chap6 micro processors

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Chapter-5Introduction to Microprocessors



Microprocessor:

• A single chip that contains a whole CPU – Has the ability to fetch and execute instructions

stored in memory

–

Has the ability to access external memory,external I/O and other peripherals

• Examples:

– Intel P4 or AMD Athlon in desktops/notebooks

– ARM processor in Apple iPod



Microprocessor:

• The key element of all computers, providing themathematical and decision making ability

• Current state-of-the-art uPs (Pentium, Athlon, SPARC,

PowerPC) contain complex circuits consisting of tensof millions of transistors

• They operate at ultra-fast speeds – doing over a

billion operations very second

• Made up from a semiconductor, Silicon



Microprocessor Generations:

• First generation: 1971-78

– Behind the power curve(16-bit, <50k transistors)

• Second Generation: 1979-85 – Becoming “real” computers

(32-bit , >50k transistors)• Third Generation: 1985-89

– Challenging the “establishment”(Reduced Instruction Set Computer/RISC,>100k transistors)

• Fourth Generation: 1990- – Architectural and performance leadership

(64-bit, > 1M transistors,Intel/AMD translate into RISC internally)



1st Generation (16-bit) Intel 8086:

• Introduced in 1978

– Performance < 0.5 MIPS

• New 16-bit architecture

– “Assembly language”

compatible with 8080

–

29,000 transistors – Includes memory

protection, support for

Floating Point coprocessor

• In 1981, IBM introduces PC

– Based on 8088--8-bit busversion of 8086



2nd Generation (32-bit) Motorola 68000:

• Major architectural step in

microprocessors: – First 32-bit architecture

• initial 16-bit implementation

– First flat 32-bit address

• Support for paging

– General-purpose registerarchitecture

• Loosely based on PDP-11minicomputer

• First implementation in 1979

– 68,000 transistors

–

< 1 MIPS (Million InstructionsPer Second)

• Used in

– Apple Mac

– Sun , Silicon Graphics, & Apolloworkstations



3rd Generation: MIPS R2000:

• Several firsts:

– First (commercial) RISC

microprocessor

– First microprocessor to

provide integrated support for

instruction & data cache

– First pipelined microprocessor

(sustains 1 instruction/clock)

• Implemented in 1985

– 125,000 transistors

–

5-8 MIPS (Million Instructionsper Second)



4th Generation (64 bit) MIPS R4000:

•First 64-bit architecture

• Integrated caches

– On-chip

– Support for off-chip,

secondary cache

• Integrated floating point

• Implemented in 1991:

– Deep pipeline

– 1.4M transistors

–Initially 100MHz

– > 50 MIPS

• Intel translates 80x86/ Pentium X

instructions into RISC internally



History of Microprocessors:

• 1974 – the first real useful 8-bit microprocessor is

released by Intel – the 8080 – Motorola introduces the 6800 series

– Zilog has the Z80

• 1975 – GM and Ford begin to put microcontrollers incars

– Many cars today have over 100 microcontrollers

– TI gets into the microprocessor business withcalculators and digital watches

• 1977 – Apple II is released using MOS 6502 (similar to

motorola 6800). Apple II dominated from 1977 to 1983• 1978 – Intel introduces the first 16-bit processor, the

8086

– Motorola follows with the 68000 which is ultimatelyused in the first Apple Macintosh



History of Microprocessors:

• 1981 – IBM enters the PC making market and usesthe Intel 8088 – proliferation of the home computer

• 1982-1985 – Intel introduces the 32-bit 80286 and

80386• 1989 – 80486 is being used in PC’s, able to run

Microsoft Windows

• 1992 – Apple, IBM and Motorola begin to make

PowerMac and PowerPC’s using Motorola chips• 1993 – Pentium chip is released



Those components are … • Devices

– Transistors

– Diodes

– Resistors

– Capacitors – Wires

•

And are made of the following materials – Silicon - semiconductor

– Copper - conductor

–

Silicon Dioxide - insulator



What is a Microprocessor System:



uP Building Blocks



Registers

Registers

Microprocessor

Instruction

Cache

Arithmetic

& Logic

Unit

Control

UnitBus

Interface

Unit

Data

Cache

Instruction

Decoder

I/O

RAM

Memory

Bus

System

Bus

FloatingPoint

Unit



Bus Interface Unit:

