Fieldprogrammable gate array.docx
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Fieldprogrammable gate array.docx
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Fieldprogrammablegatearray
Field-programmablegatearray
"FPGA"redirectshere.ItisnottobeconfusedwithFlip-chippingridarray.
AnAlteraStratixIVGXFPGA.
AnexampleofanFPGAboard.
Afield-programmablegatearray(FPGA)isanintegratedcircuitdesignedtobeconfiguredbythecustomerordesigneraftermanufacturing—hence"field-programmable".TheFPGAconfigurationisgenerallyspecifiedusingahardwaredescriptionlanguage(HDL),similartothatusedforanapplication-specificintegratedcircuit(ASIC)(circuitdiagramswerepreviouslyusedtospecifytheconfiguration,astheywereforASICs,butthisisincreasinglyrare).FPGAscanbeusedtoimplementanylogicalfunctionthatanASICcouldperform.Theabilitytoupdatethefunctionalityaftershipping,andthelownon-recurringengineeringcostsrelativetoanASICdesign(notwithstandingthegenerallyhigherunitcost),offeradvantagesformanyapplications.[1]
FPGAscontainprogrammablelogiccomponentscalled"logicblocks",andahierarchyofreconfigurableinterconnectsthatallowtheblockstobe"wiredtogether"—somewhatlikeaone-chipprogrammablebreadboard.Logicblockscanbeconfiguredtoperformcomplexcombinationalfunctions,ormerelysimplelogicgateslikeANDandXOR.InmostFPGAs,thelogicblocksalsoincludememoryelements,whichmaybesimpleflip-flopsormorecompleteblocksofmemory.[1]
Contents
[hide]
∙1History
o1.1Moderndevelopments
o1.2Gates
o1.3Marketsize
o1.4FPGAdesignstarts
∙2FPGAcomparisons
o2.1VersusCPLDs
o2.2Securityconsiderations
∙3Applications
∙4Architecture
∙5FPGAdesignandprogramming
∙6Basicprocesstechnologytypes
∙7Majormanufacturers
∙8Seealso
∙9References
∙10Externallinks
[edit]History
TheFPGAindustrysproutedfromprogrammablereadonlymemory(PROM)andprogrammablelogicdevices(PLDs).PROMsandPLDsbothhadtheoptionofbeingprogrammedinbatchesinafactoryorinthefield(fieldprogrammable),howeverprogrammablelogicwashard-wiredbetweenlogicgates.[2]
XilinxCo-Founders,RossFreemanandBernardVonderschmitt,inventedthefirstcommerciallyviablefieldprogrammablegatearrayin1985–theXC2064.[3]TheXC2064hadprogrammablegatesandprogrammableinterconnectsbetweengates,thebeginningsofanewtechnologyandmarket.[4]TheXC2064boastedamere64configurablelogicblocks(CLBs),withtwo3-inputlookuptables(LUTs).[5]Morethan20yearslater,FreemanwasenteredintotheNationalInventor'sHallofFameforhisinvention.[6]
Someoftheindustry’sfoundationalconceptsandtechnologiesforprogrammablelogicarrays,gates,andlogicblocksarefoundedinpatentsawardedtoDavidW.PageandLuVerneR.Petersonin1985.[7][8]
Inthelate1980stheNavalSurfaceWarfareDepartmentfundedanexperimentproposedbySteveCasselmantodevelopacomputerthatwouldimplement600,000reprogrammablegates.Casselmanwassuccessfulandthesystemwasawardedapatentin1992.[2]
Xilinxcontinuedunchallengedandquicklygrowingfrom1985tothemid-1990s,whencompetitorssproutedup,erodingsignificantmarket-share.By1993,Actelwasservingabout18percentofthemarket.[4]
The1990swereanexplosiveperiodoftimeforFPGAs,bothinsophisticationandthevolumeofproduction.Intheearly1990s,FPGAswereprimarilyusedintelecommunicationsandnetworking.Bytheendofthedecade,FPGAsfoundtheirwayintoconsumer,automotive,andindustrialapplications.[9]
FPGAsgotaglimpseoffamein1997,whenAdrianThompsonmergedgeneticalgorithmtechnologyandFPGAstocreateasoundrecognitiondevice.Thomson’salgorithmconfiguredanarrayof10x10cellsinaXilinxFPGAchiptodiscriminatebetweentwotones,utilisinganaloguefeaturesofthedigitalchip.[10][2]
[edit]Moderndevelopments
Arecenttrendhasbeentotakethecoarse-grainedarchitecturalapproachastepfurtherbycombiningthelogicblocksandinterconnectsoftraditionalFPGAswithembeddedmicroprocessorsandrelatedperipheralstoformacomplete"systemonaprogrammablechip".ThisworkmirrorsthearchitecturebyRonPerlofandHanaPotashofBurroughsAdvancedSystemsGroupwhichcombinedareconfigurableCPUarchitectureonasinglechipcalledtheSB24.Thatworkwasdonein1982.ExamplesofsuchhybridtechnologiescanbefoundintheXilinxVirtex-IIPROandVirtex-4devices,whichincludeoneormorePowerPCprocessorsembeddedwithintheFPGA'slogicfabric.TheAtmelFPSLICisanothersuchdevice,whichusesanAVRprocessorincombinationwithAtmel'sprogrammablelogicarchitecture.
Analternateapproachtousinghard-macroprocessorsistomakeuseof"soft"processorcoresthatareimplementedwithintheFPGAlogic.(See"Softprocessors"below).
