Holtek HT66F30 - Internal Low Speed Oscillator - LIRC; S�Pplementary Oscillators

Rev. 2.50 54 June 22, 2017 Rev. 2.50 55 June 22, 2017
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
LXT Oscillator Low Power Function
TheLXToscillatorcanfunctioninoneoftwomodes,theQuickStartModeandtheLowPower
Mode.ThemodeselectionisexecutedusingtheLXTLPbitintheTBCregister.
LXTLP Bit LXT Mode
0
Quick Start
1 Low-power
AfterpowerontheLXTLPbitwillbeautomaticallyclearedtozeroensuringthattheLXToscillator
isintheQuickStartoperatingmode.IntheQuickStartModetheLXToscillatorwillpowerup
andstabilisequickly.However,aftertheLXToscillatorhasfullypoweredupitcanbeplaced
intotheLow-powermodebysettingtheLXTLPbithigh.Theoscillatorwillcontinuetorunbut
withreducedcurrentconsumption,asthehighercurrentconsumptionisonlyrequiredduringthe
LXToscillatorstart-up.Inpowersensitiveapplications,suchasbatteryapplications,wherepower
consumptionmustbekepttoaminimum,itisthereforerecommendedthattheapplicationprogram
setstheLXTLPbithighabout2secondsafterpower-on.
Itshouldbenotedthat,nomatterwhatconditiontheLXTLPbitissetto,theLXToscillatorwill
alwaysfunctionnormally,theonlydifferenceisthatitwilltakemoretimetostartupifinthe
Low-powermode.
Internal Low Speed Oscillator – LIRC
TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis
selectedviacongurationoption.ItisafullyintegratedRCoscillatorwithatypicalfrequencyof
32kHzat5V,requiringnoexternalcomponentsforitsimplementation.Devicetrimmingduring
themanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareused
toensurethattheinuenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe
oscillationfrequencyareminimised.Asaresult,atapowersupplyof5Vandatatemperatureof
25˚Cdegrees,thexedoscillationfrequencyof32kHzwillhaveatolerancewithin10%.
Supplementary Oscillators
Thelowspeedoscillators,inadditiontoprovidingasystemclocksourcearealsousedtoprovide
aclocksourcetotwootherdevicefunctions.ThesearetheWatchdogTimerandtheTimeBase
Interrupts.