HT45FM2C datasheet(37/171 Pages) HOLTEK

37 / 171 page

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HT45FM2C

Brushless DC Motor Flash Type 8-Bit MCU

HT45FM2C

Brushless DC Motor Flash Type 8-Bit MCU

Preliminar�

Operating Modes and System Clocks

Presentdayapplicationsrequirethattheirmicrocontrollershavehighperformancebutoftenstill

demandthattheyconsumeaslittlepoweraspossible,conflictingrequirementsthatareespecially

trueinbatterypoweredportableapplications.Thefastclocksrequiredforhighperformancewill

bytheirnatureincreasecurrentconsumptionandofcourseviceversa,lowerspeedclocksreduce

currentconsumption.AsHoltekhasprovidedthisdevicewithbothhighandlowspeedclock

sourcesandthemeanstoswitchbetweenthemdynamically,theusercanoptimisetheoperationof

theirmicrocontrollertoachievethebestperformance/powerratio.

System Clocks

ThedevicehasmanydifferentclocksourcesforboththeCPUandperipheralfunctionoperation.

Byprovidingtheuserwithawiderangeofclockoptionsusingconfigurationoptionsandregister

programming,aclocksystemcanbeconfiguredtoobtainmaximumapplicationperformance.

Themainsystemclock,cancomefromeitherahighfrequency,fH,orlowfrequency,fL,source,and

isselectedusingtheHLCLKbitandCKS2~CKS0bitsintheSMODregister.Thehighspeedsystem

clockcanbesourcedfromHIRCoscillator.Thelowspeedsystemclocksourcecanbesourcedfrom

internalclockfL. If fLisselectedthenitcanbesourcedbytheLIRCoscillator.Theotherchoice,

whichisadividedversionofthehighspeedsystemoscillatorhasarangeoffH/2~fH/64.

Therearetwoadditionalinternalclocksfortheperipheralcircuits,thesubstituteclock,fSUB,and

theTimeBaseclock,fTBC.EachoftheseinternalclocksissourcedbytheLIRCoscillator.ThefSUB

clockisusedtoprovideasubstituteclockforthemicrocontrollerjustafterawake-uphasoccurred

toenablefasterwake-uptimes.

HT45FM2C Datasheet(PDF) 37 Page - Holtek Semiconductor Inc