micro intro lecture 2

7/27/2019 Micro Intro Lecture 2

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Microprocessors- Evolution &

Introduction to 8085

Oxford University Press 2013. All rights reserved.


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Introduction

Microprocessor is an electronic chip that functions asthe central processing unit (CPU) of a computer

In other words, we can call microprocessor as the heartof an com uter s stem.

Some may call the microprocessors as the brain of thecomputers.

The microprocessor based systems with limited

resources are called as microcomputers. Now-a-days microprocessors are found in almost all

electronic machines and appliances in its different form

Oxford University Press 2013


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Introduction

Some common devices using microprocessors arecomputer printers, automobiles, washing machines,microwave ovens, mobile phones, fax machines, Xeroxmachines and advanced instruments like radar,

, .,

Any middle class house-hold will have about a dozensmicroprocessor in different forms inside variousappliances.

The recent developments in electronic industry and thelarge scale integration of devices has led to rapid costreduction and more and more application ofmicroprocessors and its derivatives.



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Introduction

Almost all microprocessors use the basic concept ofstored program execution.

By this concept, programs or the instructions to be

executed by the microprocessor are stored sequentiallyin memory locations.

The microprocessor or the processor in general will

fetch the instructions one after the other and executethem it in its arithmetic and logic unit.



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Introduction

A microprocessor can be programmed to do any taskthat can be written and programmed by the user.

So, in order to work with the microprocessor, it isnecessar for the user to know about the internal

resources and features of the microprocessor. The programmers must also understand the

instructions that a microprocessor can support.

Every microprocessor will have its own associated setof instructions that it supports and this list is given byall the microprocessor manufacturers



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Introduction

The instruction set for microprocessors is given in twoformsa) one in mnemonic which is comparatively easy tounderstand


b the other in binary machine code which themicroprocessor really works upon and difficult to understandby us.

Programs are written using mnemonics called theassembly level language and then they are convertedinto binary machine level language.

This conversion can be done manually or using anapplication called assembler.


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Introduction

In general, the programs are written by the user fora microprocessor to work with real world data.

These data are available in many forms and are


.

To give this data to the microprocessor, themicroprocessor based systems need some inputinterfacing circuits and some electronic processing

circuits. These circuits include data converters and ports


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Introduction

After processing the real world data, the output fromthe microprocessor must be taken out to give to final

end effect instrument or circuits.


This again needs interfacing circuits and ports. So, a microprocessor based system will need a set of

memory units, set of interfacing circuits for inputs and

a set of interfacing circuits for outputs.


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Introduction

All circuits put together along with microprocessor arecalled as microcomputer system.


are in general called as hardware.

The program which makes this hardware useful is

called as software.


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Basic terms

Chipa) A chip or an integrated circuit is a small, thin

piece of silicon with the required circuit and


transistors etched on it to perform a particularfunction.

b) Simpler processors might consist of a few

thousand transistors etched onto a silicon base justa few millimeters square.


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Basic terms Bit

a) A bit means a single binary digit.

b) Also, the bit is the fundamental storage unit ofcom uter memor . In binar bit can have onl two


values, 0 or 1, whereas a decimal digit can have 10values, represented by symbols 0 through 9.

Bit Size

The bit size of a microprocessor refers to the numberof bits that can be processed simultaneously by thebasic arithmetic circuits of the microprocessor.


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Basic terms

WordA number of bits grouped together for processing is

called as word. In microprocessors, the word in


z z

processed by the ALU of the processor. 16-bit binary

number is called a word in a 16-bit processor.

Memory word

The number of bits that can be stored in a register of

memory element is called a memory word. Mostly all

memory units use 8-bits as their memory word.


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Basic terms

Byte

An 8-bit word is referred to as a byte

Nibble


-

Kilobyte

A collection of 1024 bytes is called a kilobyte (210bytes)

Megabyte

A collection of 1024 Kbytes is called a megabyte (220bytes)


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Basic terms

RAM or R/W memorya) Random Access Memory or Read/ Write memory isthe type of semiconductor memory in which a particularmemor location can be erased and written with a new


data at any time.b) These memory units are volatile, which means thatthe content of the memory is erased when the power tothe chip is disrupted.

c) The access of the individual memory location can bedone randomly. In microprocessors, the RAM is used tostore data.