• Receives instructions & data from main memory

• Instructions are then sent to the instruction cache,

data to the data cache

• Also receives the processed data and sends it to themain memory



Computer Buses:

•

Address bus: carries the address of a uniquememory or input/output (I/O) device

• Data bus: carries data stored in memory (or an I/O

device) to the CPU or from the CPU to the memory(or I/O device)

•Control bus: is a collection of control signals thatcoordinate and synchronize the whole system



• The MPU communicates with Memory and

I/O using the System Bus: – Address bus

• Unidirectional

•

Memory and I/O Addresses – Data bus

• Bidirectional

• Transfers Binary Data and Instructions

– Control bus

• Read and Write timing signals



Instruction Decoder:

• This unit receives the programming instructions and

decodes them into a form that is understandable by

the processing units, i.e. the ALU or FPU

• Then, it passes on the decoded instruction to the

ALU or FPU



Arithmetic & Logic Unit (ALU):

• Also known as the “Integer Unit”

• It performs whole-number math calculations(subtract, multiply, divide, etc) comparisons (isgreater than, is smaller than, etc.) and logicaloperations (NOT, OR, AND, etc)

•

The new breed of popular uPs have not one but twoalmost identical ALU’s that can do calculationssimultaneously, doubling the capability



Floating-Point Unit (FPU):

• Also known as the “Numeric Unit”

• It performs calculations that involve numbers represented inthe scientific notation (also known as floating-pointnumbers).

• This notation can represent extremely small and extremelylarge numbers in a compact form

• Floating-point calculations are required for doing graphics,

engineering and scientific work

• The ALU can do these calculations as well, but will do themvery slowly



Registers:

• Both ALU & FPU have a very small amount of super-

fast private memory placed right next to them for

their exclusive use. These are called registers

• The ALU & FPU store intermediate and final results

from their calculations in these registers

• Processed data goes back to the data cache and

then to main memory from these registers



Control Unit:

• The brain of the uP

• Manages the whole uP

• Tasks include fetching instructions & data,

storing data, managing input/output

devices



Microcontroller:

• Microcontroller is a single chip micro computermade through VLSI fabrication.

• A microcontroller also called an embedded

controller because the microcontroller and its

support circuits are often built into, or embedded

in, the devices they control.

• A microcontroller is available in different word

lengths.(4bit,8bit,16bit,32bit,64bit and 128 bit)



• Any device that measures, stores, controls, calculates,or displays information must have a microcontrollerchip inside.

• The largest single use for microcontrollers is inautomobile industry (microcontrollers widely used forcontrolling engines and power controls inautomobiles).

•

You can also find microcontrollers inside keyboards,mouse, modems, printers, and other peripherals.

• In test equipments, microcontrollers make it easy toadd features such as the ability to storemeasurements, to create and store user routines, and

to display messages and waveforms.• Consumer products that use microcontrollers include

digital camcorders, optical players, LCD/LED displayunits, etc.



Microcontroller structure:



CPU: • CPU is the brain of a microcontroller .

•CPU is responsible for fetching the instruction, decodesit, then finally executed. CPU connects every part of amicrocontroller into a single system.

• The primary function of CPU is fetching and decodinginstructions.

• Instruction fetched from program memory must bedecoded by the CPU.

Memory:

• The function of memory in a microcontroller is same as

microprocessor. It is used to store data and program.• A microcontroller usually has a certain amount of RAM

and ROM (EEPROM, EPROM, etc) or flash memories forstoring program source codes.



Parallel input/output ports: • Parallel input/output ports are mainly used to

drive/interface various devices such as LCD’S, LED’S,

printers, memories, etc to a microcontroller.Serial ports: • Serial ports provide various serial interfaces between

microcontroller and other peripherals like parallel ports.

