HT45F77 datasheet(111/203 Pages) HOLTEK

111 / 203 page

Rev. 1.20

110

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Rev. 1.20

111

De�e��e� 1�� 201�

HT45F77

Body Fat Scale Flash MCU

HT45F77

Body Fat Scale Flash MCU

TheclocksourcefortheA/Dconvertershouldbetypicallyfixedatavalueof4.8MHz,which

originatesfromthesystemclockfSYS,andcanbechosentobeeitherfSYSorasubdividedversion

offSYS.ThedivisionratiovalueisdeterminedbytheADCK4~ADCK0bitsintheADCSregisterto

obtaina4.8MHzclocksourcefortheADC.

ThedifferentialreferencevoltagesupplytotheA/DConvertercanbesuppliedfromeitherthe

internalpowersupplypins,VCMandAVSS,orfromanexternalreferencesourcesuppliedonpins,

VREFPandVREFN.ThedesiredselectionismadeusingtheVREFSbitintheADCR0register.

Summary of A/D Conversion Steps

ThefollowingsummarisestheindividualstepsthatshouldbeexecutedinordertoimplementanA/D

conversionprocess.

• Step1

EnablepowerLDO,VCMforPGAandADC.

• Step2

SelectPGA,ADCandVREFgainbyPGAC0register.

• Step3

SelectPGAsettingforinputpinsconnectionandVCMoptionbyPGAC1register.

• Step4

Select the requiredA/D conversion clock 4.8MHz by correctly programming bits

ADCK4~ADCK0intheADCSregister.

• Step5

Selectoutputdatarate.

• Step6

SelectwhichchannelistobeconnectedtotheinternalPGAbycorrectlyprogrammingthe

CHSP2~CHSP0andCHSN2~CHSN0bitswhicharealsocontainedinthePGACSregister.

• Step7

ReleasepowerdownmodeandsleepmodebyADOFFandADSLPbitsinADCR0register.

• Step8

ResettheA/DbysettingtheADRSTtohighintheADCR0registerandclearingthisbittozero

toreleaseresetstatus.

• Step9

Iftheinterruptsaretobeused,theinterruptcontrolregistersmustbecorrectlyconfiguredto

ensuretheA/Dconverterinterruptfunctionisactive.Themasterinterruptcontrolbit,EMI,and

theA/Dconverterinterruptbit,ADE,mustbothbesethightodothis.

• Step10

Tocheckwhentheanalogtodigitalconversionprocessiscomplete,theEOCbitintheADCR1

registercanbepolled.Theconversionprocessiscompletewhenthisbitgoeslow.Whenthis

occurstheA/DdataregistersADRL,ADRMandADRHcanbereadtoobtaintheconversion

value.Asanalternativemethod,iftheinterruptsareenabledandthestackisnotfull,theprogram

canwaitforanA/Dinterrupttooccur.

Note:Whencheckingfortheendoftheconversionprocess,ifthemethodofpollingtheEOCbitin

theADCR1registerisused,theinterruptenablestepabovecanbeomitted.

HT45F77 Datasheet(PDF) 111 Page - Holtek Semiconductor Inc

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