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Basic terms

DRAMa) Dynamic Random Access Memory is a

semiconductor memory in which the stored


contents need to be refreshed repeatedly at aboutthousands of times per second.

b) Without refreshing, the stored data will be lost.

c) These memory chips are preferred in a computersystem because it is economical although slower.


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Basic terms SRAM

Static Random Access Memory chips keep the datastored in it as long as power is available. There is no

need for refreshin . In terms of s eed SRAM is


faster.

ROM

Read Only Memory are memory devices whose

contents are retained even after removing thepower supply.


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Basic terms Arithmetic and Logic Unit (ALU)

a) ALU is a digital circuit present in the microprocessor

to do performs arithmetic and logic operations on


.

b) The typical operations performed by the ALU are

addition, subtraction, Logical AND, logical OR and

comparison of binary data.

c) Generally, the functions of the ALU of a

microprocessor will decide the functionality that can

be performed by the processor.


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Basic terms

Microcontroller

Microcontroller is a chip that includes microprocessor,memory and I/O signal ports. Microcontrollers can becalled as sin le chi microcom uters.


MicrocomputerThe system formed by interfacing microprocessor withmemory, and I/O devices to work with the required

program is called microcomputer. Bus

The bus in a microprocessor system refers to a groupof wires or signals having a common functionality


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Basic terms System Bus

The System bus is a group of signals used for

communication between the microprocessor and


.

Firmware

Software written for a microprocessor application

without provision for changes. These are stored into

permanent storage or ROM of the computer system.


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Basic terms Input device

The devices that are used for giving data to themicrocomputer system are called as input devices.Usuall ke board and mouse are the in ut devices


through which data and instructions are given tocomputer.

Output device

The devices that are used for getting data out fromthe microprocessor or microcomputer system arecalled as output devices. A display screen, printer anddisplays are the common output devices.


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Basic terms Floppy disk

A removable type magnetic disk used for storing

programs and data from and to the computer.


s r ve

The hardware component that is used to read or write

to data to devices such as a floppy disk.

Computer architecture

The design and internal configuration and accesses in

a digital computer


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Basic terms Von-Neumann Architecture

The architecture in which the same memory is used

for storing the program as well as data.


The architecture in which the program and data are

stored in two separate memory units.

CISC Processor

Complex Instruction Set Computer, is a processor

architecture that supports many number of machine

language instructions.


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Basic terms RISC processor

a) Reduced Instruction Set Architecture, is aprocessor architecture that supports limited or smallnumber of machine language instructions.


b) RISC processors are expected to execute theprograms faster than CISC processors.

High level Language

a) A computer programming language in which

programs are written without the knowledge of theprocessor in which the program will be executed.

b) BASIC, FORTRAN, C, PASCAL and JAVA are theexamples of high level languages.


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Basic terms Assembly Language

a) A programming language written using the

mnemonics or the instruction set of a particular

micro rocessor.


b) Assembly language programming is microprocessorspecific.

c) It cannot be easily understood like a high level

language program.

d) But these are easier than machine language

program.


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Basic terms Machine Language

a) The binary code programs that are specific to theprocessor and can be directly executed by the

rocessor.


b) The machine language is the lowest level programand cannot be easily understood.

Assembler

A computer application program that converts theassembly language program into machine levellanguage program.


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Basic terms Compiler

A computer program that converts the high level

language program into machine level language


.

Interpreter

a) A computer program that reads the high level or

assembly level program one line at time and converts

that into machine level program.

b) Compiler and assembler can function only on the

entire program in a file.


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Basic terms Algorithm

a) A sequence of operations or instructions that

defines how to solve a problem using a computer or


.

b) An algorithm must be definite and follow a clear

instruction flow without any ambiguity and must have

a definite starting and end point.


