Microprocessors evolution introduction to microprocessor

Microprocessors evolution introduction to microprocessor

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Evolution & Introduction
to Microprocessor
EIntroduction
EBasic terms
ETypes of Microprocessor
EMicroprocessor based system
EOrigin of microprocessor
EClassification of Microprocessor
EMemory unit
EInput & Output devices
EFunctions of I/O ports
ETechnology improvements adapted to microprocessor & Computer
Contents:

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Introduction
EMicroprocessor is an electronic chip that functions as the central
processing unit (CPU) of a computer
EIn other words, we can call microprocessor as the heart of any
computer system.
ESome may call the microprocessors as the brain of the computers.
EThe microprocessor based systems with limited resources are
called as microcomputers.
ENow-a-days microprocessors are found in almost all electronic
machines and appliances in its different form.
ESome common devices using microprocessors are computer
printers, automobiles, washing machines, microwave ovens,
mobile phones, fax machines, Xerox machines and advanced
instruments like radar, satellites, flights etc.,
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EAny middle class house-hold will have about a dozens
microprocessor in different forms inside various appliances.
EThe recent developments in electronic industry and the large
scale integration of devices has led to rapid cost reductionand
more and more application of microprocessors and its derivatives.
EAlmost all microprocessors use the basic concept of “stored
program execution”.
EBy this concept, programs or the instructions to be executedby
the microprocessor are stored sequentially in memory locations.
EThe microprocessor or the processor in general will fetch the
instructions one after the other and execute them it in its
arithmetic and logic unit.

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EA microprocessor can be programmed to do any task that can be
written and programmed by the user.
ESo, in order to work with the microprocessor, it is necessaryfor
the user to know about the internal resources and features ofthe
microprocessor.
EThe programmers must also understand the instructions thata
microprocessor can support.
EEvery microprocessor will have its own associated set of
instructions that it supports and this list is given by all the
microprocessor manufacturers
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EThe instruction set for microprocessors is given in two forms
a) One in mnemonic which is comparatively easy to understand
b) The other in binary machine code which the microprocessorreally
works upon and difficult to understand by us.
EPrograms are written using mnemonics called the assembly level
language and then they are converted into binary machine level
language.
EThis conversion can be done manually or using an applicationcalled
assembler.
EIn general, the programs are written by the user for a microprocessor to
work with real world data.
EThese data are available in many forms and are from many sources.
ETo give this data to the microprocessor, the microprocessorbased
systems need some input interfacing circuits and some electronic
processing circuits.
EThese circuits include data converters and ports
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EAfter processing the real world data, the output from the
microprocessor must be taken out to give to final end effect
instrument or circuits.
EThis again needs interfacing circuits and ports.
ESo, 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.
EAll circuits put together along with microprocessor are called as
microcomputer system.
EThe physical components of the microcomputer system are in
general called as hardware.
EThe program which makes this hardware useful is called as
software.
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Basic terms
vChip
a) 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 particular function.
b) Simpler processors might consist of a few thousand
transistors etched onto a silicon base just a few
millimeters square.