Timers/counters: • This is the one of the useful function of a microcontroller.

• A microcontroller may have more than one timer andcounters.

• The timers and counters provide all timing and counting

functions inside the microcontroller.• The major operations of this section are perform clock

functions, modulations, pulse generations, frequencymeasuring, making oscillations, etc. This also can be usedfor counting external pulses.



Analog to Digital Converter (ADC):

• ADC converters are used for converting the analog

signal to digital form.• The input signal in this converter should be in analog

form (e.g. sensor output) and the output from thisunit is in digital form.

• The digital output can be use for various digitalapplications (e.g. measurement devices).

Digital to Analog Converter (DAC): • DAC perform reversal operation of ADC conversion.

• DAC convert the digital signal into analog format. Itusually used for controlling analog devices like DCmotors, various drives, etc.



Interrupt control: • The interrupt control used for providing interrupt

(delay) for a working program.• The interrupt may be external (activated by using

interrupt pin) or internal (by using interruptinstruction during programming).

Special functioning block:

• Some microcontrollers used only for some specialapplications (e.g. space systems and robotics)these controllers containing additional ports toperform such special operations.

• This considered as special functioning block.



Advantages of Microcontrollers:

• a) Microcontrollers act as a microcomputer

without any digital parts.• b) As the higher integration inside microcontroller

reduce cost and size of the system.

•

c) Usage of microcontroller is simple, easy fortroubleshoot and system maintaining.

• d) Most of the pins are programmable by the user

for performing different functions.

• e) Easily interface additional RAM, ROM,I/O

ports.

• f) Low time required for performing operations.



Applications:

• Microcontrollers are widely used in modern

electronics equipments.

• Some basic applications of microcontroller is

given below.

a) Used in biomedical instruments.

b) Widely used in communication systems.

c) Used as peripheral controller in PC.d) Used in robotics.

e) Used in automobile fields.



Microprocessor Vs Microcontroller



MICROCONTROLLER VERSUS

MICROPROCESSOR: MICROPROCESSOR MICROCONTROLLER

It contains ALU, control unit, differentregisters and interrupt circuit.

It contains microprocessor memory(ROM &RAM), I/O interfacing circuit, serial 1/O, timer

etc.

It has many instructions to move data

between memory and CPU.

It has one or two instructions to move data

between memory and CPU.

It has one or two bit handling instructions. It has many bit handling instructions.

Access times for memory and I/O devices are

more.

Less access time for built in memory and I/O

devices.

The system requires more hardware Less hardware reducing PCB size andincreasing the reliability

It is more flexible in design point of view Less flexible

Has single memory map for data and code Has a separate memory map for data and

code

Less number of pins are malfunctioned More pins are malfunctioned



Microprocessors Microcontrollers

1 It is only a general purpose computer CPU It is a micro computer itself

2 Memory, I/O ports, timers, interrupts are notavailable inside the chip

All are integrated inside themicrocontroller chip

3 This must have many additional digital

components to perform its operation

Can function as a micro computer

without any additional components.

4 Systems become bulkier and expensive. Make the system simple, economic andcompact

5 Not capable for handling Boolean functions Handling Boolean functions

6 Higher accessing time required Low accessing time

7 Very few pins are programmable Most of the pins are programmable

8 Very few number of bit handling instructions Many bit handling instructions



Instruction Set:

• The set of machine instructions that a uP recognizes

and can execute – the only language uP knows

• An instruction set includes low-level, a single step-at-a-time instructions, such as add, subtract, multiply,

and divide

• Each uP family has its unique instruction set

• Bigger instruction-sets mean more complex chips(higher costs, reduced efficiency), but shorterprograms



• An instruction generally specifies:

a. The task to be carried out.

b. The addresses in the memory where the operands

are available.

c. The address in the memory where result has to be

stored.

d. The address in the memory where next instruction

an be found.