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Basic terms

BIOSa) Basic Input/ Output System is a set of programthat handles the input and output functions and


nteracts w t t e ar ware rect y.b) A new hardware installed must be providedwith the corresponding BIOS routines.


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Basic terms Clock

a) The circuit in the computer that generates the

sequence of evenly spaced pulses to synchronize the

activities of the rocessor and its eri herals.


b) The clock speed determines the speed of theoperation of the computer.

c) The computer with a high frequency clock works

faster. Normally the clock frequency is in the range ofMega Hertz, MHz or Giga Hertz, GHz.


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Basic terms MIPS

"Millions Instructions per Second" is a measure of thespeed at which the instructions are executed in aprocessor.


Tri-state logica) Three Logic Levels used are High (1), Low (0), Highimpedance state (Z).

b) The logic high state of digital circuit can source currentand a logic low can sink current in a computer system.

c)But high impedance state neither sources current andnor sinks current and so the other devices connected to itare not affected.


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Basic terms Operating System

a) The program that controls the entire computer and itsresources and enables users to access the computer and itsresources.


n er e con ro o e opera ng sys em, e compu er

recognizes and obeys commands typed by the user.

c) In addition, the operating system provides built-inroutines that allow the users program to perform input-output operations without specifying the exact hardwareconfiguration of the computer.

d) In low level microprocessor based systems, the programthat controls the hardware is called as monitor routines or

monitor software.


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Types of Processors Two types of processors are manufactured

a) the microprocessor

b) the microcontroller


e genera purpose m croprocessors g ve ecomputers all the necessary computing power.

These microprocessors need additional circuitry

elements such as memory devices, I/O ports to connect

the input and output devices.

All microprocessor based systems need two types of

memories RAM and ROM.


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Microcontrollers The microcontrollers are the microprocessors designed

especially for control applications.

Microcontrollers contain memory units and I/O ports

inside a chi in addition to the CPU art.


Microcontrollers are otherwise called as embeddedcontrollers are generally used to control and operate

smart machines.

Some of the machines using microcontrollers aremicrowave ovens, washing machines, sewing machines,

automobile ignition systems, computer printers and fax

machines etc.


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Microcontrollers

Out of 100 processor chips manufactured, 99 areembedded processors and remaining 1 processor

alone goes into general computers.


ots o sem con uctor compan es are n t e mar et o

microcontrollers and any application development

engineer is flooded with the variety of

microcontrollers as the choice.


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The system consists of CPU, memory and I/O ports

The interfacing of the processor with the other partsof the microcomputer system needs three bus

Microprocessor based system


architecture. The three buses are

a) data bus,

b) address bus

c) control bus


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Each memory location or I/O port is identified by a

specific address similar to the postal address.

Here, in microprocessor systems, the addresses are all in


format.

The address is a unique pattern used to identify alocation in memory or I/O port.

The address bus consists of many lines that can have thedigital data sent by the processor.


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An address bus of 8 bits 28

different memory locations. Similarly, the 16-bit address bus can address 216

different addresses. Its address ranges from 0000H to


FFFFH.

The higher the number of lines of address bus is, the

more the locations the processor is able to manage.


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A control bus is needed for proper data transfer

between the processor and other peripherals.

The control bus basically consists of signals like selectingthe ro er memor or I O device from the address


signal to indicate the direction of data transfer; and thesignal to synchronize data transfer between slowdevices.


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Origin of Microprocessor

The breakthrough in transistor technology led to theintroduction of minicomputers of the 1960s and the

personal computer revolution of the 1970s.


Intel was the first MPU producer and has been holding a

large share in the world market of this product.

Microprocessors evolution is categorized into five

generations

first, second, third, fourth, and fifth generations.


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First Generation (1971-73)

The microprocessors that were introduced in 1971 to1972 were referred to as the first generation systems.

Intel Corporation introduced 4-bit 4004 at 108 kHz, the


first microprocessor in 1971, co-developed by Busicom,

a Japanese manufacturer of calculators.

