HT45F12 datasheet(44/104 Pages) HOLTEK

44 / 104 page

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HT45F12

8-Bit Flash MCU with Op Amps & Comparators

HT45F12

8-Bit Flash MCU with Op Amps & Comparators

Entering the IDLE1 Mode

ThereisonlyonewayforthedevicetoentertheIDLE1Modeandthatistoexecutethe“HALT”

instructionintheapplicationprogramwiththeIDLENbitinSYSMODregisterequalto“1”andthe

FSYSONbitinCTRLregisterequalto“1”.Whenthisinstructionisexecutedundertheconditions

describedabove,thefollowingwilloccur:

• ThesystemclockandTimeBaseclockandfSUBclockwillbeonandtheapplicationprogramwill

stopatthe“HALT”instruction

• TheDataMemorycontentsandregisterswillmaintaintheirpresentcondition.

• TheWDTwillbeclearedandresumecountingiftheWDTisenabledregardlessoftheWDT

clocksourcewhichoriginatesfromthefLclock

• TheI/Oportswillmaintaintheirpresentconditions.

• Inthestatusregister,thePowerDownflag,PDF,willbesetandtheWatchdogtime-outflag,TO,

willbecleared.

Standby Current Considerations

AsthemainreasonforenteringtheSLEEPorIDLEModeistokeepthecurrentconsumptionofthe

devicetoaslowavalueaspossible,perhapsonlyintheorderofseveralmicro-ampsexceptinthe

IDLE1Mode,thereareotherconsiderationswhichmustalsobetakenintoaccountbythecircuit

designerifthepowerconsumptionistobeminimised.SpecialattentionmustbemadetotheI/Opins

onthedevice.Allhigh-impedanceinputpinsmustbeconnectedtoeitherafixedhighorlowlevelas

anyfloatinginputpinscouldcreateinternaloscillationsandresultinincreasedcurrentconsumption.

Thisalsoappliestodevicewhichhasdifferentpackagetypes,astheremaybeunbondedpins.These

musteitherbesetupasoutputsorifsetupasinputsmusthavepull-highresistorsconnected.

Caremustalsobetakenwiththeloads,whichareconnectedtoI/Opins,whicharesetupasoutputs.

Theseshouldbeplacedinaconditioninwhichminimumcurrentisdrawnorconnectedonlyto

externalcircuitsthatdonotdrawcurrent,suchasotherCMOSinputs.Alsonotethatadditional

standbycurrentwillalsoberequirediftheconfigurationoptionshaveenabledtheLIRCoscillator.

IntheIDLE1Modethesystemoscillatorison,ifthesystemoscillatorisfromthehighspeedsystem

oscillator,theadditionalstandbycurrentwillalsobeperhapsintheorderofseveralhundredmicro-

amps.

Wake-up

AfterthesystementerstheSLEEPorIDLEMode,itcanbewokenupfromoneofvarioussources

listedasfollows:

• Anexternalreset

• AnexternalfallingedgeonPortA

• Asysteminterrupt

• AWDToverflow

Ifthesystemiswokenupbyanexternalreset,thedevicewillexperienceafullsystemreset,

however,ifthedeviceiswokenupbyaWDToverflow,aWatchdogTimerresetwillbeinitiated.

Althoughbothofthesewake-upmethodswillinitiatearesetoperation,theactualsourceofthe

wake-upcanbedeterminedbyexaminingtheTOandPDFflags.ThePDFflagisclearedbya

systempower-uporexecutingtheclearWatchdogTimerinstructionsandissetwhenexecutingthe

“HALT”instruction.TheTOflagissetifaWDTtime-outoccurs,andcausesawake-upthatonly

resetstheProgramCounterandStackPointer,theotherflagsremainintheiroriginalstatus.

HT45F12 Datasheet(PDF) 44 Page - Holtek Semiconductor Inc

HT45F12 Datasheet(HTML) 44 Page - Holtek Semiconductor Inc

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