program memory is readable and writable during

normal operation (over the full VDD range). This memory is not directly mapped in the

register file space. Instead, it is indirectly addressed through the Special Function

Registers. There are six SFRs used to read and write this memory:

EECON1

EECON2

EEDATA

EEDATH

EEADR

EEADRH

When interfacing to the data memory block, EEDATA holds the 8-bit data for

read/write and EEADR holds the address of the EEPROM location being accessed.

These devices have 128 or 256 bytes of data EEPROM (depending on the device),

with an address range from 00h to FFh. On devices with 128 bytes, addresses from 80h to

FFh are unimplemented and will wraparound to the beginning of data EEPROM memory.

When writing to unimplemented locations, the on-chip charge pump will be turned off.

When interfacing the program memory block, the EEDATA and EEDATH

registers form a two-byte word that holds the 14-bit data for read/write and the EEADR

and EEADRH registers form a two-byte word that holds the 13-bit address of the program

memory location being accessed. These devices have 4 or 8K words of program Flash,

with an address range from 0000h to 0FFFh for the PIC16F873A/874A and 0000h to

1FFFh for the PIC16F876A/877A. Addresses above the range of the respective device will

wraparound to the beginning of program memory.

The write/erase voltages are generated by an on-chip charge pump, rated to operate

over the voltage rangeof the device for byte or word operations.


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4.3.1 REGISTERS LINKING TO MEMORY OPERATION


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CHAPTER 5

CIRCUIT

IMPLEMENTATION


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5.1 COUNTERS

If a timer is supplied with pulses over the microcontroller input pin then it turns into a

counter, clearly, it is about the same electronic circuit. The only difference is that in thiscase pulses to be counted come through the ports and their duration (width) is mostly not

defined. That is why they cannot be used for time measurement, but can be used to measure

anything else: products on an assembly line, number of axis rotation, passengers etc.

(depending on sensor in use).

Watchdog Timer

As name itself indicates a lot about its purpose. Watchdog Timer is a timer

connected to a completely separate RC oscillator within the microcontroller.

If the watchdog timer is enabled, every time it counts up to end, the microcontroller

reset occurs and program execution starts from the first instruction. The point is to prevent

this from happening by using a specific command. The whole idea is based on the fact that

every program is executed in several longer or shorter loops.

If instructions which reset the watchdog timer are set on the appropriate program

locations, besides commands being regularly executed, then the operation of watchdog

timer will not affect program execution. If for any reason (usually electrical noises in

industry), the program counter "gets stuck" on some memory location from which there is

no return, the watchdog will .not be cleared and there registers value being constantly

incremented will reach the maximum! Reset occurs .


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5.2 INTERRUPTS

The subject of interrupts is probably' be the longest and most difficult to go

through. There is no easy way of explaining interrupts, but hopefully by the end of thissection you will be able to implement interrul1t into your own programs. We have split the

section into two parts. This is to help break the subjects up, and to give you, a break. So

what is an interrupt? Well, as the name suggest an interrupt is a process or a signal that

stops a microprocessor/microcontroller. What it is doing so that something else can happen.

Let me give you an every day example. at home, chatting to someone. Suddenly the

telephone rings. You stop chatting and pick up the telephone to speak to the caller. When

you have finished your telephone conversation, you go back to chatting to the person

before telephone rang. You can think of the main routine as you chatting to person before

the telephone ringing causes you to interrupt your chatting, and the interrupt routine is the

process of talking on the telephone. When the telephone conversation has ended, you then

back to your main routine of chatting. This example is exactly how an interrupt ca~

processor to act. The main program is running, performing some function in a circuit, but

when an interrupt occurs the main program halts while another routine is carried out. When

this routine finishes, the processor goes back to the main routine again. The PIC has 4

sources of interrupt. They can be split into two groups. Two are sources of interrupts that

can be applied externally to the PIC, while the other two are internal processes. We are

going to explain the two external ones here. The other two will be explained in timers and

storing data.

If you look at the pin-out of the PIC, you will see that pin 33 shows it is RBO/INT.