In 1972, Intel made the 8-bit 8008 and 8080

microprocessors.


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Second Generation (1974-78)

Very large-scale integration (VLSI) lead to chips which

had speeds up to hundreds of millions of switching persecond.

The second eneration marked the be innin of ver


efficient 8 bit microprocessors. Some of the popular processors were Motorolas 6800

and 6809 and Intels 8085, Zilogs Z80.

The distinction between the first and second generationdevices was primarily the use of newer semiconductortechnology to fabricate the chips.

They were manufactured using NMOS technology.


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Third Generation (1979-80) Introduced in 1978, dominated by Intels 8086 and the

Zilog Z8000, which were 16-bit processors withminicomputer-like performance, have 16-bit arithmeticand pipelined instruction processing.


, .

Motorolas MC68020, incorporated an on-chip cache forthe first time and the depth of the pipeline increased tofive or more stages.

HMOS - speed-power-product of HMOS is four timesbetter than that of NMOS.

HMOS can accommodate twice the circuit densitycompared to NMOS.


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Fourth Generation (1981-95)

Designs with more than a million transistors in a

package.

32 bits microprocessors introduced Intel 80386 and


otoro a .

Fabricated using low-power version of the HMOS

technology called HCMOS.


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Fifth Generation (1995 till date)

Employed decoupled super scalar processing.

Chips carry on-chip functionalities and improvementsin the speed of memory and I/O devices


Des gn surpasse 10 m on trans stors per c p.

Introduction of 64-bit processors

Intel leads the show with Pentium, Celeron and dual

and quad core processors working with up to 3.5GHzspeed.


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General Purpose Processors - Comparison



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Microprocessors can be classified based on their

purpose, architecture, specifications and applications.

Based on the size of the data that the microprocessor

Classification of Microprocessors


, - , - , - , -

bit and 64-bit microprocessors.

Based on the application of the processors, they are

classified as i) General purpose processors, ii)

Microcontrollers and iii) Special purpose processors.


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General Purpose Processors

General purpose processors are those which are used in

general computer system integration and can be used by

the programmer for any application.


Pentium processors are examples of general purposeprocessors.

Microcontrollers are the microprocessor chips with in

built hardware for the memory and ports.

These chips are can be programmed by the user for any

generic control applications.


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Special Purpose Processors

Special purpose processors are designed specifically to

handle special functions required for an application.

The digital signal processors are examples for the special


to handle signal processing.

The Application Specific Integrated Circuits (ASIC) chips

are also the examples of this category of

microprocessors.


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Classification of microprocessors

Based on the architecture and hardware of the

processors, they are classified asa)RISC processors,


,

c)VLIW processors and

d)Superscalar processors.

Reduced Instruction Set Architecture, is a processor

architecture that supports limited or small number of

machine language instructions.


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RISC processors can execute the programs faster than

CISC processors. CISC Complex Instruction Set Computing architecture

a CISC rocessors have about 70 to few hundred


instructions and are easier to program.b) CISC processors are slower and more expensive thanRISC processors.

c) Very Long Instruction Word (VLIW) processors haveinstruction composed of many machine operationswhich can be executed in parallel.


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This is achieved by many functional units operating in

parallel.

It has large number of registers and instruction level


.

Superscalar processors are using complex hardware toachieve parallelism.

It is possible to have overlapping of execution of

instructions in order to increase the speed of execution.


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Memory Unit An Introduction

Memory unit is the integral part of any microcomputer

system and its primary purpose is to hold program anddata.

The major design goal of memory unit is to allow it to


operate at a speed close to that of the processor.

The cost factor inhibits the design of entire memory unitwith single technology that guarantees high speed.

In order to seek a trade-off between the cost and

operating speed, a memory system is usually designedwith different technologies such as solid state, magneticand optical.


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A microcomputer memory can be logically

divided into four groupsa) Processor memory/ register


b) Cache memory

c) Primary or Main Memory

d) Secondary memory


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Processor Memory refers to a set of CPU registers.

