Moteur de recherche de fiches techniques de composants électroniques |
|
HT45R4U Fiches technique(PDF) 67 Page - Holtek Semiconductor Inc |
|
HT45R4U Fiches technique(HTML) 67 Page - Holtek Semiconductor Inc |
67 / 105 page Rev. 1.10 66 �a��� 1�� �01� Rev. 1.10 67 �a��� 1�� �01� HT45R4U TinyPowerTM A/D Type e-Banking ASSP OTP MCU with LCD Reset and Initialisation Aresetfunctionisafundamentalpartofanymicrocontrollerensuringthatthedevicecanbeset tosomepredeterminedconditionirrespectiveofoutsideparameters.Themostimportantreset conditionisafterpowerisfirstappliedtothemicrocontroller.Inthiscase,internalcircuitrywill ensurethatthemicrocontroller,afterashortdelay,willbeinawelldefinedstateandreadyto executethefirstprograminstruction.Afterthispower-onreset,certainimportantinternalregisters willbesettodefinedstatesbeforetheprogramcommences.OneoftheseregistersistheProgram Counter,whichwillberesettozeroforcingthemicrocontrollertobeginprogramexecutionfromthe lowestProgramMemoryaddress. Inadditiontothepower-onreset,situationsmayarisewhereitisnecessarytoforcefullyapplya resetconditionwhenthemicrocontrollerisrunning.Oneexampleofthisiswhereafterpowerhas beenappliedandthemicrocontrollerisalreadyrunning,theRESlineisforcefullypulledlow.In suchacase,knownasanormaloperationreset,someoftheregistersremainunchangedallowing themicrocontrollertoproceedwithnormaloperationaftertheresetlineisallowedtoreturnhigh. AnothertypeofresetiswhentheWatchdogTimeroverflowsandresetsthemicrocontroller.All typesofresetoperationsresultindifferentregisterconditionsbeingsetup. AnotherresetexistsintheformofaLowVoltageReset,LVR,whereafullreset,similartotheRES resetisimplementedinsituationswherethepowersupplyvoltagefallsbelowacertainthreshold. Reset Functions Therearefivewaysinwhichamicrocontrollerresetcanoccur,througheventsoccurringbothinternally andexternally: Power-on Reset Themostfundamentalandunavoidableresetistheonethatoccursafterpowerisfirstappliedtothe microcontroller.AswellasensuringthattheProgramMemorybeginsexecutionfromthefirstmemory address,apower-onresetalsoensuresthatcertainotherregistersarepresettoknownconditions.Allthe I/Oportandportcontrolregisterswillpowerupinahighconditionensuringthatallpinswillbefirstset toinputs. AlthoughthemicrocontrollerhasaninternalRCresetfunction,iftheVDDpowersupplyrisetime isnotfastenoughordoesnotstabilisequicklyatpower-on,theinternalresetfunctionmaybe incapableofprovidingproperresetoperation.Forthisreasonitisrecommendedthatanexternal RCnetworkisconnectedtotheRESpin,whoseadditionaltimedelaywillensurethattheRESpin remainslowforanextendedperiodtoallowthepowersupplytostabilise.Duringthistimedelay, normaloperationofthemicrocontrollerwillbeinhibited.AftertheRESlinereachesacertain voltagevalue,theresetdelaytimetRSTDisinvokedtoprovideanextradelaytimeafterwhichthe microcontrollerwillbeginnormaloperation.TheabbreviationSSTinthefiguresstandsforSystem Start-upTimer. RE S VD D SS T Ti me - out Ch ip R es et 0. 9 V DD t RS TD Power-On Reset Timing Chart FormostapplicationsaresistorconnectedbetweenVDDandtheRESpinandacapacitorconnected betweenVSSandtheRESpinwillprovideasuitableexternalresetcircuit.Anywiringconnectedto theRESpinshouldbekeptasshortaspossibletominimiseanystraynoiseinterference. |
Numéro de pièce similaire - HT45R4U |
|
Description similaire - HT45R4U |
|
|
Lien URL |
Politique de confidentialité |
ALLDATASHEET.FR |
ALLDATASHEET vous a-t-il été utile ? [ DONATE ] |
À propos de Alldatasheet | Publicité | Contactez-nous | Politique de confidentialité | Echange de liens | Fabricants All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |