HT66F005 datasheet(42/109 Pages) HOLTEK

42 / 109 page

Rev. 1.30

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Rev. 1.30

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HT66F005/HT66F006

Cost-Effective A/D Flash MCU with EEPROM

HT66F005/HT66F006

Cost-Effective A/D Flash MCU with EEPROM

Programming Considerations

ThehighspeedandlowspeedoscillatorsbothusethesameSSTcounter.

• IfthesedevicesarewokenupfromtheSLEEP1ModetoNORMALMode,andthesystemclock

sourceisfromHXToscillatorandFSTENis“1”,thesystemclockcanbeswitchedtotheLIRC

oscillatorafterwakeup.

• Thereareperipheralfunctions,suchasWDTandTMs,forwhichthefSYSisused.Ifthesystem

clocksourceisswitchedfromfHtofL,theclocksourcetotheperipheralfunctionsmentioned

abovewillchangeaccordingly.

• Theon/offconditionoffSUBandfSdependsuponwhethertheWDTisenabledordisabledasthe

WDTclocksourceisselectedfromfLIRC.

Watchdog Timer

TheWatchdogTimerisprovidedtopreventprogrammalfunctionsorsequencesfromjumpingto

unknownlocations,duetocertainuncontrollableexternaleventssuchaselectricalnoise.

Watchdog Timer Clock Source

TheWatchdogTimerclocksourceisprovidedbytheinternalclock,fLIRC,whichissourcedfromthe

LIRCoscillator.TheWatchdogTimersourceclockisthensubdividedbyaratioof28to218togive

longertimeouts,theactualvaluebeingchosenusingtheWS2~WS0bitsintheWDTCregister.The

LIRCinternaloscillatorhasanapproximateperiodof32kHzatasupplyvoltageof5V.

However,itshouldbenotedthatthisspecifiedinternalclockperiodcanvarywithVDD,temperature

andprocessvariations.TheWDTcanbechosenusingaconfigurationoptiontobealwaysenabled

orenabled/disabledusingtheWDTCregister.

Watchdog Timer Control Register

Asingleregister,WDTC,controlstherequiredtimeoutperiodaswellastheenable/disable

operation.TheWRFsoftwareresetflagwillbeindicatedintheCTRLregister.Thisregistertogether

withaconfigurationoptioncontroltheoveralloperationoftheWatchdogTimer.

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