Processor registers are the first set of storage deviceavailable for the programmers to store any data.

But the are enerall few in number u to about


few tens to hundreds. As these registers are available within the processor,

they are the fastest memory registers.

The main disadvantage is the cost involved whichforces to restrict the number to very few registers offew bytes.


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Cache memory is the fastest external memory to the

processor and they are placed close to the processor.

The instructions to be executed are placed in cache


.

kilobytes in size. These are semiconductor RAMs and are volatile.

The processor will fetch the next instruction from the

cache memory and if the instruction is not in cache, itwill refer to primary memory.


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Primary memory is the storage area from which all the

programs are executed.

All the programs and corresponding data must be within


.

The size of primary memory is much larger compared toprocessor memory and cache memory but its operating

speed is slower than them.

The primary memory in a system varies from fewKilobytes to about 1 Megabyte.


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Secondary memory refers to the storage medium for

huge files such as program source codes, compilers,operating systems etc.


the microprocessor in a computer system. They comprises of slow devices such as magnetic tapes

and optical disks.

Sometimes they are referred to as auxiliary or backupstore.


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Stored information in a magnetic tape or magnetic disk

is not lost when the power is turned off.

Therefore these storage devices are called nonvolatile


.


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Primary Memory - Classification

Primary memory normally includes ROM (Read Only

Memory) and RAM (Random Access Memory).

Microprocessor based systems have at least one RAM


.

Information stored in semiconductor random accessmemories RAM will be lost if the power is turned off.

This property is known as volatility and hence, RAMs

are usually called volatile memories.

ROM is a nonvolatile memory.


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Primary Memory - Classification



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Primary Memory - Classification As the name implies, a ROM permits only a read access.

There are many kinds of this category. Mask Programmable ROMS are custom made for thecustomer and their contents are programmed by the


.

Since they are mass produced, they are inexpensive. Thecustomer can not erase or program it afterwards.

Programmable ROMs are the devices which can be

programmed by the user at the users place or field. The main disadvantage of PROMs is that they cannot beerased and reprogrammed


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EPROM Erasable and Programmable ROMs (EPROMs) allow the

erasure and reprogramming of the content by the user. In an EPROM, programs are entered using electrical


rays.


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EPROM Electrically Erasable PROMs (EEPROMs) or Electrically

Alterable ROMs (EAROMs) allow the users to erase itscontents by electrical means and also reprogramming by

electrical si nals.


EEPROMs are different from RAMs in the electricalsignal required to erase and program. EEPROMs require

a higher voltage for erasing and programming other

than the normal 5V supply.


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Static RAM In a semiconductor memory constructed using bipolar

transistors, the information is stored in the form ofvoltage levels in flip-flops.

Such memories are called static RAMs because stored


n ormat on rema ns constant or some per o o t me.

Static RAM maintains information in active circuits,power is required even when the chip is inactive orstandby mode.

Hence, static RAMs require large power supplies. Also each static RAM cell is about four times larger in

area than an equivalent dynamic cell.


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Dynamic RAM Semiconductor memories designed using MOS

transistors, the information is held in the form ofelectrical charges in capacitors.

the stored char e has the tendenc of et leaked awa .


These memories are referred to as dynamic RAMs. In order to prevent any information loss, dynamic RAMS

have to be refreshed at regular intervals. Refreshing

means boosting the signal level and writing it back. This activity is performed using a hardware unit called

refresh logic.


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Differences



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Input and Output Devices The input/output or I/O section allows the computer to

take in data from the outside world or send data to theoutside world.

Peripherals such as keyboards, video display terminals,


printers, and modems are connected to the I/O section.

These allow the user and the computer to communicate

with each other.

The actual physical devices used to interface thecomputer buses to external systems are often called

ports.


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Function of I/O Ports An input port allows data from a keyboard, an A/D

converter, 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 peripheral devices, such as a video display terminal, aprinter, or a D/A converter.


