HT66F4530 datasheet(66/224 Pages) HOLTEK

66 / 224 page

Rev. 1.00

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HT66F4530/HT66F4540/HT66F4550

A/D Flash MCU with Dual Operational Amplifiers

HT66F4530/HT66F4540/HT66F4550

A/D Flash MCU with Dual Operational Amplifiers

Reset and Initialisation

Aresetfunctionisafundamentalpartofanymicrocontrollerensuringthatthesedevicescanbe

settosomepredeterminedconditionirrespectiveofoutsideparameters.Themostimportantreset

conditionisafterpowerisfirstappliedtothemicrocontroller.Inthiscase,internalcircuitrywill

ensurethatthemicrocontroller,afterashortdelay,willbeinawell-definedstateandreadyto

executethefirstprograminstruction.Afterthispower-onreset,certainimportantinternalregisters

willbesettodefinedstatesbeforetheprogramcommences.OneoftheseregistersistheProgram

Counter,whichwillberesettozeroforcingthemicrocontrollertobeginprogramexecutionfromthe

lowestProgramMemoryaddress.

Inadditiontothepower-onreset,situationsmayarisewhereitisnecessarytoforcefullyapplya

resetconditionwhenthesedevicesarerunning.Oneexampleofthisiswhereafterpowerhasbeen

appliedandthesedevicesarealreadyrunning,theRESlineisforcefullypulledlow.Insuchacase,

knownasanormaloperationreset,someoftheregistersremainunchangedallowingthesedevices

toproceedwithnormaloperationaftertheresetlineisallowedtoreturnhigh.

AnothertypeofresetiswhentheWatchdogTimeroverflowsandresetsthemicrocontroller.All

typesofresetoperationsresultindifferentregisterconditionsbeingsetup.Anotherresetexistsin

theformofaLowVoltageReset,LVR,whereafullreset,similartotheRESresetisimplementedin

situationswherethepowersupplyvoltagefallsbelowacertainthreshold.

Reset Functions

Thereareseveralwaysinwhichamicrocontrollerresetcanoccur,througheventsoccurringboth

internallyandexternally:

Power-on Reset

Themostfundamentalandunavoidableresetistheonethatoccursafterpowerisfirstappliedto

themicrocontroller.AswellasensuringthattheProgramMemorybeginsexecutionfromthefirst

memoryaddress,apower-onresetalsoensuresthatcertainotherregistersarepresettoknown

conditions.AlltheI/Oportandportcontrolregisterswillpowerupinahighconditionensuringthat

allpinswillbefirstsettoinputs.

Inte�nal Reset

tRSTD+tSST

0.9VDD

RES

VDD

Power-on Reset Timing Chart

HT66F4530 数据表(PDF) 66 Page - Holtek Semiconductor Inc

HT66F4530 数据表(HTML) 66 Page - Holtek Semiconductor Inc

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