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vBit
a) A bit means a single binary digit.
b) Also, the bit is the fundamental storage unit of
computer memory. In binary, bit can have only two
values, 0 or 1, whereas a decimal digit can have 10
values, represented by symbols 0 through 9.
vBit Size
The bit size of a microprocessor refers to the number
of bits that can be processed simultaneously by the
basic arithmetic circuits of the microprocessor.
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vWord
A number of bits grouped together for processing is
called as word. In microprocessors, the word in
general refers to the basic data size or bit size that can
processed by the ALU of the processor. 16-bit binary
number is called a word in a 16-bit processor.
vMemory 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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vByte
An 8-bit word is referred to as a byte.
vNibble
A 4-bit word is referred to as a nibble.
vKilobyte
A collection of 1024 bytes is called a kilobyte.
vMegabyte
A collection of 1024 Kbytes is called a megabyte.
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vRAM or R/W memory
ERandom Access Memory or Read/ Write memory is
the type of semiconductor memory in which a
particular memory location can be erased and
written with a new data at any time.
EThese memory units are volatile, which means that
the content of the memory is erased when the power
to the chip is disrupted.
EThe access of the individual memory location can be
done randomly. In microprocessors, the RAM is used
to store data.
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vDRAM
a) Dynamic Random Access Memory is a semiconductor
memory in which the stored contents need to be
refreshed repeatedly at about thousands of times per
second.
b) Without refreshing, the stored data will be lost.
c) These memory chips are preferred in a computer system
because it is economical although slower.
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vSRAM
EStatic Random Access Memory chips keep the data
stored in it as long as power is available. There is no
need for refreshing. In terms of speed, SRAM is faster.
vROM
ERead Only Memory are memory devices whose
contents are retained even after removing the power
supply.
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vArithmetic and Logic Unit (ALU)
a) ALU is a digital circuit present in the microprocessor
to do performs arithmetic and logic operations on
digital data.
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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vMicrocontroller
Microcontroller is a chip that includes
microprocessor, memory and I/O signal ports.
Microcontrollers can be called as single chip
microcomputers.
vMicrocomputer
The system formed by interfacing microprocessor
with memory, and I/O devices to work with the
required program is called microcomputer.
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vBus
The bus in a microprocessor system refers to a group of
wires or signals having a common functionality
vSystem Bus
The System bus is a group of signals used for
communication between the microprocessor and
peripherals.
vFirmware
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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vInput device
The devices that are used for giving data to the
microcomputer system are called as input devices.
Usually keyboard and mouse are the input devices
through which data and instructions are given to
computer.
vOutput device
The devices that are used for getting data out from the
microprocessor or microcomputer system are called
as output devices. A display screen, printer and
displays are the common output devices.
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vClock
EThe circuit in the computer that generates the
sequence of evenly spaced pulses to synchronize the
activities of the processor and its peripherals.
EThe clock speed determines the speed of the operation
of the computer.
EThe computer with a high frequency clock works
faster. Normally the clock frequency is in the range of
Mega Hertz, MHz or Giga Hertz, GHz.
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TypesofProcessors
Two types of processors are manufactured
a) The microprocessor
b) The microcontroller
EThe general purpose microprocessors give the computers
all the necessary computing power.
EThese microprocessors need additional circuitry elements
such as memory devices, I/O ports to connect the input
and output devices.
EAll microprocessor based systems need two types of
memories – RAM and ROM.

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Microcontrollers
IThe microcontrollers are the microprocessors designed especially for control
applications.
IMicrocontrollers contain memory units and I/O ports insidea chip in addition
to the CPU part.
IMicrocontrollers are otherwise called as embedded controllers are generally
used to control and operate smart machines.
ISome of the machines using microcontrollers are microwave ovens, washing
machines, sewing machines, automobile ignition systems, computer printers
and fax machines etc.
IOut of 100 processor chips manufactured, 99 are embedded processors and
remaining 1 processor alone goes into general computers.
ILots of semiconductor companies are in the market of microcontrollers and any
application development engineer is flooded with the varie ty of
microcontrollers as the choice.
nThe system consists of CPU, memory and I/O ports
nThe interfacing of the processor with the other parts of the
microcomputer system needs three bus architecture.
nThe three buses are
a) Data bus,
b) Address bus
c) Control bus
Microprocessor based system

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EEach memory location or I/O port is identified by a specific
address similar to the postal address.
EHere, in microprocessor systems, the addresses are all in binary
and in general written in hexadecimal number format.
EThe address is a unique pattern used to identify a location in
memory or I/O port.
EThe address bus consists of many lines that can have the digital
data sent by the processor.
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EAn address bus of 8 bits 2
8
different memory locations.
ESimilarly, the 16-bit address bus can address 2
16
different
addresses. Its address ranges from 0000H to FFFFH.
EThe higher the number of lines of address bus is, the more the
locations the processor is able to manage.
EA control bus is needed for proper data transfer between the
processor and other peripherals.
EThe control bus basically consists of signals like selecting the
proper memory or I/O device from the address; signal to indicate
the direction of data transfer; and the signal to synchronize data
transfer between slow devices.
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Origin of Microprocessor
IThe breakthrough in transistor technology led to the
introduction of minicomputers of the 1960s and the
personal computer revolution of the 1970s.
IIntel was the first MPU producer and has been holding a
large share in the world market of this product.
IMicroprocessors evolution is categorized into five
generations
nfirst, second, third, fourth, and fifth generations.
First Generation (1971-73)
IThe microprocessors that were introduced in 1971 to
1972 were referred to as the first generation systems.
IIntel Corporation introduced 4-bit 4004 at 108 kHz, the
first microprocessor in 1971, co-developed by Busicom, a
Japanese manufacturer of calculators.
IIn 1972, Intel made the 8-bit 8008 and 8080
microprocessors.

