October 18, 2007 1

FPGAs : An Overview

Sanjiv Malik

October 18, 2007 2

What is Programmable Logic?

Can be defined as an IC whose functionality can be modified “On-the fly”

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Field Programmable Gate Arrays

FPGA is an IC with ability to reconfigure its circuitry for a desired application or function at any time after manufacturingAdaptive hardware that continuously changes in response to the input data or processing environmentCombination of general-purpose processors and ASICs(Application Specific IC). Quick reconfiguration time, in order of 100 µS to 1 mS

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FPGA Facts

• You can download FPGAs as many time as you want -no limit - with different functionalities every time if you want. If you make a mistake in your design, just fix your "logic function", re-compile and re-download it. No PCB, solder or component to change.

• The designs can run much faster than if you were to design a board with discrete components, since everything runs within the FPGA, on its silicon die.

• FPGAs loose their functionality when the power goes away (like RAM in a computer that looses its content). You have to re-download them when power goes back up to restore the functionality.

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FPGA Facts (Cont..)

• FPGAs Evolved from PALs, PLDs, Complex PLDs• FPGAs comparison to other options

– FPGA Strengths: quick prototyping and time-to-market,reprogrammability, relatively easy to use

– FPGA Weaknesses: cost, density, speed• FPGA Vendors: Xilinx, Altera, Actel, Atmel, Lucent,

Cypress, QuickLogic, IBM, Motorola

Technology Gates Speed NRE Cost Part Cost Spin timeCustom VLSI <10M <500 MHz $20K-$100M $1-up weeksGate array <2M <200 MHz $10K-$1M $1-up days/weeksFPGA <100K <100 MHz $100-$100K $10-$1K minutes/hours

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FPGAs vs CPLDs

• FPGAs are "fine-grain" devices. That means that they contain a lot (up to 100000) of tiny blocks of logic with flip-flops.

• FPGAs are RAM based. They need to be "downloaded" (configured) at each power-up.

• FPGAs can contain very large digital designs

• FPGAs have special routing resources to implement efficiently binary counters and arithmetic functions (adders, comparators...).

• CPLDs are "coarse-grain" devices. They contain relatively few (a few 100's max) large blocks of logic with flip-flops.

• CPLDs are EEPROM based. They are active at power-up (i.e. as long as they've been programmed at least once

• CPLDs can contain small designs only.

• CPLDs do not have

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An Example FPGA Chip

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Where are FPGAs used?

Some of the examples of FPGA usage are:Fast prototypes of large designs for simulation/ verification later to be implemented in ICsSignal, image processing: filters, warping, musicGraphics, UART and other device controllersMilitary: target dependent correlation/recognitionCryptography: DES search“Hardware” genetic algorithms

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FPGA internal design

• The basic structure of FPGAs is array-based, meaning that each chip comprises a two-dimensional array of logic blocks that can be interconnected via horizontal and vertical routing channels.

• FPGAs consists of an array of CLB, IOB and programmable interconnects

• CLB : Configurable Logic Block• IOB : Input/output block

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FPGA Internal design(Cont..)

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Control Logic Block

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Example Control Logic Block

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Input/Output Block

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FPGA Development tools

• Design tools• Pin Assignment tools• Design Entry tools• Simulation tools• Synthesis tools

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FPGA Programming Steps

1. Use a computer to describe the "logic function" that you want. You might draw a schematic, or create a text file describing the function, doesn't matter.

2. Compile the "logic function" on your computer, using a software provided by the FPGA vendor. That creates a binary file that can be downloaded into the FPGA.

3. Connect a cable from your computer to the FPGA, and download the binary file to the FPGA.

4. That's it! Your FPGA behaves according to your "logic function".

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Our Sample Board

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Step 1: Creating the logic[VHDL)

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Advance FPFA based system designs

• For designing microprocessor-based complex embedded systems, advance FPGAs are available.

• These contains gates of the order of TODO• Xilings and vendors provide system design

wizards to create complex systems.

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Xilings FPGA based Advance system design

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Xilings FPGA based Advance system design(Cont…)

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Xilings FPGA based Advance system design(Cont…)

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Conclusion

• Over time FPGAs will become the dominant form of digital logic design and implementation.

• Their ease of access, principally through the low cost of the devices, makes them attractive to small firms and small parts of large companies.

• The fast manufacturing turn-around they provide is an essential element of success in the market.

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