introduction of microprocessor

8/7/2019 Introduction of Microprocessor

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Introduction:

A Microprocessor incorporates most or

all of the functions of a computer's central

processing unit (CPU) on a single

integrated circuit (IC, or microchip). The

first microprocessors emerged in the early

1970s and were used for electronic

calculators, using binary-coded decimal

(BCD) arithmetic on 4-bit words. Other

embedded uses of 4- bit and 8-bit

microprocessors, such as terminals,

printers, various kinds of automation etc.,

followed rather quickly. Affordable 8-bit

microprocessors with 16-bit addressing

also led to the first general purpose

microcomputers in the mid-1970s.

Computer processors were for a long

period constructed out of small andmedium-scale ICs containing the

equivalent of a few to a few hundred

transistors. The integration of the whole

CPU onto a single chip therefore greatly

reduced the cost of processing capacity.

From their humble beginnings, continued

increases in microprocessor capacity have

rendered other forms of computers almost

completely obsolete, with one or more

microprocessor as processing element in

everything from the smallest embedded

systems and handheld devices to the

largest mainframes and supercomputers.

Evolution of Microprocessors:

In Early days microprocessor can be

defined as ³a computer processor that is

contained on an integrated chip´. In other

words we can say a microprocessor is a

central processing unit contained on a

large scale integration chip.The

microprocessor has changed the way

computers work by making them faster.

The microprocessor is often called the

brain of the C.P.Uand without the

microprocessor the computer is more or

less useless.

Microprocessor technology is progressing

so rapidly that even experts in the field are

having trouble keeping up with current

advances.

Figure 1: Intel 4004 Microprocessor



What l t the devel ent of

Mi oprocessors?

Microprocessors essentiall evolved from

mechanical relays to integrated circuits. It is impor tant to illustrate here what aspects

of the computing industry that led to the

development of microprocessors.

a) Digital Computer Technology:

Advancement of Digital Computer

Technology by developing new

computers with high processing speed,

smaller in size & less expensive in late

1940¶s.

b) Semiconductors:

Semiconductors had also been growing

steadily since the invention of the

transistor in the late 1940s. In 1960s,

invention of integrated circuit lead us

to develop from just a few transistors

to many complicated tasks, allof them

on the same chi p.

The development of microprocessors can

be attr i buted to when, in the ear ly 1970s,

digital computers and integrated circuits

reached the required levels of capability.

However, the ear ly microprocessor did not

meet all the goals: it was too expensive for

many applications, especially those in the

consumer market, and it could not hold

enough information to perform many of

the tasks being handled by the

minicomputers of that time.

Generations of Microprocessor :

y FIRST-GENERATION:

The microprocessors that were

introduced in 1971 to 1972 were

referred to as the f irst generation

systems. They fetched the instruction,

decoded it, and then executed it.When

the execution was completed then it its

instruction pointer was updated to

fetch next instruction.

Figure 2: INTEL C8080A Mi

The Intel 8080 was an ear ly

microprocessor designed and

manufactured by Intel. The 8-bit

microprocessor was released in Apr il

1974 running at 2 MHz (at up to

500,000 instructions per second), and

is sometimes considered to be the f irst

truly usable microprocessor.The 8080

was implemented using non-saturated

enhancement-load NMOS, demanding

extra voltages.



y SECOND GENERATION:

In 1973, enough transistors were

available on the IC containing: 16-bit

ar ithmetic and pi pelined instruction

processing.

The distinction between the f irst and

second generation devices was

pr imar ilythe use of newer

semiconductor technology to fabr icate

the chi ps. This new technology

resulted in a f ive-fold increase in

instruction, execution, speed,

andhigher chi p densities.

For Example:

Motorola¶s MC68000, microprocessor

introduced in 1979, is an example.

Another example is Intel¶s 8080. This

makes the use of semiconductor

technology.

Figure 3: Motorola MC68000 Mi

roprocessor

y THIRD GENERATION:

It was introduced in 1978 represented

by Intel 8086 having 16 bit processor

like minicomputer like performance. It

consists of single chi p cache.The third

generation came about as IC transistor

counts approached 250,000.This

generation ofmicroprocessors was

different from the previous ones in that

all major workstationmanufacturers

began developing their own RISC-

based microprocessor architectures

were introduced.

For Examples:

Intel¶s 8086/80186/80286, Motorola¶s

68000/68010& AMD 486c

Figure 4: Intel 8086 Microprocessor

The 8086 is a 16-bit microprocessor

chi p designed by Intel, which gave r ise

to the x86 Architecture. Intel 8086

microprocessor is also called iAPX86.

The development work on the 8086

design star ted in 1976 and the chi p was

introduced in the market in 1978.

y FOURTH GENERATION:

As the workstation companies

conver ted from commercial

microprocessors to in-house designs,

microprocessors entered their four th

generation with designs surpassing a

million transistors.

