HT67F488 datasheet(40/171 Pages) HOLTEK

40 / 171 page

Rev. 1.60

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

LXT Oscillator Low Power Function

TheLXToscillatorcanfunctioninoneoftwomodes,theQuickStartModeandtheLowPower

Mode.ThemodeselectionisexecutedusingtheLXTLPbitintheFSUBCregister.

FSUBC Register

Bit

�a�e

LXTLP

FSUB6

FSUB5

FSUB4

FSUB3

FSUB�

FSUB1

FSUB0

R/W

POR

Bit7

LXTLP:LXTLowPowerControl

0:QuickStartMode

1:LowPowerMode

Bit6~0

FSUB6~FSUB0:fSUBclocksourceselection

0101010:LIRC

1010101:LXT

Others:MCUreset

Afterpoweron,theLXTLPbitwillbeautomaticallyclearedtozeroensuringthattheLXToscillator

isintheQuickStartoperatingmode.IntheQuickStartModetheLXToscillatorwillpowerup

andstabilisequickly.However,aftertheLXToscillatorhasfullypoweredupitcanbeplaced

intotheLow-powermodebysettingtheLXTLPbithigh.Theoscillatorwillcontinuetorunbut

withreducedcurrentconsumption,asthehighercurrentconsumptionisonlyrequiredduringthe

LXToscillatorstart-up.Inpowersensitiveapplications,suchasbatteryapplications,wherepower

consumptionmustbekepttoaminimum,itisthereforerecommendedthattheapplicationprogram

setstheLXTLPbithighabout2secondsafterpower-on.

Itshouldbenotedthat,nomatterwhatconditiontheLXTLPbitissetto,theLXToscillatorwill

alwaysfunctionnormally,theonlydifferenceisthatitwilltakemoretimetostartupifintheLow-

powermode.

Internal 32kHz Oscillator – LIRC

TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis

selectedviatheFSUBCregister.ItisafullyintegratedRCoscillatorwithatypicalfrequencyof

32kHzat5V,requiringnoexternalcomponentsforitsimplementation.Devicetrimmingduring

themanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareused

toensurethattheinfluenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe

oscillationfrequencyareminimised.Asaresult,atapowersupplyof5Vandatatemperatureof

25°Cdegrees,thefixedoscillationfrequencyof32kHzwillhaveatolerancewithin10%.

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