HT45F65 datasheet(48/231 Pages) HOLTEK

48 / 231 page

Rev. 1.60

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HT45F65/HT45F66/HT45F67

Glucose Meter 8-Bit Flash MCU

Internal 32kHz Oscillator – LIRC

TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis

selectedviaconfigurationoption.ItisafullyintegratedRCoscillatorwithatypicalfrequencyof

32kHzat5V,requiringnoexternalcomponentsforitsimplementation.Devicetrimmingduring

themanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareused

toensurethattheinfluenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe

oscillationfrequencyareminimised.Asaresult,atapowersupplyof5Vandatatemperatureof

25°Cdegrees,thefixedoscillationfrequencyof32kHzwillhaveatolerancewithin10%.

Supplementary Oscillators

Thelowspeedoscillators,inadditiontoprovidingasystemclocksourcearealsousedtoprovidea

clocksourcetothreeotherdevicefunctions.ThesearetheWatchdogTimer,theLCDdriverandthe

TimeBaseInterrupts.

Operating Modes and System Clocks

Presentdayapplicationsrequirethattheirmicrocontrollershavehighperformancebutoftenstill

demandthattheyconsumeaslittlepoweraspossible,conflictingrequirementsthatareespecially

trueinbatterypoweredportableapplications.Thefastclocksrequiredforhighperformancewill

bytheirnatureincreasecurrentconsumptionandofcoursevice-versa,lowerspeedclocksreduce

currentconsumption.AsHoltekhasprovidedthesedeviceswithbothhighandlowspeedclock

sourcesandthemeanstoswitchbetweenthemdynamically,theusercanoptimisetheoperationof

theirmicrocontrollertoachievethebestperformance/powerratio.

System Clocks

ThedeviceshavemanydifferentclocksourcesforboththeCPUandperipheralfunctionoperation.

Byprovidingtheuserwithawiderangeofclockoptionsusingconfigurationoptionsandregister

programming,aclocksystemcanbeconfiguredtoobtainmaximumapplicationperformance.

Themainsystemclock,cancomefromeitherahighfrequencyfHorlowfrequencyfLsource,andis

selectedusingtheHLCLKbitandCKS2~CKS0bitsintheSMOD0register.Thehighspeedsystem

clockcanbesourcedfromeitheranHXT,ERCorHIRCoscillator,selectedviaaconfiguration

option.ThelowspeedsystemclocksourcecanbesourcedfrominternalclockfL.IffLisselected

thenitcanbesourcedbyeithertheLXTorLIRCoscillator,selectedviaaconfigurationoption.

Theotherchoice,whichisadividedversionofthehighspeedsystemoscillatorhasarangeof

fH/2~fH/64.

Therearetwoadditionalinternalclocksfortheperipheralcircuits,thesubstituteclock,fSUB,and

theTimeBaseclock,fTBC.EachoftheseinternalclocksissourcedbyeithertheLXTorLIRC

oscillators,selectedviaconfigurationoptions.ThefSUBclockisusedtoprovideasubstituteclockfor

themicrocontrollerjustafterawake-uphasoccurredtoenablefasterwake-uptimes.

HT45F65 Datasheet(PDF) 48 Page - Holtek Semiconductor Inc

HT45F65 Datasheet(HTML) 48 Page - Holtek Semiconductor Inc

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