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SecondGeneration(1974-78)
IVery large-scale integration (VLSI) lead to chips which
had speeds up to hundreds of millions of switching per
second.
IThe second generation marked the beginning of very
efficient 8 – bit microprocessors.
ISome of the popular processors were Motorola’s 6800
and 6809 and Intel’s 8085, Zilog’s Z80.
IThe distinction between the first and second generation
devices was primarily the use of newer semiconductor
technology to fabricate the chips.
IThey were manufactured using NMOS technology.
Third Generation (1979-80)
IIntroduced in 1978, dominated by Intel’s 8086 and the Zilog
Z8000, which were 16-bit processors with minicomputer-like
performance, have 16-bit arithmetic and pipelined instruction
processing.
ITransistor counts about 250,000.
IMotorola’s MC68020, incorporated an on-chip cache for the first
time and the depth of the pipeline increased to five or more
stages.
IHMOS - speed-power-product of HMOS is four times better than
that of NMOS.
IHMOS can accommodate twice the circuit density compared to
NMOS.

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Fourth Generation (1981-95)
IDesigns with more than a million transistors in a package.
I32 bits microprocessors introduced – Intel 80386 and
Motorola 68020/68030.
IFabricated using low-power version of the HMOS
technology called HCMOS.
Fifth Generation (1995 till date)
IEmployed decoupled super scalar processing.
IChips carry on-chip functionalities and improvements in
the speed of memory and I/O devices
IDesign surpassed 10 million transistors per chip.
IIntroduction of 64-bit processors
IIntel leads the show with Pentium, Celeron and dual and
quad core processors working with up to 3.5GHz speed.

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General Purpose Processors - Comparison
EMicroprocessors can be classified based on their purpose,
architecture, specifications and applications.
EBased on the size of the data that the microprocessor can
handle, they are classified as 4-bit, 8-bit, 16-bit, 32-bitand
64-bit microprocessors.
EBased on the application of the processors, they are
classified as i) General purpose processors,
ii) Microcontrollers and
iii) Special purpose processors.
Classification of Microprocessors

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General Purpose Processors
IGeneral purpose processors are those which are used in
general computer system integration and can be used by the
programmer for any application.
ICommon microprocessor such as Intel 8085 to Intel Pentium
processors are examples of general purpose processors.
IMicrocontrollers are the microprocessor chips with in built
hardware for the memory and ports.
IThese chips are can be programmed by the user for any generic
control applications.
SpecialPurposeProcessors
ISpecial purpose processors are designed specifically to
handle special functions required for an application.
IThe digital signal processors are examples for the special
purpose processors and these have special instructions to
handle signal processing.
IThe Application Specific Integrated Circuits (ASIC) chips
are also the examples of this category of microprocessors.

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Classification of microprocessorsClassification of microprocessorsClassification of microprocessorsClassification of microprocessors
vBased on the architecture and hardware of the processors, they
are classified as
a)RISC processors,
b)CISC processors,
c)VLIW processors and
d)Superscalar processors.
vReduced Instruction Set Architecture’, is a processor architecture
thatsupportslimitedorsmallnumberofmachinelanguage
instructions.
vRISC processors can execute the programs faster than CISC processors.
vCISC – Complex Instruction Set Computing architecture
a) CISC processors have about 70 to few hundred instructionsand are
easier to program.
b) CISC processors are slower and more expensive than RISC
processors.
c) Very Long Instruction Word (VLIW) processors have instruction
composed of many machine operations which can be executed in
parallel.
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vThis is achieved by many functional units operating in
parallel.
vIt has large number of registers and instruction level
parallelism is achieved.
vSuperscalar processors are using complex hardware to
achieve parallelism.
vItispossibletohaveoverlappingofexecutionof
instructionsinordertoincreasethespeedofexecution.
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Memory Unit Memory Unit Memory Unit Memory Unit ––––An IntroductionAn IntroductionAn IntroductionAn Introduction
vMemory unit is the integral part of any microcomputer system
and its primary purpose is to hold program and data.
vThe major design goal of memory unit is to allow it to operate
at a speed close to that of the processor.
vThe cost factor inhibits the design of entire memory unit with
single technology that guarantees high speed.
vIn order to seek a trade-off between the cost and operating
speed,amemorysystemisusuallydesignedwithdifferent
technologiessuchassolidstate,magneticandoptical.