Programming Software:

• Machine Language: – Binary Instructions

– Difficult to decipher and write

•Error-prone

– All programs converted into machine language

for execution

Instruction Hex Mnemonic Description Processor10000000 80 ADD B Add reg B to Acc Intel 8085

00101000 28 ADD A, R0 Add Reg R0 to Acc Intel 8051

00011011 1B ABA Add Acc A and B Motorola 6811



•

It is difficult to write program in sets of 0 and 1.

• Manufacturers have devised English-like language

words to represent binary instruction.

• Programmers can write programs called assembly

language programs.



• Assembly Language:

– Machine instructions represented in

mnemonics

– One-to-one correspondence

– Efficient execution and use of memory

– Machine-specific



• High-Level Languages:

– BASIC, C, and C++

–

Written in statements of spoken languages – Machine independent

– Easy to write and troubleshoot

– Larger memory and less efficient execution



Complex Instruction set

computer (CISC):

• In the 1970’s & 80’s memory was both slow andexpensive.

• High cost and poor performance facilitated the

need for compact and efficient code.Code written in a high level language took muchlonger to translate into assembler, which lead tobloated code and slower program execution.

• bigger program->more storage->more money• Hence needed to reduce the number of instructions

per program



Complex Instruction set computer

(CISC):

• Number of instructions are reduced by havingmultiple operations within a single instruction

• Multiple operations lead to many different kinds of

instructions that access memory

• In turn making instruction length variable and fetch-

decode execute time unpredictable – making it

more complex

• The CISC philosophy was to shift some of theprogramming burden to the hardware level.

• Thus hardware handles the complexity



Complex Instruction set computer

(CISC):

Features:

Large No. of instructions.

Single instruction will perform a complex operation.

Number of instructions per program is minimised.

Execution time for each instruction is different.

Execution time for an instruction may take several clock

cycles.

Efficient use of memory space.

Works faster for complex instructions but may be slow forsimple tasks.

Emphasis on complex hardware to store a large

instruction set



Most common examples of CISC

Intel 8080,80286,80386,Pentium.

Motorola 68000

Zilog Z80



Pros and Cons of CISC:

• Pro:

– Complex instructions operate

directly on main memory.

– Programmer is no longer

required to do a direct call to

LOAD and STORE operations

as they are now handled by

hardware.

– Compiler has less work to

translate statements in a

high level language to

assembly language.

• Con:

– Microcode became more

difficult to test and debug as

systems became more complex

requiring numerous patches to

fix bugs.

– Programmers weren’t using the

more complex instructions sets

in favor of smaller instructions

that accomplished the same

result.

– The use of memory operands

caused structural hazards

preventing concurrent

execution of instructions.

(pipelining)



• Only 20% of the available instructions were

being used.

• Transistors currently allocated to these

complex instruction sets could be better

utilized elsewhere to gain performance.

Observations leading to RISC

methodology:



Reduced Instruction Set Computer

(RISC): •

Original idea to reduce the ISA( Instruction Set Architecture)• Provide minimal set of instructions that could carry out all

essential operations

• Instruction complexity is reduced by:

•1. Having few simple instructions that are the same length

• 2. Allowed memory access only with explicit load and store

instructions

• Hence each instruction performs less work but instruction

execution time among different instructions is consistent• The complexity that is removed from ISA is moved into the

domain of the assembly programmer/compiler



Reduced Instruction Set Computer



(RISC):

One cycle execution time.

Pipelining: Different parts of an instruction are executedsimultaneously.

Reduced complexity in hardware.

Less hardware space for transistors in the silicon for eachinstruction.

Large register set: Variables and intermediate results are stored in the

registers.

Complex operations are performed as a series of simple RISCinstructions.

Instructions are of fixed length and format.

Emphasis on software for each task.

Program consists of large code size.

Only load and store instructions refer to the memory and

may take more than one clock cycle.



• RISC uses only register to register operations

• Only LOAD and STORE operations have access to

memory

• Separation of LOAD and STORE instructions allowsthe compiler to shift these operations around for

maximum efficiency during execution.

