HT45F5Q datasheet(45/114 Pages) HOLTEK

45 / 114 page

Rev. 1.10

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Rev. 1.10

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HT45F5Q

Charger Flash MCU

HT45F5Q

Charger Flash MCU

Bit6~4

Unimplemented,readas“0”

Bit3

RSTF:ResetcausedbyRSTCsetting

0:Notactive

1:Active

Thisbitcanbeclearto“0”,butcannotsetto“1”.Ifthisbitisset,onlyclearedby

SoftwareorPORreset.

Bit2

LVRF:LVRfunctionresetflag

0:Notactive

1:Active

Thisbitcanbeclearto“0”,butcannotbesetto“1”.

Bit1

Unimplemented,readas“0”

Bit0

WRF:WDTControlregistersoftwareresetflag

0:Notoccur

1:Occurred

Thisbitissetto1bytheWDTControlregistersoftwareresetandclearedbythe

applicationprogram.Notethatthisbitcanonlybeclearedto0bytheapplication

program.

Watchdog Timer Operation

TheWatchdogTimeroperatesbyprovidingadeviceresetwhenitstimeroverflows.Thismeans

thatintheapplicationprogramandduringnormaloperationtheuserhastostrategicallyclearthe

WatchdogTimerbeforeitoverflowstopreventtheWatchdogTimerfromexecutingareset.Thisis

doneusingtheclearwatchdoginstructions.Iftheprogrammalfunctionsforwhateverreason,jumps

toanunknownlocation,orentersanendlessloop,theclearWDTinstructionswillnotbeexecuted

inthecorrectmanner,inwhichcasetheWatchdogTimerwilloverflowandresetthedevice.With

regardtotheWatchdogTimerenable/disablefunction,therearefivebits,WE4~WE0,intheWDTC

registertoadditionalenable/disableandresetcontroloftheWatchdogTimer.

WE4 ~ WE0 Bits

WDT Function

10101B

Disa�le

01010B

Ena�le

Any othe� value

Reset MCU

Watchdog Timer Enable/Disable Control

Undernormalprogramoperation,aWatchdogTimertime-outwillinitialiseadeviceresetandset

thestatusbitTO.However,ifthesystemisintheSLEEPorIDLEMode,whenaWatchdogTimer

time-outoccurs,theTObitinthestatusregisterwillbesetandonlytheProgramCounterandStack

Pointerwillbereset.FourmethodscanbeadoptedtoclearthecontentsoftheWatchdogTimer.

ThefirstisaWDTreset,whichmeansavalueotherthan01010Band10101Biswrittenintothe

WE4~WE0bitlocations,thesecondisanexternalhardwarereset,whichmeansalowlevelonthe

externalresetpin,thethirdisusingtheWatchdogTimersoftwareclearinstructionandthefourth

isviaaHALTinstruction.Thereisonlyonemethodofusingsoftwareinstructiontoclearthe

WatchdogTimer.Thatistousethesingle“CLRWDT”instructiontocleartheWDT.

Themaximumtime-outperiodiswhenthe215divisionratioisselected.Asanexample,witha32kHz

LIRCoscillatorasitssourceclock,thiswillgiveamaximumwatchdogperiodofaround1second

forthe215divisionratio,andaminimumtimeoutof8msforthe28divisionration.

HT45F5Q Datasheet(PDF) 45 Page - Holtek Semiconductor Inc

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