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Function of I/O Ports Simplest type of input or output port is just a set of

parallel D flip-flops. If they are being used as an input port, the D inputs are

connected to the external device and the out uts are


connected to the data bus which can take the data tothe CPU.

Data will then be transferred to the data bus when they

are enabled by a control signal from the CPU.


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Function of I/O Ports In a system, where they are being used as an output

port, the D inputs of the latches are connected to thedata bus, and the Q outputs are connected to some

external device.


Data sent out on the data bus by the CPU will betransferred to the external device when the latches areenabled by a control signal from the CPU.


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Input Devices Input devices include typewriter-like keyboards; hand-held

devices such as the mouse, trackball, joystick, and specialpen with pressure-sensitive pad; and microphones.

The simplest input device is a switch.


Input devices can also be sensors that provide informationabout their environment temperature, pressure, and so

forth to a computer.

Another direct-entry mechanism is the optical laser

scanner (e.g., scanners used with point-of-sale terminals

in retail stores) that can read bar-coded data or optical

character fonts.


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Output Devices An output is any device through which the user can receive

the results from the computer. The output can be any display which can be changing fast

or hard co ies rint out. Some other forms of out ut are


sounds and alarms. The simplest output devices used in almost all

microprocessor based systems or computer systems are

the LEDs or the seven segment LED displays and LCD

displays.


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Output Devices The advanced video display terminals (either cathode-ray

tubes or liquid crystal displays), ink-jet and laser printers,are the common output devices nowadays.

Some out ut devices can be used to directl control


machineries. Some devices, such as display terminals with touch screen,

may provide both input and output.

Modems and other network interface cards can also becalled as output devices as they enable the transmission

and reception of data between computers.


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Technological Improvements Technology improvements are taking place fast in the

microprocessor, microcomputer and personal computersystems.

The technical and research im rovements in the field of


microprocessor technology is listed below.Increase in data bus / address bus width. The

processing capability of the microprocessor can be

drastically improved by increasing data size


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Technological Improvements Reduction in size and increase in capability

a) The trend in microprocessor technology is to includelarge amount of peripherals such as memory and I/O

ports within a single chip.


b) Microcontrollers are manufactured by allsemiconductor manufacturers in this aspect.

c) Development in the processing of large scale

integration has lead to small chips of microprocessors

with large built in peripherals.

d) We have now processors with large amount of flash

memory available in the market.


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Technological Improvements Development of external peripherals

a) The use of computers in all the fields have resulted inthe development of many fast and advanced peripheral

devices to be interfaced with the micro rocessor.


b) For example, applications of microprocessors inmedical field has resulted in many handheld electronic

devices with the specialized input sensors and output

printers etc.

c) The faster peripherals can increase the speed of

processor execution and a good user interface.


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Technological Improvements Increase in memory size and speed

a) The developments in the Integrated circuittechnology have lead to developments in the reduction

of the memor size and the increase in memor s eed.


b) This reduces the memory access time of theprocessor and so will result in the higher speed of

execution.

c) Also more amount of memory per unit area ispossible


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Technological Improvements The microprocessors are largely used in handheld

devices operated from the battery source. This has resulted in the research towards reduction of

ower consum tion in the micro rocessor chi s.


As power consumption is reduced, the devices can workfor more time with one full charge of batteries.

There are many devices operating at 3.3V are even

lower and have low power consumption.


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Summary Microprocessor is an electronic circuit that functions as

the central processing unit (CPU) of a computer,providing computational control.

The micro rocessor is the controllin element in a


computer system.

The microprocessor performs data transfers, does

simple arithmetic and logic operations, and makes

simple decisions


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Summary The basic operation of the microprocessor is to fetch

instructions stored in the memory and execute them oney one in sequence.

Micro rocessors are used in almost all advanced


electronic systems Microcontrollers are advanced forms of microprocessors

with memory and ports present within the chip


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Summary A microcomputer system is made y interfacing memory

and I/O devices to a microprocessor Microprocessor evolution is classified into five


The processors that are currently in use belong to thefifth generation.

micro intro lecture 2

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