集成电路设计-09-版图设计

EIS-WuhanUniversity,1,集成电路设计,第九章版图设计,EIS-WuhanUniversity,2,outline,Floor-PlanningBlockPlacement.GlobalRouting.SwitchboxRouting.,EIS-WuhanUniversity,3,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-WuhanUniversity,4,datapath,RAM,stdcell,floorplan,blocks,EIS-WuhanUniversity,5,Floorplanningstrategies,Floorplanningmusttakeintoaccountblocksofvaryingfunction,size,shape.Mustdesign:spaceallocation;signalrouting;powersupplyrouting;clockdistribution.,EIS-WuhanUniversity,6,Purposesoffloorplanning,Earlyindesign:Prepareafloorplantobudgetarea,wirearea/delay.Tradeoffsbetweenblockscanbenegotiated.Lateindesign:Makesurethepiecesfittogetherasplanned.Implementthegloballayout.,EIS-WuhanUniversity,7,PlaceandRoute,EIS-WuhanUniversity,8,Layoutsynthesis,Twocriticalphasesoflayoutdesign:placementofcomponentsonthechip;routingofwiresbetweencomponents.Placementandroutinginteract,butseparatinglayoutdesignintophaseshelpsusunderstandtheproblemandfindgoodsolutions.,EIS-WuhanUniversity,9,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-WuhanUniversity,10,Placementmetrics,Qualitymetricsforlayout:area;delay.Areaanddelaydeterminedinpartbywiring.Howdowejudgeaplacementwithoutwiring?Estimatewirelengthwithoutactuallyperformingrouting.,EIS-WuhanUniversity,11,Wirelengthasaqualitymetric,badplacement,goodplacement,EIS-WuhanUniversity,12,Wirelengthmeasures,Estimatewirelengthbydistancebetweencomponents.Possibledistancemeasures:Euclideandistance(sqrt(x2+y2);Manhattandistance(x+y).Multi-pointnetsmustbebrokenupintotreesforgoodestimates.,EIS-WuhanUniversity,13,Placementtechniques,Canconstructaninitialsolution,improveanexistingsolution.Pairwiseinterchangeisasimpleimprovementmetric:Interchangeapair,keeptheswapifithelpswirelength.Heuristicdetermineswhichtwocomponentstoswap.,EIS-WuhanUniversity,14,Placementbypartitioning,Workswellforcomponentsoffairlyuniformsize.Partitionnetlisttominimizetotalwirelengthusingmin-cutcriterion.Partitioningmaybeinterpretedas1-Dor2-Dlayout.,EIS-WuhanUniversity,15,Min-cutbisectingpartitioning,partition1,partition2,A,B,C,D,EIS-WuhanUniversity,16,Min-cutbisectingpartitioning,SwappingAandB:Bdrags1net;Adrags3nets;totalcutincrease:4nets.Conclusion:probablynotagoodswap,butmustbecomparedwithotherpairs.,EIS-WuhanUniversity,17,Blockplacement,Blockshave:area;aspectratio.Blocksmaybeplacedatdifferentrotationsandreflections.Uniformsizeblocksareeasiertointerchange.,EIS-WuhanUniversity,18,Blocksandwiring,Cannotignorewiringduringblockplacementlargewiringareasmayforcerearrangementofblocks.Wiringplanmustconsiderareaanddelayofcriticalsignals.Blocksdividewiringareaintoroutingchannels.,EIS-WuhanUniversity,19,Channeldefinition,Channelsendatblockboundaries.Severalalternatechanneldefinitionsarepossible:,A,B,C,EIS-WuhanUniversity,20,Channeldefinitionchangeswithblockspacing,Changingspacingchangesrelationshipbetweenblockedges:,A,B,C,EIS-WuhanUniversity,21,Channelgraph,A,B,C,D,E,EIS-WuhanUniversity,22,Channelgraphusage,Nodesarechannels,edgesplacedbetweentwochannelsthattouch.Channelgraphshowspathsbetweenchannels.Channelgraphcanbeusedtoguideglobalrouting.,EIS-WuhanUniversity,23,Channelsmustberoutedinorder,Wireoutofendofonechannelcreatespinonsideofnextchannel:,channelA,channelB,constraint,EIS-WuhanUniversity,24,Windmills,Cancreateanunroutablecombinationofchannelswithcircularconstraints:,A,B,C,D,EIS-WuhanUniversity,25,Slicablefloorplan,EIS-WuhanUniversity,26,Slicabilityproperty,Aslicablefloorplancanberecursivelycutintwowithoutcuttinganyblocks.Aslicablefloorplanisguaranteedtohavenowindmills,thereforeguaranteedtohaveafeasibleorderofroutingforthechannels.Slicabilityisadesirablepropertyforfloorplans.,EIS-WuhanUniversity,27,Routing,目标：Completepower/ground/clockroutingCompleteroutingconformingtospecifiedwiringrulesandorders,EIS-WuhanUniversity,28,Routing,Majorphasesinrouting:globalroutingassignsnetstoroutingareas;detailedroutingdesignstheroutingareas.Netorderingisamajorproblem.Orderinwhichnetsarerouteddeterminesqualityofresult.Netorderingisaheuristic.,EIS-WuhanUniversity,29,Globalrouting,Goal:assignwirestopathsthroughchannels.Dontworryaboutexactroutingofwireswithinchannel.Canestimatechannelheightfromglobalroutingusingcongestion.,EIS-WuhanUniversity,30,Detailedrouting,Doglegrouterbreaksnetintomultiplesegmentsasneeded.Trytominimizenumberofdoglegsegmentspernettominimizecongestionforfuturenets.Onegoodheuristicuseleft-edgecriteriononeachdoglegsegmenttofillupthechannel.,EIS-WuhanUniversity,31,Mazerouting,Willfindshortestpathforasinglewire,ifsuchapathexists.Twophases:Labelnodeswithdistance,radiatingfromsource.Usedistancestotracefromsinktosource,choosingapaththatalwaysdecreasesdistancetosource.,EIS-WuhanUniversity,32,Mazeroutingexample,EIS-WuhanUniversity,33,Lineproberouting,Heuristicmethodforfindingashortroute.Workswitharbitrarycombinationofobstacles.Doesnotexploreallpossiblepathsnotoptimal.,EIS-WuhanUniversity,34,Lineprobeexample,A,A,line1,line2,EIS-WuhanUniversity,35,Channelutilization,Wanttokeepallchannelsaboutequallyfulltominimizewastedarea.Importanttoroutetime-criticalsignalsfirst.Shortestpathmaynotbebestforglobalwiring.Ingeneral,mayneedtorip-upwiresandreroutetoimprovetheglobalrouting.,EIS-WuhanUniversity,36,Typesofrouting,Channelrouting:channelmaygrowinonedimensiontoaccommodatewires;pinsgenerallyononlytwosides.Switchboxrouting:cannotgrowinanydimension;pinsareonallfoursides,fixingdimensionsofthebox.,EIS-WuhanUniversity,37,Channelsandswitchboxes,channel,switchbox,channel,switchboxpins,Cantexpandaswitchboxtomakeroomformorewiring.Switchboxmaybedefinedbyintersectionofchannels.,EIS-WuhanUniversity,38,Routingorderandswitchboxes,Switchboxesfrequentlyneedmoreexperimentationwithwiringorderbecausenetsmayblockothernets:,B,A,B,A,BblocksA,EIS-WuhanUniversity,39,LayoutDesign:P&RvsFullCustom,FullCustomLayoutManualdesign,MostPlacementandRouteisspecifiedbyengineer,P&RAutomatic,EIS-WuhanUniversity,40,静态时间分析（Statictiminganalyzer）calculatespoint-to-pointtimingforsynchronouscircuits:建起与保持时间（setupandholdtime）错误关键路径（criticalpath）分析延迟时间计算依据in