HT45F3W datasheet(148/167 Pages) HOLTEK

148 / 167 page

Rev. 1.50

148

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Rev. 1.50

149

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HT45F3W

R-Type Blood Pressure Meter Flash MCU

HT45F3W

R-Type Blood Pressure Meter Flash MCU

Programming Considerations

CertainprecautionsmustbetakenwhenprogrammingtheLCD.Oneoftheseistoensurethatthe

DisplayMemoryisproperlyinitialisedafterthemicrocontrollerispoweredon.LiketheGeneral

PurposeDataMemory,thecontentsoftheDisplayMemoryareinanunknownconditionafter

power-on.AsthecontentsoftheDisplayMemorywillbemappedintotheactualdisplay,itis

importanttoinitialisethismemoryareaintoaknownconditionsoonafterapplyingpowertoobtain

aproperdisplaypattern.

ConsiderationmustalsobegiventothecapacitiveloadoftheactualLCDusedintheapplication.

AstheloadpresentedtothemicrocontrollerbyLCDpixelscanbegenerallymodeledasmainly

capacitiveinnature,itisimportantthatthisisnotexcessive,apointthatisparticularlytrueinthe

caseoftheCOMlineswhichmaybeconnectedtomanyLCDpixels.Theaccompanyingdiagram

depictstheequivalentcircuitoftheLCD.

One additional consideration that must be taken into account is what happens when the

microcontrollerentersaPowerDowncondition.TheLCDENcontrolbitintheLEDCTRL

registerpermitsthedisplaytobepoweredofftoreducepowerconsumption.Ifthisbitiszero,the

drivingsignalstothedisplaywillcease,producingablankdisplaypatternbutreducinganypower

consumptionassociatedwiththeLCD.

AfterPower-on,notethatastheLCDENbitwillbeclearedtozero,thedisplayfunctionwillbe

disabled.Theaccompanyingtimingdiagramsdepictthedisplaydriversignalsgeneratedbythe

microcontrollerforvariousvaluesofdutyandbias.Thehugerangeofvariouspermutationsdoes

notpermitalltypestobedisplayedhere.

CO M0

CO M1

CO M2

CO Mn

SE G0

SEG 1S EG 2

SEG n

LCD Panel Equivalent Circuit

HT45F3W Datasheet(PDF) 148 Page - Holtek Semiconductor Inc