Ganesh's presentation

8/10/2019 Ganesh's presentation

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Vlsi means VERY LARGE SCALE INTERGRATION.

VLSI is the process of creating integrated circuits by combining thousands of transistors into asingle chip.

The Microprocessor is a vlsi device.

The size and cost of circuits is reduced by vlsi by making 1000 of circuits with diodes andresistance to a single chip.

The vlsi is designed by using HDL (HARDWARE DESCRIPTION LANGUGE).

The HDL is developed to VHDL & Verilog HDL.

The Vlsi is designed by using

1.SPLD(Simple Programming Logic Device)

2.CPLD(Complex Programming Logic Device)

3.FPGA(Field Programming Gate Array)


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HISTORY:

VLSI began in 1970s when complex semiconductor and communication technologies were being

developed.

The first integrated circuits held only a few devices, perhaps as many as

ten diodes, transistors, resistors and capacitors, making it possible to fabricate one or more logic

gates on a single device.

Current technology has moved far past this mark and today's microprocessors have many

millions of gates and billions of individual transistors.The vlsi is designed by using the MOORES LAW.

A notable example is NVidia's 280 series GPU. This GPU is unique in the fact that almost all of its

1.4 billion transistors are used for logic, in contrast to the Itanium, whose large transistor count is

largely due to its 24 MB L3 cache.

Current designs, as opposed to the earliest devices, use extensive design automation and

automated logic synthesis to lay out the transistors, enabling higher levels of complexity in the

resulting logic functionality.

VLSI technology is moving towards radical level miniaturization with introduction

of NEMS (NANOELECTROMECHANICAL SYSTEM) technology.


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Moore's lawdescribes a long-term trend in the history of computinghardware whereby the number of transistors that can be placed inexpensively onan integrated circuit doubles approximately every two years.

The capabilities of many digital electronic devices are strongly linked to Moore'slaw: processing speed, memory capacity, sensors and even the number and sizeof pixels in digital cameras.

Moore's law describes a driving force of technological and social change in the late20th and early 21st centuries.


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ASIC and FPGA design flow Advanced digital design methodologies

HDL based design methodologies

Synthesis coding styles

Place and Route - HDL based design

Static Timing Analysis

APPLICATIONS OF VLSI:

1. DSP2. Communications3. Microwave and RF4. MEMS5. Cryptography.6. Consumer Electronics

7. Automobiles8. Space Applications


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CHALLENGES:

As microprocessors become more complex due to technology scaling, microprocessor designershave encountered several challenges which force them to think beyond the design plane, and lookahead to post-silicon:

Power usage/Heat dissipationAs threshold voltages have ceased to scale with advancing processtechnology, dynamic power dissipation has not scaled proportionally. Maintaining logic complexitywhen scaling the design down only means that the power dissipation per area will go up. This hasgiven rise to techniques such as dynamic voltage and frequency scaling (DVFS) to minimize overallpower.

Process variationAs photolithography techniques tend closer to the fundamental laws of optics,

achieving high accuracy in doping concentrations and etched wires is becoming more difficult andprone to errors due to variation. Designers now must simulate across multiple fabrication processcorners before a chip is certified ready for production.

Stricter design rulesDue to lithography and etch issues with scaling, design rules for layout havebecome increasingly stringent. Designers must keep ever more of these rules in mind while layingout custom circuits. The overhead for custom design is now reaching a tipping point, with manydesign houses opting to switch to electronic design automation (EDA) tools to automate theirdesign process.

Timing/design closureAs clock frequencies tend to scale up, designers are finding it more difficultto distribute and maintain low clock skew between these high frequency clocks across the entirechip. This has led to a rising interest in multicore and multiprocessor architectures, since an overallspeedup can be obtained by lowering the clock frequency and distributing processing.


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VLSI chiefly comprises of Front End Design and Back End design these days.While front end design includes digital design using HDL, design verificationthrough simulation and other verification techniques, the design from gates anddesign for testability, backend design comprises of CMOS library design and itscharacterization.

It also covers the physical design and fault simulation.

While Simple logic gates might be considered as SSI devices and multiplexersand parity encoders as MSI, the world of VLSI is much more diverse.

