集成电路设计-09-版图设计

EIS-WuhanUniversity1集成电路设计第九章版图设计EIS-WuhanUniversity2outlineFloor-PlanningBlockPlacement.GlobalRouting.SwitchboxRouting.EIS-WuhanUniversity3布图规划Floorplanning输入层次化网表描述模块间的互联，模块内逻辑单元及互联逻辑网表—物理描述的转换。布置模块、焊盘、电源、时钟。EIS-WuhanUniversity4datapathRAMstdcellfloorplanblocksEIS-WuhanUniversity5FloorplanningstrategiesFloorplanningmusttakeintoaccountblocksofvaryingfunction,size,shape.Mustdesign:spaceallocation;signalrouting;powersupplyrouting;clockdistribution.EIS-WuhanUniversity6PurposesoffloorplanningEarlyindesign:Prepareafloorplantobudgetarea,wirearea/delay.Tradeoffsbetweenblockscanbenegotiated.Lateindesign:Makesurethepiecesfittogetherasplanned.Implementthegloballayout.EIS-WuhanUniversity7PlaceandRouteEIS-WuhanUniversity8LayoutsynthesisTwocriticalphasesoflayoutdesign:placementofcomponentsonthechip;routingofwiresbetweencomponents.Placementandroutinginteract,butseparatinglayoutdesignintophaseshelpsusunderstandtheproblemandfindgoodsolutions.EIS-WuhanUniversity9布局Placement根据布图规划，布置模块内逻辑单元。目标：可布线最小延迟最小尺寸最小电压衰减EIS-WuhanUniversity10PlacementmetricsQualitymetricsforlayout:area;delay.Areaanddelaydeterminedinpartbywiring.Howdowejudgeaplacementwithoutwiring?Estimatewirelengthwithoutactuallyperformingrouting.EIS-WuhanUniversity11WirelengthasaqualitymetricbadplacementgoodplacementEIS-WuhanUniversity12WirelengthmeasuresEstimatewirelengthbydistancebetweencomponents.Possibledistancemeasures:Euclideandistance(sqrt(x2+y2));Manhattandistance(x+y).Multi-pointnetsmustbebrokenupintotreesforgoodestimates.EIS-WuhanUniversity13PlacementtechniquesCanconstructaninitialsolution,improveanexistingsolution.Pairwiseinterchangeisasimpleimprovementmetric:Interchangeapair,keeptheswapifithelpswirelength.Heuristicdetermineswhichtwocomponentstoswap.EIS-WuhanUniversity14PlacementbypartitioningWorkswellforcomponentsoffairlyuniformsize.Partitionnetlisttominimizetotalwirelengthusingmin-cutcriterion.Partitioningmaybeinterpretedas1-Dor2-Dlayout.EIS-WuhanUniversity15Min-cutbisectingpartitioningpartition1partition2ABCD3nets1netEIS-WuhanUniversity16Min-cutbisectingpartitioningSwappingAandB:Bdrags1net;Adrags3nets;totalcutincrease:4nets.Conclusion:probablynotagoodswap,butmustbecomparedwithotherpairs.EIS-WuhanUniversity17BlockplacementBlockshave:area;aspectratio.Blocksmaybeplacedatdifferentrotationsandreflections.Uniformsizeblocksareeasiertointerchange.EIS-WuhanUniversity18BlocksandwiringCannotignorewiringduringblockplacement—largewiringareasmayforcerearrangementofblocks.Wiringplanmustconsiderareaanddelayofcriticalsignals.Blocksdividewiringareaintoroutingchannels.EIS-WuhanUniversity19ChanneldefinitionChannelsendatblockboundaries.Severalalternatechanneldefinitionsarepossible:ABCchannel1ch2ch1ch2ch3EIS-WuhanUniversity20ChanneldefinitionchangeswithblockspacingChangingspacingchangesrelationshipbetweenblockedges:ABCCEIS-WuhanUniversity21ChannelgraphABCDEEIS-WuhanUniversity22ChannelgraphusageNodesarechannels,edgesplacedbetweentwochannelsthattouch.Channelgraphshowspathsbetweenchannels.Channelgraphcanbeusedtoguideglobalrouting.EIS-WuhanUniversity23ChannelsmustberoutedinorderWireoutofendofonechannelcreatespinonsideofnextchannel:channelAchannelBconstraintEIS-WuhanUniversity24WindmillsCancreateanunroutablecombinationofchannelswithcircularconstraints:ABCDEIS-WuhanUniversity25SlicablefloorplanEIS-WuhanUniversity26SlicabilitypropertyAslicablefloorplancanberecursivelycutintwowithoutcuttinganyblocks.Aslicablefloorplanisguaranteedtohavenowindmills,thereforeguaranteedtohaveafeasibleorderofroutingforthechannels.Slicabilityisadesirablepropertyforfloorplans.EIS-WuhanUniversity27Routing目标：Completepower/ground/clockroutingCompleteroutingconformingtospecifiedwiringrulesandordersEIS-WuhanUniversity28RoutingMajorphasesinrouting:globalroutingassignsnetstoroutingareas;detailedroutingdesignstheroutingareas.Netorderingisamajorproblem.Orderinwhichnetsarerouteddeterminesqualityofresult.Netorderingisaheuristic.EIS-WuhanUniversity29GlobalroutingGoal:assignwirestopathsthroughchannels.Don’tworryaboutexactroutingofwireswithinchannel.Canestimatechannelheightfromglobalroutingusingcongestion.EIS-WuhanUniversity30DetailedroutingDoglegrouterbreaksnetintomultiplesegmentsasneeded.Trytominimizenumberofdoglegsegmentspernettominimizecongestionforfuturenets.Onegoodheuristic—useleft-edgecriteriononeachdoglegsegmenttofillupthechannel.EIS-WuhanUniversity31MazeroutingWillfindshortestpathforasinglewire,ifsuchapathexists.Twophases:Labelnodeswithdistance,radiatingfromsource.Usedistancestotracefromsinktosource,choosingapaththatalwaysdecreasesdistancetosource.EIS-WuhanUniversity32MazeroutingexampleEIS-WuhanUniversity33LineproberoutingHeuristicmethodforfindingashortroute.Workswitharbitrarycombinationofobstacles.Doesnotexploreallpossiblepaths—notoptimal.EIS-WuhanUniversity34LineprobeexampleAAline1line2EIS-WuhanUniversity35ChannelutilizationWanttokeepallchannelsaboutequallyfulltominimizewastedarea.Importanttoroutetime-criticalsignalsfi