HT45F2020 datasheet(35/85 Pages) HOLTEK

35 / 85 page

Rev. 1.00

April 11, 2017

Rev. 1.00

April 11, 2017

HT45F2020/HT45F2022

Sound Effect Generator Flash MCU

HT45F2020/HT45F2022

Sound Effect Generator 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.

Reset Functions

Therearethreewaysinwhicharesetcanoccur,eachofwhichwillbedescribedasfollows.

Power-on Reset

Themostfundamentalandunavoidableresetistheonethatoccursafterpowerisfirstappliedto

themicrocontroller.AswellasensuringthattheProgramMemorybeginsexecutionfromthefirst

memoryaddress,apower-onresetalsoensuresthatcertainotherregistersarepresettoknown

conditions.AlltheI/Oportandportcontrolregisterswillpowerupinahighconditionensuringthat

allI/Oportswillbefirstsettoinputs.

VDD

Power-on Reset

SST Time-out

tRSTD

Note:tRSTDispower-ondelaywithtypicaltime=50ms

Power-On Reset Timing Chart

Watchdog Time-out Reset during Normal Operation

TheWatchdogtime-outResetduringnormaloperationisalittledifferentfromPower-onreset.Most

oftheconditionsremainunchangedexceptthattheWatchdogtime-outflagTOwillbesetto“1”.

WDT Time-out

Internal Reset

tRSTD + tSST

Note:tRSTDispower-ondelaywithtypicaltime=16.7ms

WDT Time-out Reset during Normal Operation Timing Chart

HT45F2020 датащи(PDF) 35 Page - Holtek Semiconductor Inc