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1、CHAPTER1VerilogDesignintheRealWorldThechallengesfacingdigitaldesignengineersintheRealWorldhavechangedastechnologyhasadvanced.Designsarefaster,uselargernumbersofgates,andarephysicallysmaller.Packageshavemanyfine-pitchpins.However,theunderlyingdesignconcernshavenotchanged,norwilltheyc
2、hangeinthefuture.Thedesignermustcreatedesignsthat:·areunderstandabletootherswhowillworkonthedesignlater.·arelogicallycorrect.Thedesignmustactuallyimplementthespecifiedlogiccorrectly.Thedesignercollectsuserspecifications,deviceparameters,anddesignentryrules,thencreatesadesignthatmeet
3、stheneedsoftheenduser.·performunderworst-caseconditionsoftemperatureandprocessvariation.Asdevicesageandareexposedtochangesintemperature,theperformanceofthecircuitelementschange.Temperaturechangescanbeself-generatedorcausedbyexternalheatsources.Notwodevicesareexactlyequivalent,partic
4、ularly12VerilogDesignintheRealWorldChapter1devicesthatweremanufacturedatdifferenttimes,perhapsatdifferentfoundriesandperhapswithdifferentdesignrules.Variationsinthedevicetimingspecifications,includingclockskew,registersetupandholdtimes,propagationdelaytimes,andoutputrise/falltimesmu
5、stbeaccountedfor.·arereliable.Theenddesigncannotexceedthepackagepowerdissipationlimits.Eachdevicehasanoperationaltemperaturerange.Forexample,adeviceratedforcommercialoperationhasatemperatureratingof0to70degreesC(32to160degreesF).Thedevicetemperatureincludestheambienttemperature(thet
6、emperatureoftheairsurroundingtheproductwhenitisinuse),temperatureincreasesduetoheat-generatingsourcesinsidetheproduct,andheatgeneratedbythedevicesofthedesignitself.Internallygeneratedtemperaturerisesareproportionaltothenumberofgatesandthespeedatwhichtheyarechangingstates.·donotgener
7、atemoreEMI/RFIthannecessarytoaccomplishthejobandmeetEMI/RFIspecifications.·aretestableandcanbeproventomeetthespecifications.·donotexceedthepowerconsumptiongoals(forexample,inabattery-operatedcircuit).Theserequirementsexistregardlessofthefinalformofthedesignandregardlessoftheengineer
8、ingtoolsusedtocreat