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vA microcomputer memory can be logically
divided into four groups
a) Processor memory/ register
b) Cache memory
c) Primary or Main Memory
d)Secondarymemory
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vProcessor Memory refers to a set of CPU registers. Processor
registers are the first set of storage device available for the
programmers to store any data.
vBut they are generally few in number up to about few tens to
hundreds.
vAs these registers are available within the processor, theyare
the fastest memory registers.
vThe main disadvantage is the cost involved which forces to
restrictthenumbertoveryfewregistersoffewbytes.
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vCache memory is the fastest external memory to the processor
and they are placed close to the processor.
vThe instructions to be executed are placed in cache memory for
access by the processor. These are in few kilobytes in size.
vThese are semiconductor RAMs and are volatile.
vThe processor will fetch the next instruction from the cache
memory and if the instruction is not in cache, it will refer to
primarymemory.
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vPrimary memory is the storage area from which all the programs
are executed.
vAll the programs and corresponding data must be within primary
memory prior to execution.
vThe size of primary memory is much larger compared to
processor memory and cache memory but its operating speed is
slower than them.
vTheprimarymemoryinasystemvariesfromfewKilobytesto
about1Megabyte.
Secondarymemoryreferstothestoragemediumforhugefiles
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vThese are not accessed directly and very frequently by
the microprocessor in a computer system.
vThey comprises of slow devices such as magnetic tapes
and optical disks.
vSometimes they are referred to as auxiliary or backup
store.
vStoredinformationinamagnetictapeormagneticdisk
isnotlostwhenthepoweristurnedoff.
Thereforethesestoragedevicesarecallednonvolatile
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Primary Memory Primary Memory Primary Memory Primary Memory ----ClassificationClassificationClassificationClassification
vPrimary memory normally includes ROM (Read Only
Memory) and RAM (Random Access Memory).
vMicroprocessor based systems have at least one RAM and
ROM chips in it.
vInformation stored in semiconductor random access
memories RAM will be lost if the power is turned off.
vThis property is known as volatility and hence, RAMs are
usually called volatile memories.
vROMisanonvolatilememory.

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vAs the name implies, a ROM permits only a read access.
There are many kinds of this category.
vMask Programmable ROMS are custom made for the
customer and their contents are programmed by the
manufacturer.
vSince they are mass produced, they are inexpensive. The
customer can not erase or program it afterwards.
vProgrammable ROMs are the devices which can be
programmed by the user at the user’s place or field.
vThe main disadvantage of PROMs is that they cannot be
erased and reprogrammed
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EPROMEPROMEPROMEPROM
lErasable and Programmable ROMs (EPROMs) allow the
erasure and reprogramming of the content by the user.
lIn an EPROM, programs are entered using electrical impulses
and the stored information is erased using UV rays.
lElectrically Erasable PROMs (EEPROMs) or Electrically
Alterable ROMs (EAROMs) allow the users to erase its contents
by electrical means and also reprogramming by electrical
signals.
lEEPROMs are different from RAMs in the electrical signal
required to erase and program. EEPROMs require a higher
voltage for erasing and programming other than the normal 5V
supply.
Static RAM
lIn a semiconductor memory constructed using bipolar
transistors, the information is stored in the form of
voltage levels in flip-flops.
lSuch memories are called static RAMs because stored
information remains constant for some period of time.
lStatic RAM maintains information in active circuits,
power is required even when the chip is inactive or
standby mode.
lHence, static RAMs require large power supplies.
lAlsoeachstaticRAMcellisaboutfourtimeslargerin
areathananequivalentdynamiccell.

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Dynamic RAM
lSemiconductor memories designed using MOS
transistors, the information is held in the form of
electrical charges in capacitors.
lThe stored charge has the tendency of get leaked away.
These memories are referred to as dynamic RAMs.
lIn 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.
lThisactivityisperformedusingahardwareunitcalled
“refreshlogic”.
Differences

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Input and Output Devices
lThe input/output or I/O section allows the computer to take
in data from the outside world or send data to the outside
world.
lPeripherals such as keyboards, video display terminals,
printers, and modems are connected to the I/O section.
lThese allow the user and the computer to communicate with
each other.
lTheactualphysicaldevicesusedtointerfacethecomputer
busestoexternalsystemsareoftencalledports.
FunctionofI/OPorts
lAn 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.
lAn output port is used to send data from the computer to
peripheral devices, such as a video display terminal, a printer, or a
D/A converter.
lSimplest type of input or output port is just a set of parallelD flip-
flops.
lIf they are being used as an input port, the D inputs are connected
to the external device, and the Q outputs are connected to thedata
bus which can take the data to the CPU.