Aspreviouslymentioned,manymodernFPGAshavetheabilitytobereprogrammedat"runtime,"andthisisleadingtotheideaofreconfigurablecomputingorreconfigurablesystems—CPUsthatreconfigurethemselvestosuitthetaskathand.TheMitrionVirtualProcessorfromMitrionicsisanexampleofareconfigurablesoftprocessor,implementedonFPGAs.However,itdoesnotsupportdynamicreconfigurationatruntime,butinsteadadaptsitselftoaspecificprogram.
Additionally,new,non-FPGAarchitecturesarebeginningtoemerge.Software-configurablemicroprocessorssuchastheStretchS5000adoptahybridapproachbyprovidinganarrayofprocessorcoresandFPGA-likeprogrammablecoresonthesamechip.XilinxandAlteraaresomeofthemajorFPGAchipmakers.
[edit]Gates
∙1987:
9,000gates,Xilinx[4]
∙1992:
600,000,NavalSurfaceWarfareDepartment[2]
∙Early2000s:
Millions[9]
[edit]Marketsize
∙1985:
FirstcommercialFPGAtechnologyinventedbyXilinx[4]
∙1987:
$14million[4]
∙~1993:
>$385million[4]
∙2005:
$1.9billion[11]
∙2010estimates:
$2.75billion[11]
[edit]FPGAdesignstarts
∙10,000[12]
∙2005:
80,000[13]
∙2008:
90,000[14]
∙2010estimates:
110,000[13]
[edit]FPGAcomparisons
Historically,FPGAshavebeenslower,lessenergyefficientandgenerallyachievedlessfunctionalitythantheirfixedASICcounterparts.Acombinationofvolume,fabricationimprovements,researchanddevelopment,andtheI/OcapabilitiesofnewsupercomputershavelargelyclosedtheperformancegapbetweenASICsandFPGAs.[15]
Advantagesincludeashortertimetomarket,abilitytore-programinthefieldtofixbugs,andlowernon-recurringengineeringcosts.VendorscanalsotakeamiddleroadbydevelopingtheirhardwareonordinaryFPGAs,butmanufacturetheirfinalversionsoitcannolongerbemodifiedafterthedesignhasbeencommitted.
XilinxclaimsthatseveralmarketandtechnologydynamicsarechangingtheASIC/FPGAparadigm:
[16]
∙ICcostsarerisingaggressively
∙ASICcomplexityhasbolstereddevelopmenttimeandcosts
∙R&Dresourcesandheadcountisdecreasing
∙Revenuelossesforslowtime-to-marketareincreasing
∙Financialconstraintsinapooreconomyaredrivinglow-costtechnologies
ThesetrendsmakeFPGAsabetteralternativethanASICsforagrowingnumberofhigher-volumeapplicationsthantheyhavebeenhistoricallyusedfor,towhichthecompanyattributesthegrowingnumberofFPGAdesignstarts(seeHistory).[16]
SomeFPGAshavethecapabilityofpartialre-configurationthatletsoneportionofthedevicebere-programmedwhileotherportionscontinuerunning.
[edit]VersusCPLDs
TheprimarydifferencesbetweenCPLDsandFPGAsarearchitectural.ACPLDhasasomewhatrestrictivestructureconsistingofoneormoreprogrammablesum-of-productslogicarraysfeedingarelativelysmallnumberofclockedregisters.Theresultofthisislessflexibility,withtheadvantageofmorepredictabletimingdelaysandahigherlogic-to-interconnectratio.TheFPGAarchitectures,ontheotherhand,aredominatedbyinterconnect.Thismakesthemfarmoreflexible(intermsoftherangeofdesignsthatarepracticalforimplementationwithinthem)butalsofarmorecomplextodesignfor.
AnothernotabledifferencebetweenCPLDsandFPGAsisthepresenceinmostFPGAsofhigher-levelembeddedfunctions(suchasaddersandmultipliers)andembeddedmemories,aswellastohavelogicblocksimplementdecodersormathematicalfunctions.
[edit]Securityconsiderations
Withrespecttosecurity,FPGAshavebothadvantagesanddisadvantagesascomparedtoASICsorsecuremicroprocessors.FPGAs'flexibilitymakesmaliciousmodificationsduringfabricationalowerrisk.[17]FormanyFPGAs,theloadeddesignisexposedwhileitisloaded(typicallyoneverypower-on).Toaddressthisissue,someFPGAssupportbitstreamencryption.
[edit]Applications
ApplicationsofFPGAsincludedigitalsignalprocessing,software-definedradio,aerospaceanddefensesystems,ASICprototyping,medicalimaging,computervision,speechrecognition,cryptography,bioinformatics,computerhardwareemulation,radioastronomy,metaldetectionandagrowingrangeofotherareas.
FPGAsoriginallybeganascompetitorstoCPLDsandcompetedinasimilarspace,thatofgluelogicforPCBs.Astheirsize,capabilities,andspeedincreased,theybegantotakeoverlargerandlargerfunctionstothestatewheresomearenowmarketedasfullsystemsonchips(SoC).ParticularlywiththeintroductionofdedicatedmultipliersintoFPGAarchitecturesinthelate1990s,applications,whichhadtraditionallybeenthesolereserveofDSPs,begantoincorporateFPGAsinstead.[18][19]
FPGAsespeciallyfindapplicationsinanyareaoralgorithmthatcanmakeuseofthemassiveparallelismofferedbytheirarchitecture.Onesuchareaiscodebreaking,inparticularbrute-forceattack,ofcryptographicalgorithms.
FPGAsareincreasinglyusedinconventionalhighperformancecomputingapplicationswherecomputationalker
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