Now, RBO is obviously Port B bit O. The INT symbolizes that it can also be configures as

an external interrupt pin. Also, Port B bits 4 to 7 can also be used for interrupts. Before we

can use the INT or other Port B pins, we need to do two things. First we need to tell the

PIC that we are going to use interrupts. Secondly, we need to specify which port B pin we

will be using as an interrupt and not as an I/O pin.


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Inside the PIC there is a register called iNTCON, and is at address 0Bh. Within this register

there are 8 bits that can be enabled or disabled. Bit 7 of INTCON is called GIE. This is the

Global Interrupt Enable. Setting this to I tells the PIC that we are going to use an interrupt.

Bit 4 of INTCON is called INTE, which means interrupt Enable. Setting this bit to I tells

the PIC that RBO will be an interrupt pin. Setting bit 3, called RBIE, tells the PIC that we

will be using Port B bits 4 to 7. Now the PIC knows when this pin goes high or low, it will

need to stop what it's doing and get on with an interrupt routine. Now, we need to tell . IC

whether the interrupt is going to be on the rising edge (OV to +5V) or the falling edge

(+5Vto 0V) transition of the signal. In other words, do we want the PIC to interrupt when

the signal goes from low to high, or from high to low. By default, this is set up to be on the

rising edge. The edge 'triggering' is set up in another register called the OPTION register, at

address 81 h. The bit we are interested in is bit 6, which is called INTEDG. Setting this to 1

will cause the PIC to interrupt on the rising edge (default state) and setting it because the

PIC to interrupt on the falling edge. If you' want the PIC to trigger o~ the edge, then you

don't need to do anything to this bit.

Ok, so now we have told the PIC which pin is going to be the interrupt, and on

which edge to trigger, what happens in the program and the PIC when interrupt occurs?

Two things happen. First, a 'flag' is set. This tells the internal processor of the PIC that an

interrupt has occurred. Secondly, the program counter which points to a particular address

within the PIC. Let's quickly look at each of these separately.

Interrupt Flag

In our INTCON register, bit 1 is the interrupt flag, called INTF. Now when any

interrupt occurs, this flag will be set to 1 while there isn't an interrupt, the flag is set to O.

And that is all it does. Now you are probably thinking 'what is the point? Well, while this

flag is set to the PIC cannot, and. will ~, pond to any other interrupt. So, let say that we use

an interrupt. The flag will be 1, and the PIC will go to our routine for processing the

interrupt. If this flag was not set to 1, and the PIC was allowed to keep responding to the

interrupt, then continually pulsing the pin will keep the PIC going back to the start of our

interruption routine will never finishing it. Going back to my example of telephone, it's like


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picking up the telephone, and Just as soon as you start to speak It starts ringing again

because someone else want to talk to you. It is far better to finish one conversation, then

pick up the phone again to talk to the second person.

There is a slight drawback to this flag. Although the PIC automatically sets this flag to 1; it

doesn't set it back to 0! That ,task has to be done by the programmer - i.e. you. This is

easily done, as We are sure you can guess, and has to be done after the PIC has executed

the interrupt routine.

5.3 POWER SUPPLY

PIC Microcontroller use TTL Logic, and therefore expect a well regulated 5V

power supply. The supply may however range from 3.5 V to 5.5 V. These icrocontrollers

require very small amount of current. Indeed these devices have been labeled as nano-watt

technology devices. The logical levels are also same, a signal from 0 to about 2 V is

considered as logical 0 and a signal from 3.5 V to 4.5 V is considered as logical 1. In

order to communicate with devices using higher logical voltages, consider level

conversion.

5.4 MCLR, MASTER CLEAR


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On every PIC microcontroller you will find a pin labeled as MCLR. This pin has

two basic functions. It is used to reset the microcontroller, like soft boot. As well as to put

the microcontroller into programming mode.

The MCLR pin when connected to ground, will reset the microcontroller, and keep

it in reset the microcontroller state, till the ground connection is released. After that the

microcontroller will have all its RAM reset, and program execution will begin, just like the

system has been just powered on. A 1OK pull up resistor is usually connected with the pin

to keep it high when reset switch is released.

