HT45F65 datasheet(144/231 Pages) HOLTEK

144 / 231 page

Rev. 1.60

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HT45F65/HT45F66/HT45F67

Glucose Meter 8-Bit Flash MCU

A/D Operation

TheSTARTbitintheADCR0registerisusedtostartandresettheA/Dconverter.Whenthe

microcontrollersetsthisbitfromlowtohighandthenlowagain,ananalogtodigitalconversion

cyclewillbeinitiated.WhentheSTARTbitisbroughtfromlowtohighbutnotlowagain,the

EOCBbitintheADCR0registerwillbesethighandtheanalogtodigitalconverterwillbereset.

ItistheSTARTbitthatisusedtocontroltheoverallstartoperationoftheinternalanalogtodigital

converter.

TheEOCBbitintheADCR0registerisusedtoindicatewhentheanalogtodigitalconversion

processiscomplete.Thisbitwillbeautomaticallysetto"0"bythemicrocontrolleraftera

conversioncyclehasended.Inaddition,thecorrespondingA/Dinterruptrequestflagwillbeset

intheinterruptcontrolregister,andiftheinterruptsareenabled,anappropriateinternalinterrupt

signalwillbegenerated.ThisA/Dinternalinterruptsignalwilldirecttheprogramflowtothe

associatedA/Dinternalinterruptaddressforprocessing.IftheA/Dinternalinterruptisdisabled,

themicrocontrollercanbeusedtopolltheEOCBbitintheADCR0registertocheckwhetherithas

beenclearedasanalternativemethodofdetectingtheendofanA/Dconversioncycle.

TheclocksourcefortheA/Dconverter,whichoriginatesfromthesystemclockfSYS,canbechosen

tobeeitherfSYSorasubdividedversionoffSYSThedivisionratiovalueisdeterminedbythe

ADCK2~ADCK0bitsintheADCR1register.

Controllingthepoweron/offfunctionoftheA/Dconvertercircuitryisimplementedusingthe

ADOFFbitintheADCR0register.ThisbitmustbezerotopowerontheA/Dconverter.Whenthe

ADOFFbitisclearedtozerotopowerontheA/Dconverterinternalcircuitryacertaindelay,as

indicatedinthetimingdiagram,mustbeallowedbeforeanA/Dconversionisinitiated.Evenifno

pinsareselectedforuse,iftheADOFFbitiszerothensomepowerwillstillbeconsumed.Inpower

consciousapplicationsitisthereforerecommendedthattheADOFFissethightoreducepower

consumptionwhentheA/Dconverterfunctionisnotbeingused.

ThepositivereferencevoltagesupplytotheA/DConvertercanbesuppliedfromeitherthepositive

powersupplypin,AVDD,orfromanexternalreferencesourcessuppliedonpinADVRHorfrom

bandgapoutput.ThedesiredselectionismadeusingtheVPRS[1:0]bit.

ThenegativereferencevoltagesupplytotheA/DConvertercanbesuppliedfromeithertheground

powersupplypin,AVSS,orfromanexternalreferencesourcessuppliedonpinADVRLorfrom

DACoutput.ThedesiredselectionismadeusingtheVNRS[1:0]bit.

TheADVRHandADVRLpinsarepin-sharedwithotherfunctions.

HT45F65 Datasheet(PDF) 144 Page - Holtek Semiconductor Inc