HT45F65 datasheet(57/231 Pages) HOLTEK

57 / 231 page

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HT45F65/HT45F66/HT45F67

Glucose Meter 8-Bit Flash MCU

Standby Current Considerations

AsthemainreasonforenteringtheSLEEPorIDLEModeistokeepthecurrentconsumptionofthe

devicetoaslowavalueaspossible,perhapsonlyintheorderofseveralmicro-ampsexceptinthe

IDLE1Mode,thereareotherconsiderationswhichmustalsobetakenintoaccountbythecircuit

designerifthepowerconsumptionistobeminimised.SpecialattentionmustbemadetotheI/Opins

onthedevice.Allhigh-impedanceinputpinsmustbeconnectedtoeitherafixedhighorlowlevelas

anyfloatinginputpinscouldcreateinternaloscillationsandresultinincreasedcurrentconsumption.

Thisalsoappliestothedevicewhichhasdifferentpackagetypes,astheremaybeunbonbedpins.

Thesemusteitherbesetupasoutputsorifsetupasinputsmusthavepull-highresistorsconnected.

Caremustalsobetakenwiththeloads,whichareconnectedtoI/Opins,whicharesetupasoutputs.

Theseshouldbeplacedinaconditioninwhichminimumcurrentisdrawnorconnectedonlyto

externalcircuitsthatdonotdrawcurrent,suchasotherCMOSinputs.Alsonotethatadditional

standbycurrentwillalsoberequirediftheconfigurationoptionshaveenabledtheLXTorLIRC

oscillator.

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.

EachpinonPortAcanbesetupusingthePAWUregistertopermitanegativetransitiononthepin

towake-upthesystem.WhenaPortApinwake-upoccurs,theprogramwillresumeexecutionat

theinstructionfollowingthe"HALT"instruction.Ifthesystemiswokenupbyaninterrupt,then

twopossiblesituationsmayoccur.Thefirstiswheretherelatedinterruptisdisabledortheinterrupt

isenabledbutthestackisfull,inwhichcasetheprogramwillresumeexecutionattheinstruction

followingthe"HALT"instruction.Inthissituation,theinterruptwhichwoke-upthedevicewillnot

beimmediatelyserviced,butwillratherbeservicedlaterwhentherelatedinterruptisfinallyenabled

orwhenastacklevelbecomesfree.Theothersituationiswheretherelatedinterruptisenabledand

thestackisnotfull,inwhichcasetheregularinterruptresponsetakesplace.Ifaninterruptrequest

flagissethighbeforeenteringtheSLEEPorIDLEMode,thewake-upfunctionoftherelated

interruptwillbedisabled.

HT45F65 Datasheet(PDF) 57 Page - Holtek Semiconductor Inc

HT45F65 Datasheet(HTML) 57 Page - Holtek Semiconductor Inc

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