The same pin will also work as program mode pin. When a new software is to be

downloaded into the microchip by your programming device. This can be done right in

your circuit, or by taking the IC out of circuit and putting it into the IC socket on your

programmer. We shall talk more about this in section on programming.


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CHAPTER 6

TIMERS


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6.1 TIMER0 MODULE

The Timer0 module timer/counter has the following features:

8-bit timer/counter

Readable and writable

8-bit software programmable prescaler

Internal or external clock select

Interrupt on overflow from FFh to 00h

Edge select for external clock

The Timer0 module and the prescaler shared with the WDT. Additional information

on the Timer0 module is available in the PICmicro Mid-Range MCU Family Reference

Manual (DS33023). Timer mode is selected by clearing bit T0CS (OPTION_REG). In

Timer mode, the Timer0 module will increment every instruction cycle (without prescaler).

If the TMR0 register is written, the increment is inhibited for the following two instruction

cycles.

The user can work around this by writing an adjusted value to the TMR0 register.

Counter mode is selected by setting bit T0CS (OPTION_REG). In Counter mode,Timer0 will increment either on every rising or falling edge of pin RA4/T0CKI. The

incrementing edge is determined by the Timer0 Source Edge Select bit, T0SE

(OPTION_REG). Clearing bit T0SE selects the rising edge. Restrictions on the

external clock input are discussed in detail in Section Using Timer0 with an External

Clock.

The prescaler is mutually exclusively shared between the Timer0 module and the

Watchdog Timer. The prescaler is not readable or writable. Section Prescaler details the

operation of the prescaler. Timer0 Interrupt The TMR0 interrupt is generated when the

TMR0 register overflows from FFh to 00h. This overflow sets bit TMR0IF (INTCON).

The interrupt can be masked by clearing bit TMR0IE (INTCON). Bit TMR0IF must be


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cleared in software by the Timer0 module Interrupt Service Routine before re-enabling this

interrupt. The TMR0 interrupt cannot awaken the

processor from Sleep since the timer is shut-off during Sleep.

6.2 TIMER2 MODULE

Timer2 is an 8-bit timer with a prescaler and a postscaler. It can be used as the

PWM time base for the PWM mode of the CCP module(s). The TMR2 register is readable

and writable and is cleared on any device Reset. The input clock (FOSC/4) has a prescale

option of 1:1, 1:4 or 1:16, selected by control bits T2CKPS1:T2CKPS0 (T2CON).

The Timer2 module has an 8-bit period register, PR2. Timer2 increments from 00h until it

matches PR2 and then resets to 00h on the next increment cycle. PR2 is a readable and

writable register. The PR2 register is initialized to FFh upon Reset. The match output of

TMR2 goes through a 4-bit postscaler (which gives a 1:1 to 1:16 scaling inclusive) to

generate a TMR2 interrupt (latched in flag bit, TMR2IF (PIR1)). Timer2 can be shut-


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off by clearing control bit, TMR2ON (T2CON), to minimize power consumption.

Register 7-1 shows the Timer2 Control register. Additional information on timer modules

is available in the PICmicro Mid-Range MCU Family Reference Manual (DS33023).

6.2.1 Timer2 Prescaler and Postscaler


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The prescaler and postscaler counters are cleared when any of the following occurs:

a write to the TMR2 register

a write to the T2CON register

any device Reset (POR, MCLR Reset, WDT

Reset or BOR TMR2 is not cleared when T2CON is written. 7.2 Output of TMR2

The output of TMR2 (before the postscaler) is fed to the SSP module, which optionally

uses it to generate the shift clock.


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CHAPTER 7

LIGHT EMITTING

DIODE (LED)


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7.1 INTRODUCING THE LED

A diode is a one-way current valve, and a light emitting diode (LED) emits light

when current passes through it. Unlike the color codes on a resistor, the color of the LEDusually just tells you what color it will glow when current passes through it. The important

markings on an LED are contained in its shape. Since an LED is a one-way current valve,

you have to make sure to connect it the right way, or it wont work as intended.