• Simple instructions require fewer transistors which

make the chips easier to design and cheaper to

produce

Advantages of RISC:



• The difference between CISC and RISC becomesevident through the basic computer performance

equation:

• CPU TIME = time/program = [ (instructions/program) x (cycles/instruction) x (time/cycle) ]

• RISC systems shorten execution time by reducing theclock cycles per instruction (i.e. simple instructionstake less time to interpret)

• CISC systems shorten execution time by reducing thenumber of instructions per program



RISC:

To multiply two numbers, firstload each operand from a

location in main memory

(locations 1:1 through 6:4) into

one of the six registers (A, B,

C, D, E, or F). Once loaded,

they can be multiplied by the

execution unit (or ALU).

1. LOAD [A, 2:3]2. LOAD [B, 5:2]

3. MULT [A, B]

4. STORE [2:3, A]



CISC:

• CISC ‘rolls up’ thisinstruction set into onecompact instruction tobe handled by the

decoder.• MULT [2:3, 5:2]

• Microcode enginewithin the CPU decodesthe complex instructionsand executes microcodeprograms to carry outthe task



CISC versus RISC



CISC versus RISCCISC RISC

Emphasis on hardware Emphasis on software

Includes multi-clock

complex instructions

Single-clock,

reduced instruction only

Variable length instructions Fixed length instructions

Memory-to-memory:

"LOAD" and "STORE"incorporated in instructions

Register to register:

"LOAD" and "STORE"are independent instructions

Small code sizes,

high cycles per second

Low cycles per second,

large code sizes

Transistors used for storing

complex instructions

Spends more transistors

on memory registersMany addressing modes

Few addressing modes

Complexity in microcode Complexity in compiler



Binary & Decimal Numbers:

BINARY

(BASE 2)

numbers



DECIMAL

(BASE 10)

numbers



Decimal (base 10) number system consists of 10

symbols or digits

0 1 2 3 4

5 6 7 8 9



Binary (base 2) number system consists of just

two

Oth l b t



Other popular number systems:

•Octal – base = 8

– 8 symbols (0,1,2,3,4,5,6,7)

• Hexadecimal

– base = 16

–

16 symbols (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F)



Decimal (base 10) numbers are expressed in the

positional notation

4202 = 2x100 + 0x101 + 2x102 + 4x103

The right-most is the least significant digit

The left-most is the most significant digit



Decimal (base 10) numbers are expressed in the positional notation

4202 = 2x100 + 0x101 + 2x102 + 4x103

1’s multiplier

1




4202 = 2x100 + 0x101 + 2x102 + 4x103

10’s multiplier

10




4202 = 2x100 + 0x101 + 2x102 + 4x103

1000’s multiplier

1000



Binary (base 2) numbers are also expressed in the

positional notation

10011 = 1x20 + 1x21

+ 0x22 + 0x23

+ 1x24

The right-most is the least significant digit

The left-most is the most significant digit



Binary (base 2) numbers are also expressed in

the positional notation

10011 = 1x20 + 1x21

+ 0x22 + 0x23

+ 1x24

1’s multiplier

1





10011 = 1x20 + 1x21

+ 0x22 + 0x23

+ 1x24

2’s multiplier

2



Binary (base 2) numbers are also expressed in the

positional notation

10011 = 1x20 + 1x21

+ 0x22 + 0x23

+ 1x24

4’s multiplier

4



Binary (base 2) numbers are also expressed inthe positional notation

10011 = 1x20 + 1x21

+ 0x22 + 0x23

+ 1x24

8’s multiplier

8





10011 = 1x20 + 1x21

+ 0x22 + 0x23

+ 1x24

16’s multiplier

16



Why binary ?Because this system is natural for digital computers

The fundamental building block of a digital computer –

the switch – possesses two natural states, ON & OFF.

