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7.4DSPSleepModeManagement
7.4.1DSPSleepModes
7.4.2DSPModuleClockON/OFF
7.4.2.1DSPModuleClockON
DSPSleepModeManagement
TheC64x+DSPsupportssleepmodemanagementtoreducepower:
•DSPclockcanbecompletelyshutoff
•C64x+Megamodulecanbeputinsleepmode
–C64x+CPUcanbeputinsleepmode
OntheDM643xDMP,sleepmodefortheDSPinternalmemories(L1P,L1D,L2)isnotsupported.
TheC64x+MegamoduleoftheDSPsubsystemincludesapower-downcontroller(PDC)thatcontrolsthe
power-downoftheC64x+Megamodulecomponents.RefertoSection2.4.2andtheTMS320C64x+DSP
MegamoduleReferenceGuide(SPRU871)formoredetailsonthePDC.
AsdiscussedinSection7.4.1,theC64x+Megamodulecanclockgateitsowncomponentstosavepower.
AdditionalpowersavingcanbeachievedbystoppingtheclocksourcetotheC64x+Megamoduleby
programmingthepowerandsleepcontroller(PSC)toplacetheC64x+MegamoduleinDisablestate.The
C64x+DSPcannotperformthisprogrammingtaskonitsown,becausetheC64x+DSPwillnotbeableto
completethePSCprogrammingsequenceiftheC64x+DSPclocksourceisgatedinthemiddleofthe
process.IfstoppingtheclocksourcetotheC64x+DSPisdesiredforadditionalpowersaving,anexternal
hostisresponsibleforprogrammingthePSC(forexample,viaHPI,PCIinterfaces)todisabletheC64x+
Megamodule.Similarly,inthatcasetheexternalhostisresponsibleforprogrammingthePSCtoenable
theC64x+Megamodule.
IntheclockEnablestate,theDSP’smoduleclockisenabledwhileDSPmoduleresetisde-asserted.This
isthestatefornormalDSPrun-time.DSPdefaultstoEnablestate,thereforethisDSPModuleClockON
processistypicallynotneeded.ThisprocessisonlyrequiredtowakeuptheDSPafteranexternalhost
putstheDSPinDisablestate(Section7.4.2.2).
•Host:EnableclockstotheDSP.
–WaitfortheGOSTAT[0]bitinPTSTATtoclearto0.Youmustwaitforthepowerdomaintofinish
anypreviouslyinitiatedtransitionsbeforeinitiatinganewtransition.
–SettheNEXTbitinMDCTL39to3htopreparetheDSPmoduleforanenabletransition.
–SettheGO[0]bitinPTCMDto1toinitiatethestatetransition.
–WaitfortheGOSTAT[0]bitinPTSTATtoclearto0.Thedomainisonlysafelyinthenewstate
aftertheGOSTAT[0]bitisclearedto0.
–WaitfortheSTATEbitinMDSTAT39tochangeto3h.Themoduleisonlysafelyinthenewstate
aftertheSTATEbitinMDSTAT39changestoreflectthenewstate.
•Host:WaketheDSP.
–Iftransitioningfromthedisablestate,triggeraDSPinterruptthathaspreviouslybeenconfiguredas
awake-upinterrupt.
Note:Thissteponlyappliesifyouaretransitioningfromthedisablestate.Ifpreviouslyinthe
disablestate,awake-upinterruptmustbetriggeredinordertowaketheDSP.Thisexample
assumesthattheDSPenabledthisinterruptbeforeenteringitsIDLEstate.Ifpreviouslyin
thesoftwareresetdisableorsynchronousresetstate,itisnotnecessarytowaketheDSP
becausethesestatesasserttheDSPmodulereset.SeeChapter10forinformationonthe
softwareresetdisableandsynchronousresetstates.SeetheTMS320C64x+DSP
MegamoduleReferenceGuide(SPRU871)formoreinformationonDSPinterrupts.
PowerManagement 80SPRU978E–March2008
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