Generally, the entire design procedure follows a step by step approach in whicheach design step is followed by simulation before actually being put onto thehardware or moving on to the next step.

The major design steps are different levels of abstractions of the device as awhole:


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The conversion of the netlist into its geometrical representation is done in this stepand the result is called a layout.

This step follows some predefined fixed rules like the lambda rules which provide theexact details of the size, ratio and spacing between components.

This step is further divided into sub-steps which are:

Circuit Partitioning:

Because of the huge number of transistors involved, it is not possible to handle theentire circuit all at once due to limitations on computational capabilities and memoryrequirements.

Hence the whole circuit is broken down into blocks which are interconnected.

Floor Planning and Placement:

Choosing the best layout for each block from partitioning step and the overall chip,

considering the interconnect area between the blocks, the exact positioning on thechip in order to minimize the area arrangement while meeting the performanceconstraints through iterative approach are the major design steps taken care of in thisstep.


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Routing:

The quality of placement becomes evident only after this step is completed. Routinginvolves the completion of the interconnections between modules.

This is completed in two steps.

First connections are completed between blocks without taking into considerationthe exact geometric details of each wire and pin.

Then, a detailed routing step completes point to point connections between pins onthe blocks.

Layout Compaction: The smaller the chip size can get, the better it is.

The compression of the layout from all directions to minimize the chip area therebyreducing wire lengths, signal delays and overall cost takes place in this design step.

Extraction and Verification:

The circuit is extracted from the layout for comparison with the original netlist,

performance verification, and reliability verification and to check the correctness ofthe layout is done before the final step of packaging.


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The chips are put together on a Printed Circuit Board or a Multi Chip Module toobtain the final finished product.


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VHDL stands for very high-speed integrated circuit hardware description language.Which is one of the programming language used to model a digital system bydataflow, behavioural and structural style of modeling.

This language was first introduced in 1981 for the department of Defense (DoD)under the VHSIC programme. In 1983 IBM, Texas instruments and Intermetrics startedto develop this language. In 1985 VHDL 7.2 version was released. In 1987 IEEEstandardized the language.

In the semiconductor and electronic design industry, Verilogis a hardware descriptionlanguage (HDL) used to model electronic systems.

Verilog HDL, not to be confused with VHDL (a competing language), is mostcommonly used in the design, verification, and implementation of digital logic chipsat the register-transfer level of abstraction.

It is also used in the verification of analog and mixed-signal circuits.


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The programming in vlsi can be done 3 ways. They are1. SPLD

2. CPLD

3. FPGA

SPLD:Simple programmable logic devices (SPLD) are the simplest, smallest and least-expensive forms of programmable logic devices. SPLDs can be used in boards toreplace 7400-series TTL components (AND, OR, and NOT gates).

They typically comprise 4 to 22 fully connected macrocells. These macrocells aretypically comprised of some combinatorial logic (such as AND OR gates) and a flip-

flop. In other words, a small Boolean logic equation can be built within eachmacrocell.

This equation will combine the state of some number of binary inputs into a binaryoutput and, if necessary, store that output in the flip-flop until the next clock edge.


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A complex programmable logic device (CPLD)is a programmable logic device withcomplexity between that of PALs and FPGAs, and architectural features of both.

The building block of a CPLD is the macrocell, which contains logicimplementing disjunctive normal form expressions and more specialized logicoperations.


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FPGAs contain programmable logic components called "logic blocks", and a hierarchyof reconfigurable interconnects that allow the blocks to be "wired together"somewhat like many (changeable) logic gates that can be inter-wired in (many)different configurations.

Logic blocks can be configured to perform complex combinational functions, ormerely simple logic gates like AND and XOR. In most FPGAs, the logic blocks alsoinclude memory elements, which may be simple flip-flops or more complete blocks of

memory.


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There many companies inventing new devices in compatible with VLSI but theprogrammers in the vlsi is very limited.

vlsi is a vast unit of subject but still in India programmers is very so we have to

improve our programming teqniques in vlsi.Vlsi has the vast of applications in programming and Artificial intelligence.

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Ganesh's presentation