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1.1Introduction
1.2SubmoduleOverview
Introduction
AneffectivePWMperipheralmustbeabletogeneratecomplexpulsewidthwaveformswithminimalCPU
overheadorintervention.Itneedstobehighlyprogrammableandveryflexiblewhilebeingeasyto
understandanduse.TheePWMunitdescribedhereaddressestheserequirementsbyallocatingall
neededtimingandcontrolresourcesonaperPWMchannelbasis.Crosscouplingorsharingofresources
hasbeenavoided;instead,theePWMisbuiltupfromsmallersinglechannelmoduleswithseparate
resourcesandthatcanoperatetogetherasrequiredtoformasystem.Thismodularapproachresultsin
anorthogonalarchitectureandprovidesamoretransparentviewoftheperipheralstructure,helpingusers
tounderstanditsoperationquickly.
InthisdocumenttheletterxwithinasignalormodulenameisusedtoindicateagenericePWMinstance
onadevice.ForexampleoutputsignalsEPWMxAandEPWMxBrefertotheoutputsignalsfromthe
ePWMxinstance.Thus,EPWM1AandEPWM1BbelongtoePWM1andlikewiseEPWM4AandEPWM4B
belongtoePWM4.
TheePWMmodulerepresentsonecompletePWMchannelcomposedoftwoPWMoutputs:EPWMxA
andEPWMxB.MultipleePWMmodulesareinstancedwithinadeviceasshowninFigure1-1.Each
ePWMinstanceisidenticalwithoneexception.Someinstancesincludeahardwareextensionthatallows
moreprecisecontrolofthePWMoutputs.Thisextensionisthehigh-resolutionpulsewidthmodulator
(HRPWM)andisdescribedintheTMS320x28xx,28xxxHigh-ResolutionPulseWidthModulator
(HRPWM)ReferenceGuide(SPRU924).Seethedevice-specificdatamanualtodeterminewhichePWM
instancesincludethisfeature.EachePWMmoduleisindicatedbyanumericalvaluestartingwith1.For
exampleePWM1isthefirstinstanceandePWM3isthe3rdinstanceinthesystemandePWMxindicates
anyinstance.
TheePWMmodulesarechainedtogetherviaaclocksynchronizationschemethatallowsthemtooperate
asasinglesystemwhenrequired.Additionally,thissynchronizationschemecanbeextendedtothe
captureperipheralmodules(eCAP).Thenumberofmodulesisdevice-dependentandbasedontarget
applicationneeds.Modulescanalsooperatestand-alone.
EachePWMmodulesupportsthefollowingfeatures:
•Dedicated16-bittime-basecounterwithperiodandfrequencycontrol
•TwoPWMoutputs(EPWMxAandEPWMxB)thatcanbeusedinthefollowingconfigurations::
–TwoindependentPWMoutputswithsingle-edgeoperation
–TwoindependentPWMoutputswithdual-edgesymmetricoperation
–OneindependentPWMoutputwithdual-edgeasymmetricoperation
•AsynchronousoverridecontrolofPWMsignalsthroughsoftware.
•Programmablephase-controlsupportforlagorleadoperationrelativetootherePWMmodules.
•Hardware-locked(synchronized)phaserelationshiponacycle-by-cyclebasis.
•Dead-bandgenerationwithindependentrisingandfallingedgedelaycontrol.
•Programmabletripzoneallocationofbothcycle-by-cycletripandone-shottriponfaultconditions.
•Atripconditioncanforceeitherhigh,low,orhigh-impedancestatelogiclevelsatPWMoutputs.
•AlleventscantriggerbothCPUinterruptsandADCstartofconversion(SOC)
•ProgrammableeventprescalingminimizesCPUoverheadoninterrupts.
•PWMchoppingbyhigh-frequencycarriersignal,usefulforpulsetransformergatedrives.
EachePWMmoduleisconnectedtotheinput/outputsignalsshowninFigure1-1.Thesignalsare
describedindetailinsubsequentsections.
14IntroductionSPRU791D–November2004–RevisedOctober2007
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