Fig. shows an LEDs schematic symbol and part drawing. An LED has two

terminals. One is called the anode, and the other is called the cathode. In this activity, you

will have to build the LED into a circuit, paying attention to make sure the leads connected

to the anode and cathode are connected to the circuit properly. On the part drawing, the

anode lead is labeled with the plus-sign (+). On the schematic symbol, the anode is the

wide part of the triangle. In the part drawing, the cathode lead is the unlabeled pin, and on

the schematic symbol, the cathode is the line across the point of the triangle.

7.2 LED BUILDING AND TESTING THE LED CIRCUIT

Its important to test components individually before building them into a larger

system. This activity focuses on building and testing two different LED circuits. The first

circuit is the one that makes the LED emit light. The second circuit is the one that makes it

not emit light. In the activity that comes after this one, you will build the LED circuit into a

larger system by connecting it to the BASIC Stamp. You will then write programs that

make the BASIC Stamp cause the LED to emit light, then not emit light. By first testing


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each LED circuit to make sure it works, you can be more confident that it will work when

you connect it to a BASIC Stamp.

7.3 INTRODUCING THE RESISTORA resistor is a component that resists the flow of electricity. This flow of

electricity is called current. Each resistor has a value that tells how strongly it resists

current flow. This resistance value is called the ohm, and the sign for the ohm is the Greek

letter omega: The resistor you will be working with in this activity is the 470 resistor

shown in Figure

. The resistor has two wires (called leads and pronounced leeds), one coming out of each

end. There is a ceramic case between the two leads, and its the part that resists current

flow. Most circuit diagrams that show resistors use the jagged line symbol on the left to tell

the person building the circuit that he or she must use a 470 resistor. This is called a

schematic symbol. The drawing on the right is a part drawing used in some beginner level

Stamps in Class texts to help you identify the resistor in your kit.

Resistors like the ones we are using in this activity have colored stripes that tell you

what their resistance values are. There is a different color combination for each resistance

value. For example, the color code for the 470 resistor is yellow-violet-brown. There

may be a fourth stripe that indicates the resistors tolerance. Tolerance is measured in

percent, and it tells how far off the parts true resistance might be from the labeled

resistance. The fourth stripe could be gold (5%), silver (10%) or no stripe (20%). For the

activities in this book, a resistors tolerance does not matter, but its value does. Each color


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bar that tells you the resistors value corresponds to a digit, and these colors/digits are listed

in Table Figure shows how to use each color bar with the

table to determine the value of a resistor.

Here is an example that shows how Table and Figure can be used to figure out a

resistor value by proving that yellow-violet-brown is really 470 :

7.4 WHATS A 7-SEGMENT DISPLAY?

A 7-segment display is rectangular block of 7 lines of equal length that can be lit

selectively to display digits and some letters. A very common form is the 7-segment LED

display, a package with a rectangular block of 7 LEDs. Figure shows a part drawing of the

7-segment LED display you will use in this chapters activities. It has one additional LED,

a dot that can be used as a decimal point. Each of the segments (A through G) and the dot

contains a separate LED, which can be controlled individually.

Most of the pins have a number along with a label that corresponds with one of the

LED segments. Pin 5 is labeled DP, which stands for decimal point. Pins 3 and 8 are

labeled common cathode, and they will be explained when the schematic for this part is

introduced.


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Figure shows a schematic of the LEDs inside the 7-segment LED display. Each

LED anode is connected to an individual pin. All the cathodes are connected together by

wire inside the part. Because all the cathodes share a common connection, the 7-segment

LED display can be called a common cathode display. By connecting either pin 3 or pin

8 of the part to Vss, you will connect all the LED cathodes to Vss.


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CONCLUSION

I Would Like To Say That I Was Given A Great Chance To Study, Understand And

Learn About The Embedded Systems. and got a great opportunity to learn about a

industrial controller (PIC ) ,which is massively used all over the world on an average of

about 69 %.so , would like to thank my college to include this training as a part of studies,

Apart from the great chance to develop it also act as a great source of inspiration

and Motivation for all of us inside and out


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REFERENCES

Websites :

www.microchip.com

www.enwikipedia.org

www.ccsinfo.com
http://www.microchip.com/http://www.enwikipedia.org/http://www.ccsinfo.com/http://www.microchip.com/http://www.enwikipedia.org/http://www.ccsinfo.com/

Documents

Micro Controller Final