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전자부품 데이터시트 검색엔진 |
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전자부품 데이터시트 검색엔진 |
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HT66F25D 데이터시트(PDF) 49 Page - Holtek Semiconductor Inc |
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HT66F25D 데이터시트(HTML) 49 Page - Holtek Semiconductor Inc |
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49 / 177 page  A/D Flash Type 8-bit MCU with EEPROM HT66F24D/HT66F25D Rev. 1.00 48 ���� ��� �01� Rev. 1.00 49 ���� ��� �01� Standby Current Considerations AsthemainreasonforenteringtheSLEEPorIDLEModeistokeepthecurrentconsumptionofthe devicetoaslowavalueaspossible,perhapsonlyintheorderofseveralmicro-ampsexceptinthe IDLE1Mode,thereareotherconsiderationswhichmustalsobetakenintoaccountbythecircuit designerifthepowerconsumptionistobeminimised.SpecialattentionmustbemadetotheI/Opins onthedevice.Allhigh-impedanceinputpinsmustbeconnectedtoeitherafixedhighorlowlevelas anyfloatinginputpinscouldcreateinternaloscillationsandresultinincreasedcurrentconsumption. Thisalsoappliestodeviceswhichhavedifferentpackagetypes,astheremaybeunbonbedpins. Thesemusteitherbesetupasoutputsorifsetupasinputsmusthavepull-highresistorsconnected. Caremustalsobetakenwiththeloads,whichareconnectedtoI/Opins,whicharesetupasoutputs. Theseshouldbeplacedinaconditioninwhichminimumcurrentisdrawnorconnectedonlyto externalcircuitsthatdonotdrawcurrent,suchasotherCMOSinputs.Alsonotethatadditional standbycurrentwillalsoberequirediftheconfigurationoptionshaveenabledtheLXTortheLIRC oscillator. IntheIDLE1Modethesystemoscillatorison,ifthesystemoscillatorisfromthehighspeedsystem oscillator,theadditionalstandbycurrentwillalsobeperhapsintheorderofseveralhundredmicro-amps. Wake-up AfterthesystementerstheSLEEPorIDLEMode,itcanbewokenupfromoneofvarioussources listedasfollows: • AnexternalfallingedgeonPortA • Asysteminterrupt • AWDToverflow IfthedeviceiswokenupbyaWDToverflow,aWatchdogTimerresetwillbeinitiated.IfaWDT time-outoccurs,itwillsetTOflagandcauseawake-upthatonlyresetstheProgramCounterand StackPointer,theotherflagsremainintheiroriginalstatus. EachpinonPortAcanbesetupusingthePAWUregistertopermitanegativetransitiononthepin towake-upthesystem.WhenaPortApinwake-upoccurs,theprogramwillresumeexecutionat theinstructionfollowingtheHALTinstruction.Ifthesystemiswokenupbyaninterrupt,thentwo possiblesituationsmayoccur.Thefirstiswheretherelatedinterruptisdisabledortheinterrupt isenabledbutthestackisfull,inwhichcasetheprogramwillresumeexecutionattheinstruction followingtheHALTinstruction.Inthissituation,theinterruptwhichwoke-upthedevicewillnotbe immediatelyserviced,butwillratherbeservicedlaterwhentherelatedinterruptisfinallyenabledor whenastacklevelbecomesfree.Theothersituationiswheretherelatedinterruptisenabledandthe stackisnotfull,inwhichcasetheregularinterruptresponsetakesplace.Ifaninterruptrequestflag issethighbeforeenteringtheSLEEPorIDLEMode,thewake-upfunctionoftherelatedinterrupt willbedisabled. Programming Considerations TheHXTandLXToscillatorsbothusethesameSSTcounter.Forexample,ifthesystemiswoken upfromtheSLEEP0ModeandboththeHXTandLXToscillatorsneedtostart-upfromanoffstate. TheLXToscillatorusestheSSTcounterafterHXToscillatorhasfinisheditsSSTperiod. IfthedeviceiswokenupfromtheSLEEP0ModetotheNORMALMode,thehighspeedsystem oscillatorneedsanSSTperiod.ThedevicewillexecutefirstinstructionaftertheHTObitissetto1. Atthistime,theLXToscillatormaynotbestabilityiffSUBisfromLXToscillator.Thesamesituation occursinthepower-onstate.TheLXToscillatorisnotreadyyetwhenthefirstinstructionisexecuted. |
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