HT56R656 datasheet(49/145 Pages) HOLTEK

49 / 145 page

Rev. 1.30

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Rev. 1.30

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HT56R62/HT56R65

HT56R642/HT56R644/HT56R654/HT56R656

TinyPowerTM A/D Type with LCD 8-Bit OTP MCU

HT56R62/HT56R65

HT56R642/HT56R644/HT56R654/HT56R656

TinyPowerTM A/D Type with LCD 8-Bit OTP MCU

LCD Reset Function

TheLCDhasaninternalresetfunctionthatisanORfunctionoftheinvertedLCDENbitinthe

LCDCTRLregisterandtheSleepfunction.TheLCDresetsignalisactivehigh.TheLCDENsignal

istheinverseoftheLCDENbitintheLCDCTRLregister.

ResetLCD=(SleepModeANDLCDEN)ORLCDEN.

LCDEN=0andLCDEN=1mustbeenabledtoactivatetheLCDCTRLregisterfunction.

LCDEN

Sleep Mode

Reset LCD

Off

√

Off

√

LCD Reset Function

Clock Source

TheLCDclocksourceistheinternalclocksignal,fSUB,dividedby8,usinganinternaldivider

circuit.ThefSUBinternalclockissuppliedbyeithertheinternal32K_INToscillatorortheexternal

32768Hzoscillator,thechoiceofwhichisdeterminedbyaconfigurationoption.ForproperLCD

operation,thisarrangementisprovidedtogenerateanidealLCDclocksourcefrequencyof4kHz.

fSUB Clock Source

LCD Clock Frequency

Internal 32K_INT Osc.

4kHz

External 32768Hz Osc.

4kHz

LCD Clock Source

LCD Driver Output

WhentheLEDSELbitintheLEDCTRLregisterisclearedtozero,theCOMandSEGlineswillbe

setupasLCDdriverpinstodrivetheLCDdisplay.

ThenumberofCOMandSEGoutputssuppliedbytheLCDdriver,aswellasitsbiasingandduty

selections,aredependentuponhowtheLCDcontrolbitsareprogrammed.TheBiasType,whether

CorRtypeisselectedusingaconfigurationoption.

IftheC-typeofbiasisusedwhenaninternalchargepumpwillbeenabled.NotethattheC-typebias

isnotavailableonthe52-pinQFPpackagetype.

ThenatureofLiquidCrystalDisplaysrequirethatonlyACvoltagescanbeappliedtotheirpixels

astheapplicationofDCvoltagestoLCDpixelsmaycausepermanentdamage.Forthisreason

therelativecontrastofanLCDdisplayiscontrolledbytheactualRMSvoltageappliedtoeach

pixel,whichisequaltotheRMSvalueofthevoltageontheCOMpinminusthevoltageapplied

totheSEGpin.ThisdifferentialRMSvoltagemustbegreaterthantheLCDsaturationvoltage

forthepixeltobeonandlessthanthethresholdvoltageforthepixeltobeoff.Therequirement

tolimittheDCvoltagetozeroandtocontrolasmanypixelsaspossiblewithaminimumnumber

ofconnections,requiresthatbothatimeandamplitudesignalisgeneratedandappliedtothe

applicationLCD.ThesetimeandamplitudevaryingsignalsareautomaticallygeneratedbytheLCD

drivercircuitsinthemicrocontroller.Whatisknownasthedutydeterminesthenumberofcommon

linesused,whicharealsoknownasbackplanesorCOMs.Theduty,whichischosenbyacontrol

bittohaveavalueof1/2,1/3,1/4etcandwhichequatestoaCOMnumberof2,3,4etc,therefore

definesthenumberoftimedivisionswithineachLCDsignalframe.Twotypesofsignalgeneration

arealsoprovided,knownasTypeAandTypeB,therequiredtypeisselectedviatheTYPEbitin

theLCDCTRLregister.TypeBofferslowerfrequencysignals,howeverlowerfrequenciesmay

introduceflickeringandinfluencedisplayclarity.

HT56R656 Datasheet(PDF) 49 Page - Holtek Semiconductor Inc

HT56R656 Datasheet(HTML) 49 Page - Holtek Semiconductor Inc

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