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6.2.1PowerDomainStates
6.2.2ModuleStates
6.2.3DSPLocalReset
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PowerDomainandModuleTopology
Apowerdomaincanonlybeinoneoftwostates:ONorOFF,definedas:
•ON:powertothepowerdomainison.
•OFF:powertothepowerdomainisoff.
IntheDM646xDMSoC,thereisonlyonepowerdomain(AlwaysOn).TheAlwaysOnpowerdomainis
alwaysintheONstatewhenthechipispowered-on.
Amodulecanbeinoneoffourstates:Disable,Enable,SyncReset,orSwRstDisable,asdefinedbythe
STATEbitinthemodulestatusnregister(MDSTATn)inthePSC.Thesefourstatescorrespondto
combinationsofmoduleresetassertedordeassertedandmoduleclockonoroff,asshowninTable6-2.
Note:ModuleResetisdefinedtocompletelyresetagivenmodule,sothatallhardwarereturnsto
itsdefaultstate.SeeChapter10formoreinformationonmodulereset.
FormoreinformationontheDM646xDMSoCpowermanagement,seeChapter7.
Table6-2.ModuleStates
ModuleStateModuleResetModuleClockModuleStateDefinition
EnableDeassertedOnAmoduleintheEnablestatehasitsmoduleresetdeassertedandit
hasitsclockon.Thisisthenormalrun-timestateforagivenmodule.
DisableDeassertedOffAmoduleintheDisablestatehasitsmoduleresetdeassertedandit
hasitsclockoff.Thisstateistypicallyusedfordisablingamodule
clocktosavepower.TheDM646xDMSoCisdesignedinfullstatic
CMOS,sowhenyoustopamoduleclock,itretainsthemodule'sstate.
Whentheclockisrestarted,themoduleresumesoperatingfromthe
stoppingpoint.
SyncResetAssertedOnAmoduleintheSyncResetstatehasitsmoduleresetassertedandit
hasitsclockon.Afterinitialpower-on,mostmodulesareinthe
SyncRststatebydefault(seeTable6-1).Generally,softwareisnot
expectedtoinitiatethisstate.
SwRstDisableAssertedOffAmoduleintheSwResetDisablestatehasitsmoduleresetasserted
andithasitsclocksettooff.Generally,softwareisnotexpectedto
initiatethisstate.
Inadditiontomodulereset(asdescribedinSection6.2.2),theDSPCPUcanberesetusingaspecial
localreset.WhenDSPlocalresetisasserted,theDSP’sinternalmemories(L1P,L1D,andL2)arestill
accessible.ThelocalresetonlyresetstheDSPCPUcore,nottherestoftheDSPsubsystem,aswould
theDSPmodulereset.LocalresetisusefulwhentheDSPmoduleisintheEnablestateorintheDisable
state;sincemoduleresetisassertedintheSyncResetandSwRstDisablestates,andmoduleresettakes
precedenceoverlocalreset.TheARMuseslocalresettoresettheDSPtoinitiatetheDSPbootprocess.
SeeChapter10andChapter12formoreinformationonlocalreset,aswellasDSPboot.
TheproceduresforassertinganddeassertingDSPlocalresetare:
1.CleartheLRSTbitinthemodulecontrol1register(MDCTL1)inthePSCto0.ThisassertstheDSP
localreset.Bydefault,afterpower-onresetorhardreset,theDSPbootsource(DSPBOOT)pin
determinesthedefaultstateoftheLRSTbitinMDCTL1.SeeChapter10formoreinformationonthis
bootconfigurationpin.
2.SettheLRSTbitinMDCTL1to1.ThisdeassertstheDSPlocalreset.Afterresetisdeasserted,ifthe
DSPisintheEnablestate,theDSPimmediatelybeginscodeexecutionfromthebootaddress
programmedintheDSPbootaddressregister(DSPBOOTADDR)intheSystemModule.
SPRUEP9A–May2008PowerandSleepController(PSC)65
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