This era marked with the beginning of

32 bits microprocessors.



For Example:

Microprocessors such as Intel¶s

80960CA and Motorola¶s 88100 could

issue and retire more than one

instruction per clock cycle.

Figure 5:Intel 80960 Microprocessor

The 80960 (i960CA) was the f irst pure

RISC implementation of the i960

architecture. It featured a newly-

designed superscalar RISC core and

added an unusual addressable on-chi p

cache, but lacked an FPU and MMU,

as it was intended for high-

performance embedded applications.

The i960CA is widely considered to

have been the f irst single-chi p

superscalar RISC implementation. The

C-ser ies only included one ALU, but

could dispatch and execute an

ar ithmetic instruction, a memory

reference, and a branch instruction at

the same time, and sustain two

instructions per cycle under cer tain

circumstances. The i960CA

microarchitecture was designed in

1987±1988 and formally announced on

1989. Later, the i960CF included a

f loating-point unit, but continued to

omit an MMU.

y FIFTH GENERATION:

Microprocessors in their f if th

generation, employed decoupled super

scalar processing, and their design

soon surpassed 10 million transistors.

In this generation, PCs are a low-

margin, high-volume-business

dominated by a single microprocessor.

For Examples:

Intel leads the show here with Pentium,

Celeron and very recently dual and

quad core processors work ing with up

to 3.5GHz speed.



Figure 6: Intel Core i7 Microprocessor

Basic Architecture of Microprocessor :

Figure 7: Basic Architecture of Microprocessor

The block diagram shows the basic

architecture of a microprocessor based

system. In this system, the microprocessor

is the master and all other per i pherals are

slaves. The master controls all the

per i pherals and initiates all operations.

The microprocessor is the functional

center of the microcomputer system.



Its internal construction can be broadly

divided into three sections:

y Control section

y Ar ithmetic and Logic Unit

y Register section

y System Bus

Control Section:

Control section/unit is the par t of the

microcomputer that controls its basic

operations. It is made up of the control

signal generating circuitry (clock) and thecommand (instruction) decoder.

The control section fetches pre-

programmed instructions from memory

(op-code fetch cycle) as needed and

temporar ily stores them in the command

register (also known as Instruction

Register IR).

These instructions are then decoded by the

operation decoder (decode cycle), which

sends control signals to the relevant par ts

of the microcomputer system (via the

system busses) to cause them to carry out

the required operation (execute cycle).

The timing with which these control

signals are generated is determined by the

clock. The number of T-states tells the

time taken for the CPU to execute that

par ticular instruction.

The major types of operations controlled

by the control signals are :-

a) Sending of data from one par t of the

microcomputer to another (read or wr ite

cycle).

b) Inputting and out putting of data to/from

the microcomputer (I/O read or wr ite

cycle).

c) Ar ithmetic and Logic calculations.

d) Halting of computer instructions.

e) Jumping to another instruction dur ing

running (execution) of a program.

Ar ithmetic and Logic Unit:

Ar ithmetic and Logic Unit comes under

the control of control section carr ies out

the actual processing of data, normally

descr i be as data mani pulation. This

consists largely of ar ithmetic operations

(ADDition, SUBtraction, INCrementing,

DECrementingetc) and logical operations

(ANDing, OR ing, XOR ing, NOTingetc).

The ALU carr ies out these operations in

the following manner :

1) Stores data fetched from memory or I/O

in the registers.

2) Fetches this data as needed from the

registers and/or from relevant

accumulators.



3)Send this data either to its ar ithmetic

circuitry or logical circuitry, where

necessary, where the necessary, ar ithmetic

or logical operations are carr ied out.

4) Send results of its ar ithmetic or logical

operation to relevant accumulator, to the

memory, or to the I/O interfaces.

Register Section:

The register section/array consists

completely of circuitry used to temporar ily

store data or program codes until they are

sent to the ALU or to the control section or

to memory. The number of registers are

different for any par ticular CPU, and the

more register a CPU have will result in

easier programming tasks.

System Bus:

The three components of the

microcomputer system is connected by

three busses, also known as System Bus.

These busses is used to transfer

information (data) internally and

externally to the microprocessor.

a) Address Bus

The address bus is 'unidirectional',

over which the microprocessor sends

an address code to the memory or

input/out put.

The size (width) of the address bus is

specif ied by the number of bits it can

handle.

The more bits there are in the address

bus, the more memory locations a

microprocessor can access. A 16 bit

address bus is capable of addressing

65,536 (64K) addresses.

b) Data Bus:

The data bus is 'bi-directional', on

which data or instruction codes are

transferred into the microprocessor or

onwhich the result of an operation or

computation is sent out from the

microprocessor to the memory or

input/out put.