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vData will then be transferred to the data bus when they are
enabled by a control signal from the CPU.
vIn a system, where they are being used as an output port,
the D inputs of the latches are connected to the data bus,
and the Q outputs are connected to some external device.
vData sent out on the data bus by the CPU will be
transferred to the external device when the latches are
enabledbyacontrolsignalfromtheCPU.
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Input Devices
vInput devices include typewriter-like keyboards; hand-held devices
such as the mouse, trackball, joystick, and special pen withpressure-
sensitive pad; and microphones.
vThe simplest input device is a switch.
vInput devices can also be sensors that provide information about
their environment temperature, pressure, and so forth to a computer.
vAnother direct-entry mechanism is the optical laser scanner (e.g.,
scanners used with point-of-sale terminals in retail stores) that can
readbar-codeddataoropticalcharacterfonts.

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Output Devices
vAn output is any device through which the user can receive
the results from the computer.
vThe output can be any display which can be changing fast
or hard copies print out. Some other forms of output are
sounds and alarms.
vThe simplest output devices used in almost all
microprocessorbasedsystemsorcomputersystemsare
theLEDsorthesevensegmentLEDdisplaysandLCD.
displays.
vThe advanced video display terminals (either cathode-ray tubes or
liquid crystal displays), ink-jet and laser printers, are the common
output devices nowadays.
vSome output devices can be used to directly control machineries.
vSome devices, such as display terminals with touch screen, may
provide both input and output.
vModems and other network interface cards can also be called as
output devices as they enable the transmission and reception of data
betweencomputers.
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Technological Improvements
vTechnology improvements are taking place fast in the
microprocessor, microcomputer and personal computer
systems.
vThe technical and research improvements in the field of
microprocessor technology is listed below.
EIncrease in data bus / address bus width. The
processing capability of the microprocessor can be
drasticallyimprovedbyincreasingdatasize.
vIncreaseinspeed
EAs the data to be processed by the microprocessors
and computers increased in volume, it became a
necessity to increase the speed of the processor.
EBy high speed processors, the user can get the
results faster even with the large data volumes.
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vReduction in size and increase in capability
EThe trend in microprocessor technology is to include large amount of
peripherals such as memory and I/O ports within a single chip.
EMicrocontrollers are manufactured by all semiconductor
manufacturers in this aspect.
EDevelopment in the processing of large scale integration has lead to
small chips of microprocessors with large built in peripherals.
EWe have now processors with large amount of flash memory available
inthemarket.
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vDevelopment of external peripherals
EThe use of computers in all the fields have resulted in the
development of many fast and advanced peripheral devices
to be interfaced with the microprocessor.
EFor example, applications of microprocessors in medical field
has resulted in many handheld electronic devices with the
specialized input sensors and output printers etc.
E Thefasterperipheralscanincreasethespeedofprocessor
executionandagooduserinterface.

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vIncrease in memory size and speed
EThe developments in the Integrated circuit technology
have lead to developments in the reduction of the
memory size and the increase in memory speed.
EThis reduces the memory access time of the processor
and so will result in the higher speed of execution.
E Alsomoreamountofmemoryperunitareaispossible
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vThe microprocessors are largely used in handheld devices
operated from the battery source.
vThis has resulted in the research towards reduction of
power consumption in the microprocessor chips.
vAs power consumption is reduced, the devices can work
for more time with one full charge of batteries.
vThere are many devices operating at 3.3V are even lower
andhavelowpowerconsumption.
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Summary
vMicroprocessor is an electronic circuit that functions as the
central processing unit (CPU) of a computer, providing
computational control.
vThe microprocessor is the controlling element in a computer
system.
vThe microprocessor performs data transfers, does simple
arithmetic and logic operations, and makes simple decisions.
vThe basic operation of the microprocessor is to fetch instructions
stored in the memory and execute them one y one in sequence.
vMicroprocessors are used in almost all advanced electronicsystems.
vMicrocontrollers are advanced forms of microprocessors with
memory and ports present within the chip.
vA microcomputer system is made y interfacing memory and I/O
devices to a microprocessor
vMicroprocessor evolution is classified into five generations
vThe processors that are currently in use belong to the fifth
generation.
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