HT45F3W datasheet(110/167 Pages) HOLTEK

110 / 167 page

Rev. 1.50

110

De�e��e� 01� �01�

Rev. 1.50

111

De�e��e� 01� �01�

HT45F3W

R-Type Blood Pressure Meter Flash MCU

HT45F3W

R-Type Blood Pressure Meter Flash MCU

Theaccompanyingdiagramshowsgraphicallythevariousstagesinvolvedinananalogtodigital

conversionprocessanditsassociatedtiming.AfteranA/Dconversionprocesshasbeeninitiated

bytheapplicationprogram,themicrocontrollerinternalhardwarewillbegintocarryoutthe

conversion,duringwhichtimetheprogramcancontinuewithotherfunctions.Thetimetakenforthe

A/Dconversionis16tADwheretADisequaltotheA/Dclockperiod.

NotethatwhenintheConversionAccumulationMode,16conversioncycleswillberequiredbefore

theEOCBbitisclearedtozero.

A/D Single Conversion Mode Timing

Programming Considerations

DuringmicrocontrolleroperationswheretheA/Dconverterisnotbeingused,theA/Dinternal

circuitrycanbeswitchedofftoreducepowerconsumption,bysettingbitADOFFhighintheADCR

ofwhatanalogvoltageisappliedtotheirinputlines.IftheA/Dconverterinputlinesareusedas

normalI/Os,thencaremustbetakenasiftheinputvoltageisnotatavalidlogiclevel,thenthismay

leadtosomeincreaseinpowerconsumption.

Thepower-onresetconditionoftheA/Dconvertercontrolregisterswillensurethattheshared

functionpinsaresetupasA/Dconverterinputs.IfanyoftheA/Dconverterinputpinsaretobeused

forfunctions,thentheA/DconvertercontrolregisterbitsmustbeproperlysetuptodisabletheA/D

inputconfiguration.

A/D Transfer Function

Asthedevicecontainsa12-bitA/Dconverter,itsfull-scaleconverteddigitisedvalueisequalto

FFFH.Sincethefull-scaleanaloginputvalueisequaltotheVDDorVREFvoltage,thisgivesasingle

bitanaloginputvalueofVDDorVREFdividedby4096.

1LSB=(VDDorVREF)÷4096

TheA/DConverterinputvoltagevaluecanbecalculatedusingthefollowingequation:

A/Dinputvoltage=A/Doutputdigitalvalue×(VDDorVREF)÷4096

HT45F3W Datasheet(PDF) 110 Page - Holtek Semiconductor Inc