Depending on the par ticular

microprocessor, the data bus can

handle 8 bit or 16 bit data.

c) Control Bus:

The control bus is used by the

microprocessor to send out or receive

timing and control signals in order to

coordinate and regulate its operation

and to communicate with other

devices, i.e. memory or input/out put.

The lines used to control memory and

I/O devices are MEMRQ*, IORQ*,

RD* and WR*. Others are general

Control signals to handle special

external requests (interrupts), special

I/O devices (DMA) and special k ind

of Memory (DRAM).



Performance of Microprocessors :

The number of transistors available has a

huge effect on the performance of

aprocessor. With more transistors, much

more powerful multi pliers capable of

single-cycle speeds become possi ble.

More transistors also allow a technology

called pi pelining. In a pi pelined

architecture, instruction execution

over laps.

For example:

A microprocessor might take 5 clock

cycles to execute each instruction, there

can be 5 instructions in var ious stages of

execution simultaneously, i.e. eachone

instruction completes in every clock cycle.

Many modern processors have multi ple

instruction decoders, each with its own

pi peline. This allows multi ple instruction

streams, which means more than one

instruction can complete dur ing each clock

cycle. This technique can be quite complex

to implement, so it takes lots of transistors.

The trend in processor design has been

toward full 32-bit ALUs with fast f loating

point processors built in and pi pelined

execution with multi ple instruction

streams. There has also been the addition

of hardware vir tual memory suppor t and

L1 caching on the processor chi p. All of

these trends push up the transistor count,

leading to the multi-million transistor

powerhouses available today.

Three basic character istics stand out:

y Instruction Set: The set of instructions

that the microprocessor can execute.

y Bandwidth: The number of bits

processed in a single instruction.

y Clock Speed: Given in megaher tz

(MHz), the clock speed determines

howmany instructions per second the

processor can execute.

In addition to bandwidth and clock speed,microprocessors are classif ied as being

either RISC (reduced instruction set

computer) or CISC (complex instruction

set computer).

Break through in Microprocessor :

y In ear ly 1940¶s the switching unit were

used as a mechanical relays that are

capable of performing calculations.

y In 1950¶s vacuum tubes were used.The

Atanasoff berry computer was mak ing

use of vacuum tubes a s their switching

device as they can perform calculations

much more faster and in eff icient way

than relay machines.

y Then there comes transistor in

1960¶sthat br ing revolution in the

whole scenar io. It changed the

computer from a giant electronic brain

to a simple commodity like a TV.This



led to the development of the

Minicomputers.

y Then there comes a concept called

³integrated circuit . Intergraded chi ps

are tiny silicon chi ps and are used in

aerospace and for military purposes.

But at that time only big companies

were able to afford this.

y Later on more sophisticated chi p was

introduced and was termed as

³Microprocessor¶.The Microprocessor

is the extension of Ar ithmetic and

Logical unit that is able to extract data

from the memory and interpret it as an

instruction.The term was f irstly

introduced by the Intel in 1972.

y In 1980¶s full scale microprocessor

were developed that consists of 32 bit

address system and has operating

frequency is from 25 to 50 Mhz.

Microprocessors Today:

Technology has been changing at a rapid

pace. Everyday a new product ismade to

make life a little easier. The computer

plays a major role in the lives of

most people. It allows a person to do

practically anything. The Internet enables

the user togain more knowledge at a much

faster pace compared to researching

throughbooks. The por tion of the computer

that allows it to do more work than a

simplecomputer is the Microprocessor.

Microprocessor has brought electronics

into a new era and causedcomponent

manufacturers and end-users to rethink the

role of the computer. Whatwas once a

giant machine attended by specialists in a

room of its own is now a tinydevice

conveniently transparent to users of

automobile, games, instruments,

off iceequi pment, and a large array of other

products.

From their humble beginnings 25 years

ago, microprocessors haveproliferated into

an astounding range of chi ps, power ing

devices ranging fromtelephones to

supercomputers.

Today, microprocessors forpersonal

computers get widespread attention and

have enabled Intel to becomethe wor ld's

largest semiconductor maker. In addition,

embedded microprocessorsare at the hear t

of a diverse range of devices that have

become staples of aff luentconsumers

wor ldwide.

The impact of the microprocessor,

however, goes far deeper than new

andimproved products. It is alter ing the

structure of our society by changing howwegather and use information, how we

communicate with one another, and how

andwhere we work. Computer users want

fast memory in their PCs, but most do

notwant to pay a premium for it.



Bi bliography:

Books Referred:

y Fundamentals of Microprocessors and

Microcomputers by B. Ram

y Microprocessor and Assembly Language

Programming by U. S Shah

Internet Sites:

y www.google.com

y www.ask.com

y www.wik i pedia.com

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