MICROPROCESSOR DESIGNING by UPKAR

8/8/2019 MICROPROCESSOR DESIGNING by UPKAR

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SWAMI VIVEKANAND COLLEGE OF ENGINEERING

A literature survey on-

ICROPROCESSOResign using VLSI technologyShyam Kumar [0822ec071099]

Uddhav Shendurnikar [0822ec071112]

Upkar Chauhan [0822ec071113]

Vishakha Nigam [0822ec071118]

Presented by group members-


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It is the heart of a microcomputer system. It is a programmable integrated device that has computing & decision makingcapability similar to CPU.

It comprises of three parts- ALU, control unit, register file.

These are connected with data bus, control bus & internal bus

It communicates &operates in binary nos. 0 & 1 called bits. Each P has a fixed set of instructions in form of binary patterns calledmachine language.

Binary nos are given abbreviated names for interpreting human beings calledmnemonics.

It can be instructed to perform given tasks within its capability. A programmercan select instructions & ask the P to perform various tasks on a given setof data

INTRODUCTION


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A MICROPROCESSOR-BASED system can be represented with four components -

Memory

Input

Output

MicroProcessor


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Components of microprocessor

Ctrl unit

ALURegister

Ctrl

bus

Data bus

Internalbus


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Control UnitThe control unit, as described above, reads the instructions, and generates thenecessary digital signals to operate the other components.

Arithmetic Logic UnitALU is the part of the microprocessor that performs arithmetic operations. ALUs cantypically add, subtract, divide, multiply, and perform logical operations of two numberslike AND, OR, X-OR.

RegistersAnything that can be used to store bits of information, in a way that all the bits of theregister can be written to or read out simultaneously.The registers are the fastest accessible memory locations, and because they are so

fast, there are typically very few of them. In most processors, there are fewer than 32registers.The size of the registers defines the size of the computer.


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Types of Processors

The vast majority of microprocessors are embedded microcontrollers. The secondmost common type of processors are common desktop processors, such as Intel'sPentium or AMD's Athlon.

Microprocessors come in "standard sizes" of 8 bits, 16 bits, 32 bits, and 64 bits.

Some microprocessors come in other "non-standard" sizes such as 4 bits, 12 bits,18 bits &24bits

The number of bits represent how much physical memory can be directly addressedby the CPU & amount of bits that can be read by one read/write operation.

for ex- 8 bit processors can read/write 1 byte at a time and can directly address 256

bytes


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p applications are classified primarily in two categories :

Reprogrammablesystems

Embeddedsystems

qIn reprogrammable systems microprocessor is used for computing & dataprocessing. such as disks , CD-ROMs, printers

qqIn embedded systems, microprocessor is a part of a final product & not

available for reprogramming to end user such as photo copy machine


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General Purpose Versus Specific Use

vMicroprocessors that are capable of performing a wide range of tasks are called

general purpose microprocessors. These are typically the kind of CPUs found indesktop computer systems.

vvDSP (digital signal microprocessor) is a chip that is specifically designed for fast

arithmetic operations, especially addition and multiplication. These chips aredesigned with processing speed in mind.

vv"microcontrollers" are microprocessors with additional hardware integrated into asingle chip. Many microcontrollers have RAM, ROM, A/D and D/A converters,interrupt controllers, timers and even oscillators built into the chip itself.

vvComputer graphics are so complicated that functions to process the visuals of video

and game applications have been offloaded to a special type of processor.


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Types of Use

Signal ProcessingSignal processing is an area that demands high performance from microcontroller

chips to perform complex mathematical tasks. Ex- decoding of digital television andradio signals.

Real Time ApplicationsSome tasks need to be performed so quickly that even the slightest delay orinefficiency can be detrimental. These applications are known as "real time systems.

Ex- anti-lock braking system (ABS) controller in modern automobiles.


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Throughput and Routing

It uses where data is moved from one particular inputto an output, without necessarily requiring any processing.

An example is an internet router, that reads in datapackets and sends them out on a different port.

Sensor monitoring

Many processors, especially small embedded processorsare used to monitor sensors. The microprocessor will eitherdigitize and filter the sensor signals, or it will read the signals&produce status outputs.

Graphics

Processing of digital graphics is an area where specialized

processor units are frequently employed. With the advent ofdigital television, graphics processors are becoming morecommon. In digital video, a million pixels or more need to beprocessed for every single frame


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Abstraction Layers

qComputer systems are developed in layers known as layers of abstraction.

qIt allow people to develop computer components (hardware and software) without

having to worry about the internal design of the other layers in the system.

qAt the highest level are the user-interface programs that people use on their

computers.

qAt the lowest level are the transistor layouts of the individual computer

components.


