HT45F56 datasheet(40/90 Pages) HOLTEK

40 / 90 page

Rev. 1.11

April 11, 2017

Rev. 1.11

April 11, 2017

HT45F56

Shock Detector Flash MCU

HT45F56

Shock Detector Flash MCU

Themaximumtimeoutperiodiswhenthe215divisionratioisselected.Asanexample,witha32

kHzLIRCoscillatorasitssourceclock,thiswillgiveamaximumwatchdogperiodofaround1

secondforthe215divisionratioandaminimumtimeoutof7.8msforthe28divisionration.

“

CLR WDT”Instruction

8-stage Divider

WDT Prescaler

WE4~WE0 bits

WDTC

Reset MCU

fSUB

fSUB/28

8-to-1 MUX

CLR

WS2~WS0

(fSUB/28 ~ fSUB/215)

WDT Time-out

(28/fSUB ~ 215/fSUB)

“

HALT”Instruction

RES pin reset

Watchdog Timer

Reset and Initialisation

Aresetfunctionisafundamentalpartofanymicrocontrollerensuringthatthedevicescanbeset

tosomepredeterminedconditionirrespectiveofoutsideparameters.Themostimportantreset

conditionisafterpowerisfirstappliedtothemicrocontroller.Inthiscase,internalcircuitrywill

ensurethatthemicrocontroller,afterashortdelay,willbeinawelldefinedstateandreadyto

executethefirstprograminstruction.Afterthispower-onreset,certainimportantinternalregisters

willbesettodefinedstatesbeforetheprogramcommences.OneoftheseregistersistheProgram

Counter,whichwillberesettozeroforcingthemicrocontrollertobeginprogramexecutionfromthe

lowestProgramMemoryaddress.

Inadditiontothepower-onreset,situationsmayarisewhereitisnecessarytoforcefullyapply

aresetconditionwhenthemicrocontrollerisrunning.Oneexampleofthisiswhereafterpower

hasbeenappliedandthemicrocontrollerisalreadyrunning,theRESlineisforcefullypulledlow.

Insuchacase,knownasanormaloperationreset,someofthemicrocontrollerregistersremain

unchangedallowingthemicrocontrollertoproceedwithnormaloperationaftertheresetlineis

allowedtoreturnhigh.

AnothertypeofresetiswhentheWatchdogTimeroverflowsandresetsthemicrocontroller.All

typesofresetoperationsresultindifferentregisterconditionsbeingsetup.Anotherresetexistsinthe

formofaLowVoltageReset,LVR,whereafullresetisimplementedinsituationswherethepower

supplyvoltagefallsbelowacertainthreshold.

Reset Functions

Therearefivewaysinwhichamicrocontrollerresetcanoccur,througheventsoccurringboth

internallyandexternally.

HT45F56 Datasheet(PDF) 40 Page - Holtek Semiconductor Inc

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