HT45F3W datasheet(107/167 Pages) HOLTEK

107 / 167 page

Rev. 1.50

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HT45F3W

R-Type Blood Pressure Meter Flash MCU

HT45F3W

R-Type Blood Pressure Meter Flash MCU

A/D Operation

TheSTARTbitintheADCRregisterisusedtostartandresettheA/Dconverter.Whenthe

microcontrollersetsthisbitfromlowtohighandthenlowagain,ananalogtodigitalconversion

cyclewillbeinitiated.WhentheSTARTbitisbroughtfromlowtohighbutnotlowagain,the

EOCBbitintheADCRregisterwillbesethighandtheanalogtodigitalconverterwillbereset.It

istheSTARTbitthatisusedtocontroltheoverallstartoperationoftheinternalanalogtodigital

converter.

TheEOCBbitintheADCRregisterisusedtoindicatewhentheanalogtodigitalconversionprocess

iscomplete.Thisbitwillbeautomaticallysetto“0”bythemicrocontrollerafteraconversioncycle

hasended.Inaddition,thecorrespondingA/Dinterruptrequestflagwillbesetintheinterrupt

controlregister,andiftheinterruptsareenabled,anappropriateinternalinterruptsignalwillbe

generated.ThisA/DinternalinterruptsignalwilldirecttheprogramflowtotheassociatedA/D

internalinterruptaddressforprocessing.IftheA/Dinternalinterruptisdisabled,themicrocontroller

canbeusedtopolltheEOCBbitintheADCRregistertocheckwhetherithasbeenclearedasan

alternativemethodofdetectingtheendofanA/Dconversioncycle.

TheclocksourcefortheA/Dconverter,whichoriginatesfromthesystemclockfSYS,canbechosen

tobeeitherfSYSorasubdividedversionoffSYSThedivisionratiovalueisdeterminedbythe

ADCK2~ADCK0bitsintheACSRregister.

Controllingthepoweron/offfunctionoftheA/Dconvertercircuitryisimplementedusingthe

ADOFFbitintheADCRregister.ThisbitmustbezerotopowerontheA/Dconverter.Whenthe

ADOFFbitisclearedtozerotopowerontheA/Dconverterinternalcircuitryacertaindelay,as

indicatedinthetimingdiagram,mustbeallowedbeforeanA/Dconversionisinitiated.Evenifno

pinsareselectedforuseasA/DinputsbyclearingthePCR3~PCR0bitsintheANCSRregisters,if

theADOFFbitiszerothensomepowerwillstillbeconsumed.Inpowerconsciousapplicationsit

isthereforerecommendedthattheADOFFissethightoreducepowerconsumptionwhentheA/D

converterfunctionisnotbeingused.

ThereferencevoltagesupplytotheA/DConvertercanbesuppliedfromeitherthepositivepower

supplypin,VDD,orfromanexternalreferencesourcessuppliedonpinVREF.Thedesiredselection

ismadeusingtheVREFSbit.AstheVREFpinispin-sharedwithotherfunctions,whentheVREFS

bitissethigh,theVREFpinfunctionwillbeselectedandtheotherpinfunctionswillbedisabled

automatically.

Conversion Accumulation Mode

EachsingleA/Dconversionoperationprovidesa12-bitwidedigitalconversionvalue.IftheACCM

bitiszerothenonlyasingleA/Dconversionprocesswilltakeplace.HoweveriftheACCMbit

issethighthentheA/Dconverterwillbeintheconversionaccumulationmode.Inthismode,

16repetitiveA/Dconversionoperationsaremadewitheachnewconvertedvaluebeingaddedto

thepreviousaccumulatedvalue.Afterthe16conversionvalues,eachof12-bitsinlength,have

completedandaddedtogether,aresulting16-bitwidedigitalvalueisobtainedandstoredinthetwo

A/Ddataregisters.Howeveritmustbenotedthat,althoughtheaccumulatedresultprovidesafull

16-bitvalue,onlythe13higherbits,16bitswillbevalid.WheninthismodetheEOCBbitwillbe

clearedtozeroafter16conversionoperationshavecompleted.

HT45F3W Datasheet(PDF) 107 Page - Holtek Semiconductor Inc

HT45F3W Datasheet(HTML) 107 Page - Holtek Semiconductor Inc

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