It is natural to represent those states in a number system

that has only two symbols, 1 and 0, i.e. the binary

number system



Decimal Binaryconversion



Check



Check

1001011 = 1x20 + 1x21 + 0x22 + 1x23 +

0x24 + 0x25

+ 1x26

= 1 + 2 + 0 + 8 + 0 + 0 + 64

= 75

Convert 100 to Binary



Convert 100 to Binary

1002

50 02

25 02

12 12

6 02

3 02

1 12

0 1

1100100

remainder



Logic Gates



Let x , y , z be Boolean variables. Booleanvariables can only have binary values i.e., they

can have values which are either 0 or 1

For example, if we represent the state of a light

switch with a Boolean variable x , we will assign a

value of 0 to x when the switch is OFF, and 1

when it is ON

A f th f th t t f



A few other names for the states of

these Boolean variables

0 1

Off On

Low High

False True



Boolean Algebra to Logic Gates:



• Logic circuits are built from components called

logic gates.• The logic gates correspond to Boolean operations

+, *, ’

• Binary operations have two inputs, unary has one

OR

+

AND

*

NOT

’



Truth Table for the AND Operation



p

(z true when both x & y true)

x y z = x · y

0 0

0 1

1 0

1 1



AND Gate:

x

y

x*y = z

Logic Gate:

Series Circuit:

x y

x y z

0 0 0

0 1 0

1 0 0

1 1 1

Truth Table:x*y = z

AND Gate Timing Diagram:



• A high output is obtained when both inputs are

high.

• For all other conditions output is low.

• AND is boolean multiplication so that a*b denotes a

AND b.

x

y

xy



OR Gate

Truth Table for the OR Operation




(z true when x or y or both true)

x y z = x + y

0 0

0 1

1 0

1 1





x y z = x + y

0 00

0 1 1

1 01

1 1 1

OR Gate:



XY

Z

Logic Gate:

Parallel Circuit:

X

Y

X Y Z

0 0 0

0 1 1

1 0 1

1 1 1

Truth Table:

X+Y = Z



Truth Table for the NOT Operation



(y true whenever x is false)

x y = x´

0

1





x y = x´

0 1

1 0

NOT Gate:



NOT Gate:

x

Y or x’

Logic Gate:

(also called an inverter)

Single-throw

Double-pole

Switch:

x

x y

0 11 0

Truth Table:Y or x’



NAND and NOR Gates:



• NAND and NOR gates can greatly simplify circuit diagrams. As

we will see, can you use these gates wherever you could useAND, OR, and NOT.

NAND

NOR



NAND Gate

NAND Gate :



NAND Gate (NAND = Not AND) :

• It is a combination of AND gate followed by a NOT Gate

NAND

A B Y=AB

0 0 1

0 1 1

1 0 1

1 1 0

NAND Gate Timing Diagram:



NAND Gate Timing Diagram:

• NAND Gate is an AND Gate with output inverted.

y



NOR Gate

NOR Gate (NOR = Not OR):



• It is a combination of OR gate followed by aNOT Gate

A B Y= AB

0 0 1

0 1 0

1 0 0

1 1 0NOR

NOR Gate Timing Diagram:



NOR Gate Timing Diagram:

• NOR Gate is an OR Gate with output inverted

Y

B

A



XOR Gate

XOR Gate (Exclusive OR Gate):



( )

• It is an OR Gate with a NOT gate applied to one of

its inputs

• It can also be a AND gate with a NOT gate as an

input to it.

XOR

A

B A + B = Y

_

Truth Table for the XOR Operation



(z true when x or y true, but not both)

x y z = x y

0 0

0 1

1 0

1 1





x y z = x y

0 0 0

0 1 1

1 0 1

1 1 0

XOR Gate Timing Diagram:



• When one input is high and other low there will be

an output.• When both the inputs are high/low there will be no

output.

Y

Combining Logic Gates:



g g



122

• Find the output of the following circuit

• Answer: ( x+y )y

x

y x +y

y

( x +y )y

__



• Find the output of the following circuit

• Answer: xy

x

y

x

y

x y x y

_ _ ___

chap6 micro processors

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