HT68F005 datasheet(44/93 Pages) HOLTEK

44 / 93 page

Rev. 1.00

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Rev. 1.00

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HT68F005/HT68F006

Enhanced I/O Flash Type MCU

HT68F005/HT68F006

Enhanced I/O Flash Type MCU

Reset Functions

Thereareseveralwaysinwhichamicrocontrollerresetcanoccur,througheventsoccurringboth

internallyandexternally:

• Power-onReset

Themostfundamentalandunavoidableresetistheonethatoccursafterpowerisfirstappliedto

themicrocontroller.AswellasensuringthattheProgramMemorybeginsexecutionfromthefirst

memoryaddress,apower-onresetalsoensuresthatcertainotherregistersarepresettoknown

conditions.AlltheI/Oportandportcontrolregisterswillpowerupinahighconditionensuring

thatallpinswillbefirstsettoinputs.

RE S

VD D

In te r nal R es et

0. 9 V DD

t RS TD + t SST

Note:tRSTDispower-ondelay,typicaltime=50ms

Power-on Reset Timing Chart

• LowVoltageReset–LVR

Themicrocontrollerscontainalowvoltageresetcircuitinordertomonitorthesupplyvoltageof

thedevicesandprovideanMCUresetshouldthevaluefallbelowacertainpredefinedlevel.

TheLVRfunctionisalwaysenabledwithaspecificLVRvoltageVLVR.Ifthesupplyvoltageof

thedevicesdroptowithinarangeof0.9V~VLVRsuchasmightoccurwhenchangingthebattery

inbatterypoweredapplications,theLVRwillautomaticallyresetthedevicesinternallyandthe

LVRFbitintheCTRLregisterwillalsobesetto1.ForavalidLVRsignal,alowsupplyvoltage,

i.e.,avoltageintherangebetween0.9V~VLVRmustexistforatimegreaterthanthatspecified

bytLVRintheA.C.characteristics.Ifthelowsupplyvoltagestatedoesnotexceedthisvalue,

theLVRwillignorethelowsupplyvoltageandwillnotperformaresetfunction.Theactual

VLVRvaluecanbeselectedbytheLVSbitsintheLVRCregister.IftheLVS7~LVS0bitsare

changedtosomedifferentvaluesbyenvironmentalnoise,theLVRwillresetthedevicesafter

2~3LIRCclockcycles.Whenthishappens,theLRFbitintheCTRLregisterwillbesetto1.

Afterpowerontheregisterwillhavethevalueof01010101B.NotethattheLVRfunctionwillbe

automaticallydisabledwhenthedevicesenterthepowerdownmode.

LV R

In te r nal R es et

t RS TD + t SST

Note:tRSTDispower-ondelay,typicaltime=16.7ms

Low Voltage Reset Timing Chart

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