HT45F3W datasheet(50/167 Pages) HOLTEK

50 / 167 page

Rev. 1.50

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Rev. 1.50

De�e��e� 01� �01�

HT45F3W

R-Type Blood Pressure Meter Flash MCU

HT45F3W

R-Type Blood Pressure Meter Flash MCU

Operating Modes and System Clocks

Presentdayapplicationsrequirethattheirmicrocontrollershavehighperformancebutoftenstill

demandthattheyconsumeaslittlepoweraspossible,conflictingrequirementsthatareespecially

trueinbatterypoweredportableapplications.Thefastclocksrequiredforhighperformancewill

bytheirnatureincreasecurrentconsumptionandofcoursevice-versa,lowerspeedclocksreduce

currentconsumption.AsHoltekhasprovidedthedevicewithbothhighandlowspeedclocksources

andthemeanstoswitchbetweenthemdynamically,theusercanoptimisetheoperationoftheir

microcontrollertoachievethebestperformance/powerratio.

System Clocks

ThedevicehasmanydifferentclocksourcesforboththeCPUandperipheralfunctionoperation.

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.

HT45F3W Datasheet(PDF) 50 Page - Holtek Semiconductor Inc