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HT67F5652 датащи(PDF) 66 Page - Holtek Semiconductor Inc |
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HT67F5652 датащи(HTML) 66 Page - Holtek Semiconductor Inc |
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66 / 224 page ![]() Rev. 1.00 �� De�e��e� 0�� �01� Rev. 1.00 �� De�e��e� 0�� �01� HT67F5652 24-Bit Delta Sigma A/D + LCD Flash MCU HT67F5652 24-Bit Delta Sigma A/D + LCD Flash MCU Reset and Initialisation Aresetfunctionisafundamentalpartofanymicrocontrollerensuringthatthedevicecanbeset tosomepredeterminedconditionirrespectiveofoutsideparameters.Themostimportantreset conditionisafterpowerisfirstappliedtothemicrocontroller.Inthiscase,internalcircuitrywill ensurethatthemicrocontroller,afterashortdelay,willbeinawell-definedstateandreadyto executethefirstprograminstruction.Afterthispower-onreset,certainimportantinternalregisters willbesettodefinedstatesbeforetheprogramcommences.OneoftheseregistersistheProgram Counter,whichwillberesettozeroforcingthemicrocontrollertobeginprogramexecutionfromthe lowestProgramMemoryaddress. AnothertypeofresetiswhentheWatchdogTimeroverflowsandresets.Alltypesofresetoperations resultindifferentregisterconditionsbeingsetup.AnotherresetexistsintheformofaLowVoltage Reset,LVR,whereafullreset,isimplementedinsituationswherethepowersupplyvoltagefalls belowacertainthreshold. Reset Functions Therearefourwaysinwhicharesetcanoccur,througheventsoccurringinternally: Power-on Reset Themostfundamentalandunavoidableresetistheonethatoccursafterpowerisfirstappliedto themicrocontroller.AswellasensuringthattheProgramMemorybeginsexecutionfromthefirst memoryaddress,apower-onresetalsoensuresthatcertainotherregistersarepresettoknown conditions.AlltheI/Oportandportcontrolregisterswillpowerupinahighconditionensuringthat allI/Oportswillbefirstsettoinputs. VDD Powe�-on Reset SST Ti�e-out tRSTD Power-On Reset Timing Chart Low Voltage Reset – LVR Themicrocontrollercontainsalowvoltageresetcircuitinordertomonitorthesupplyvoltageofthe device.TheLVRfunctionisalwaysenabledwithaspecificLVRvoltageVLVR.Ifthesupplyvoltageof thedevicedropstowithinarangeof0.9V~VLVRsuchasmightoccurwhenchangingthebattery,the LVRwillautomaticallyresetthedeviceinternallyandtheLVRFbitintheCTRLregisterwillalsobe sethigh.ForavalidLVRsignal,alowsupplyvoltage,i.e.,avoltageintherangebetween0.9V~VLVR mustexistforatimegreaterthanthatspecifiedbytLVRintheA.C.characteristics.Ifthelowsupply voltagestatedoesnotexceedthisvalue,theLVRwillignorethelowsupplyvoltageandwillnot performaresetfunction.TheactualVLVRvaluecanbeselectedbytheLVSbitsintheLVRCregister. IftheLVS7~LVS0bitsarechangedtosomecertainvaluesbytheenvironmentalnoiseorsoftware setting,theLVRwillresetthedeviceafter2~3LIRCclockcycles.Whenthishappens,theLRFbitin theCTRLregisterwillbesethigh.Afterpowerontheregisterwillhavethevalueof01010101B.Note thattheLVRfunctionwillbeautomaticallydisabledwhenthedeviceentersthepowerdownmode. LVR Inte�nal Reset tRSTD + tSST Low Voltage Reset Timing Chart |
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