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Moore's LawA common law that governs the world of microprocessors is Moore's Law.It states that the number of transistors on a single chip at the same price will double

every 18 to 24 months.

Current microprocessor chips contain millions of transistors and the number isgrowing rapidly.


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Clock Rates

Microprocessors are typically discussed in terms of their clock speed.

It is measured in hertz (or MHz or GHz). A hertz is a "cycle per second".clock rate is speed at which microprocessor executes instructions

Faster the clock more instructions the CPU can execute per second

Von Neumann Architecture Early computer programs were hard wired. To reprogram a computer meant

changing the hardware switches manually, that took a long time with potential

errors. Computer memory was only used for storing data.

John von Neumann suggested that data and programs should be stored togetherin memory, it is now called Von Neumann architecture.


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A Von Neumann microprocessor is a processor that follows this pattern:


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The Harvard architecture is a computer architecture with physically separatestorage and signal pathways for instructions and data. The term originated from

the harvard mark-1 relay-based computer

HARVARD ARCHITECTURE


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ontrast with von Neumann architectures

Under pure VON NEUMAN architecture the CPU can be either reading aninstruction or reading/writing data from/to the memory. Both cannot occur at thesame time since the instructions and data use the same bus system.

In a computer using the Harvard architecture, the CPU can both read aninstruction and perform a data memory access at the same time, even without acache.

A Harvard architecture computer can thus be faster for a given circuit complexity


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Contrast with Modified Harvard architecture

A modified harvard architecture machine is very much like a Harvardarchitecture machine

The most common modification includes separate instruction and data cachesbacked by a common address space.

While the CPU executes from cache, it acts as a pure Harvard machine, Whenaccessing backing memory, it acts like a von Neumann machine

This modification is widespread in modern processors such as the ARMarchitecture and X86 processors. It is sometimes loosely called a Harvard

architecture, overlooking the fact that it is actually "modified".


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Microprocessor selectionSELECTION CRITERIA

Speed compatibility of the microprocessor with peripherals.

The time-critical behaviour of the application.

The size of the program required to implement certain functions.

Price

Power consumption

Performance

Availability Software support

Code density

FACTORS TO BE CONSIDERD WHILE SELECTINGTHE MICROPROCESSOR


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RISC PROCESSOR

It is an acronym for Reduced Instruction Set Computer, emphasizes simplicity &efficiency

Objective is to maximize speed by reducing clock cycle per instructionConsidering any assembly level language program it uses MOV instruction more

frequently than MUL instruction than there is gain in speedEx- SPARC, IBM, motorolas power PCs & ARM based processors

Salient features of a RISC processor are as follows-

These are designed using hard-wired ctrl. For ex- one bit dedicated for oneinstruction

All RISC instructions have fixed formats, no microcode is requiredIt executes most of the instructions in a single clock cycle

It includes only register to register load & storeIt has several general purpose registers &/ large cache memories, which supportsfast access of data

S/W can take advantage of more concurrency


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Advantages of RISC

Advantages of a reduced instruction set machine:FasterSimple hardwareShorter design cycle due to simpler hardware

Disadvantages of RISC

Drawbacks of a reduced instruction set computer includeProgrammer must pay close attention to instruction scheduling so that the

processor does not spend a large amount of time waiting for an instruction toexecute

Debugging can be difficult due to the instruction scheduling Require very fastmemory systems to feed them instructions


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CISC PROCESSOR

vit is an acronym for Complex Instruction Set ComputervEmphasis is to build complex instruction directly into hardwarevEach instruction can execute several low level instructionsvCompiler has to do a very little work to translate high level into assemblyvDue to length of the code is short, very little RAM is required to store instructionsvEx-CDC 6600, system/360, VAX, PDP-11, INTEL & AMDvAdvantages of complex instruction set machines (CISC)

vLess expensive due to the use of microcode; no need to hardwire a control unitvFewer instructions could be used to implement a given task, allowing for more

efficient use of memoryvSimplified compiler, because the micro program instruction sets could be written to

match the constructs of high-level languages

vMore instructions can fit into the cache, since the instructions are not a fixed size


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Disadvantages of CISC

vAlthough the CISC philosophy did much to improve computer performance,

it still had its drawbacks:

vInstruction sets and chip hardware became more complex with each

generation of computers, since earlier generations of a processor family

were contained as a subset in every new version

vDifferent instructions take different amount of time to execute due to their

variable-length

vMany instructions are not used frequently; Approximately 20% of the

available instructions are used in a typical program


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The design description for an IC described in terms of 3 domains

qBehavioral domain- one is free to choose a sequential or parallel algorithmwhich is available

qStructural domain- the decision about particular logic family , clocking strategyor ckt style to use is initially unbound

qPhysical domain- it provides how the ckt is implemented in terms of chips,boards & cabinets to designer

These domains are hierarchically divided into levels of design abstraction-

qArchitectural or functional level

qRegister-transfer level (RTL)

qLogic level

qCircuit level


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Design capture tool

qHDL DesignqSchematic design

qLayout designqFloor PlanningqChip Composition


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HDL Design

Wide variety of languages include:Hardware description language (HDL)

VHDL, ELLA, VerilogPopular HDL catering for hardware notion, such as bit vector,signals, and time within the native languageRuntime operating support, include compilers, debuggers andsimulators

Modified high level language- C, Pascal & LispElements of modern computer language, e.g. structure,parametization, conditionals, looping and hierarchy


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Schematic Design

Traditional method to capture a digital system

Easy to understand but HDL are more easily modified


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Layout Design

Layout can be captured via code or interactive graphics editors

Good color editor is a strong requirement

Layout editor:

interface to Design Rule Checking (DRC) program to allow interactive

checking of DRC error

layout extraction program to examine circuit connectivity issues


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Floor Planning

Exercise of blocks arranging of layoutwithin a chip to minimize area ormaximize speedFloor planning editor provide:

graphical feedback about the size

& placement of modules withoutshowing internal layout detailsConnectivity info betweenmodules in the form of rats nestwiring diagramRelative density of wiringColor display of routing densitythat allows designer to replace

and re-route to achieve betterplacement and routing


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Structural to layout synthesisA network of logic gates and registers is available it automatically converted

into layoutGate arrays & standard cell design use this approachThere are two main phases- Placement & Routing

PLACEMENTIt is a task of placing modules together to minimize area or cycle timeTwo main algorithms are there-

Min-cut algorithm- it takes blocks at top level of chip to be placed and findequal area grouping with minimum signal interconnection.it is very fast &givesgood placement

Thermal annealing- another technique in which the movement of modulesis likened to thermal annealing also used. As the layout cools the routing & timingimproves. To avoid minima the melt is heated & then re-cooled base on annealing

schedule

ROUTINGIt takes a module placement and list of connections and connects modules with

wiresTypes of routers include channel router, switch box router & maze routerTechnology is mature


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D

Chip Composition

Similar to structural synthesis,where wiring is applied on the topmodules in a design

Mainly of routing modulestogether and placing a pad ringaround the completed chip core

A B C

D

E F

A B C

D

E F


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Design Verification Tools

Simulation:

It is used to predict and verify the performance of the cktIt is used to model real time systemsLogic simulator can be easily expressed or characterized in terms offunctional blocksTiming simulator allow down to a transistor level for the most digital cktSince there are no. of transistor on the ckt so complexity is increased though

the ckt simulator will simulate in short period of time

It can be done in four levels-Circuit LevelTimingLogic level

Switch Level


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Design Economics

IC design must able to predict the cost andtime to design a particular IC

:Guide for estimating IC selling priceSTOTAL = CTOTAL / ( )1 m

where CTOTAL is manufacturing cost of a single ICand m is desire profit margin

:Cost to produce IC generally divide into- ( )Non Recurring costs NREs

Recurring cost

Fixed cost


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Design Economics

+NRE includes engineering design cost prototype manufacturing

cost :Recurring CostsCprocess + Cpackage + CtestCprocess = ( + ) / ( W P NYwYpaYft)

Where W is wafer costP is processing costN is gross die per wafer

Ywis die yield per waferYpais packaging yieldYftis final test yield

:Fixed CostsSupport cost

Cost of Sales


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ALU is a building block of several circuits.Design consists of different kinds of logic Look Ahead Carry Generatorlogic, Full adder, Subtractor, Transfer Data, DFF, Super Buffer, MUX,Transmission gate, Decoders, Inv, Nand, Nor, Ex-Or, etc.

Block Diagram

Decoder SupeBuffer

arryGenerator Adder

XOR AND OR INV -UX 2

Subtract&rTransfer

Arithmetic Unit

Logical Unit


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Schematic of alu


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Arithmetic Unit


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Logical Unit

Layout


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Layout


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References :-

wikipedia.org8085 - Ramesh GaonkarCMOS VLSI Design - Neil H.E. Westewikibooks.orgMicroprocessor by A.K. mainiLecture notes by Manish Kumar IISc Banglore.


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Thank youfor your

endurance

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