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HT45F23A Datasheet(PDF) 49 Page - Holtek Semiconductor Inc |
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HT45F23A Datasheet(HTML) 49 Page - Holtek Semiconductor Inc |
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49 / 148 page  Rev. 1.00 48 ���� 0�� �01� Rev. 1.00 49 ���� 0�� �01� HT45F23A 8-Bit Flash MCU with Op Amps & Comparators HT45F23A 8-Bit Flash MCU with Op Amps & Comparators Wake-up AfterthesystementerstheSLEEPorIDLEMode,itcanbewokenupfromoneofvarioussources listedasfollows: • Anexternalreset • AnexternalfallingedgeonPortA • Asysteminterrupt • AWDToverflow Ifthesystemiswokenupbyanexternalreset,thedevicewillexperienceafullsystemreset, however,ifthedeviceiswokenupbyaWDToverflow,aWatchdogTimerresetwillbeinitiated. Althoughbothofthesewake-upmethodswillinitiatearesetoperation,theactualsourceofthe wake-upcanbedeterminedbyexaminingtheTOandPDFflags.ThePDFflagisclearedbya systempower-uporexecutingtheclearWatchdogTimerinstructionsandissetwhenexecuting the"HALT"instruction.TheTOflagissetifaWDTtime-outoccurs,andcausesawake-upthatonly resetstheProgramCounterandStackPointer,theotherflagsremainintheiroriginalstatus. EachpinonPortAcanbesetupusingthePAWUregistertopermitanegativetransitiononthepin towake-upthesystem.WhenaPortApinwake-upoccurs,theprogramwillresumeexecutionat theinstructionfollowingthe"HALT"instruction.Ifthesystemiswokenupbyaninterrupt,then twopossiblesituationsmayoccur.Thefirstiswheretherelatedinterruptisdisabledortheinterrupt isenabledbutthestackisfull,inwhichcasetheprogramwillresumeexecutionattheinstruction followingthe"HALT"instruction.Inthissituation,theinterruptwhichwoke-upthedevicewillnotbe immediatelyserviced,butwillratherbeservicedlaterwhentherelatedinterruptisfinallyenabledor whenastacklevelbecomesfree.Theothersituationiswheretherelatedinterruptisenabledandthe stackisnotfull,inwhichcasetheregularinterruptresponsetakesplace.Ifaninterruptrequestflagis sethighbeforeenteringtheSLEEPorIDLEMode,thewake-upfunctionoftherelatedinterruptwill bedisabled. Programming Considerations TheHXTandLXToscillatorsbothusethesameSSTcounter.Forexample,ifthesystemiswoken upfromtheSLEEP0ModeandboththeHXTandLXToscillatorsneedtostart-upfromanoffstate. TheLXToscillatorusestheSSTcounterafterHXToscillatorhasfinisheditsSSTperiod. • IfthedeviceiswokenupfromtheSLEEP0ModetotheNORMALMode,thehighspeedsystem oscillatorneedsanSSTperiod.ThedevicewillexecutefirstinstructionafterHTOis"1".At thistime,theLXToscillatormaynotbestabilityiffSUBisfromLXToscillator.Thesamesituation occursinthepower-onstate.TheLXToscillatorisnotreadyyetwhenthefirstinstructionis executed. • IfthedeviceiswokenupfromtheSLEEP1ModetoNORMALMode,andthesystemclock sourceisfromHXToscillatorandFSTENis"1",thesystemclockcanbeswitchedtotheLXTor LIRCoscillatorafterwakeup. • Thereareperipheralfunctions,suchasWDT,TMsandSIM,forwhichthef SYS isused.Ifthe systemclocksourceisswitchedfromfHtofL,theclocksourcetotheperipheralfunctions mentionedabovewillchangeaccordingly. • Theon/offconditionoffSUBandf S dependsuponwhethertheWDTisenabledordisabledasthe WDTclocksourceisselectedfromf SUB . |
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