HT82B42RE datasheet(41/84 Pages) HOLTEK

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Rev. 1.10

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HT82B42R/HT82B42RE

I/O MCU with USB Interface

MoreinformationregardingexternalresetcircuitsislocatedinApplicationNoteHA0075Eonthe

Holtekwebsite.

ThistypeofresetoccurswhenthemicrocontrollerisalreadyrunningandtheRESpinis

forcefullypulledlowbyexternalhardwaresuchasanexternalswitch.Inthiscaseasinthecase

ofotherreset,theProgramCounterwillresettozeroandprogramexecutioninitiatedfromthis

point.Notethatastheexternalresetpinisalsopin-sharedwithPE2ifitistobeusedasareset

pin,thecorrectresetconfigurationoptionmustbeselected.

RE S

SST T im e- out

In te r nal R es et

0. 9 V DD

0. 4 V DD

t RS TD

RES

Reset Timing Chart

• LowVoltageReset–LVR

Themicrocontrollercontainsalowvoltageresetcircuitinordertomonitorthesupplyvoltageof

thedevice.TheLVRfunctionisselectedviaaconfigurationoption.Ifthesupplyvoltageofthe

devicedropstowithinarangeof0.9V~VLVRsuchasmightoccurwhenchangingthebattery,the

LVRwillautomaticallyresetthedeviceinternally.ForavalidLVRsignal,alowsupplyvoltage,

i.e.,avoltageintherangebetween0.9V~VLVRmustexistforatimegreaterthanthatspecifiedby

tLVRintheA.C.characteristics.Ifthelowsupplyvoltagestatedoesnotexceedthisvalue,theLVR

willignorethelowsupplyvoltageandwillnotperformaresetfunction.TheactualVLVRvalue

canbeselectedviaconfigurationoptions.

LV R

SST T im e- out

In te r nal R es et

t RS TD

Low Voltage Reset Timing Chart

• WatchdogTime-outResetduringNormalOperation

TheWatchdogtime-outResetduringnormaloperationisthesameasahardwareRESpinreset

exceptthattheWatchdogtime-outflagTOwillbesetto"1".

WD T Ti me -o ut

SST T im e- out

In te r nal R es et

t RS TD

WDT Time-out Reset during Normal Operation Timing Chart

• WatchdogTime-outResetduringPowerDown

TheWatchdogtime-outResetduringPowerDownisalittledifferentfromotherkindsofreset.

MostoftheconditionsremainunchangedexceptthattheProgramCounterandtheStackPointer

willbeclearedto"0"andtheTOflagwillbesetto"1".RefertotheA.C.CharacteristicsfortSST

details.

WD T Ti me -o ut

SST T im e- out

t SST

WDT Time-out Reset during Power Down Timing Char

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