HT45F39 datasheet(14/102 Pages) HOLTEK

14 / 102 page

Rev. 1.10

July 01, 2016

Rev. 1.10

July 01, 2016

HT45F39/HT45F391

Ultrasonic Distance Measurement 8-bit Flash MCU

HT45F39/HT45F391

Ultrasonic Distance Measurement 8-bit Flash MCU

System Architecture

Akeyfactorinthehigh-performancefeaturesoftheHoltekrangeofmicrocontrollersisattributed

totheinternalsystemarchitecture.Therangeofdevicestakeadvantageoftheusualfeaturesfound

withinRISCmicrocontrollersprovidingincreasedspeedofoperationandenhancedperformance.

Thepipeliningschemeisimplementedinsuchawaythatinstructionfetchingandinstruction

executionareoverlapped,henceinstructionsareeffectivelyexecutedinonecycle,withthe

exceptionofbranchorcallinstructions.An8-bitwideALUisusedinpracticallyalloperations

oftheinstructionset.Itcarriesoutarithmeticoperations,logicoperations,rotation,increment,

decrement,branchdecisions,etc.Theinternaldatapathissimplifiedbymovingdatathroughthe

AccumulatorandtheALU.CertaininternalregistersareimplementedintheDataMemoryand

canbedirectlyorindirectlyaddressed.Thesimpleaddressingmethodsoftheseregistersalong

withadditionalarchitecturalfeaturesensurethataminimumofexternalcomponentsisrequired

toprovideafunctionalI/OandA/Dcontrolsystemwithmaximumreliabilityandflexibility.This

makesthedevicessuitableforlow-cost,high-volumeproductionforcontrollerapplications.

Clocking and Pipelining

Themainsystemclock,derivedfromRCoscillatorissubdividedintofourinternallygenerated

non-overlappingclocks,T1~T4.TheProgramCounterisincrementedatthebeginningoftheT1

clockduringwhichtimeanewinstructionisfetched.TheremainingT2~T4clockscarryoutthe

decodingandexecutionfunctions.Inthisway,oneT1~T4clockcycleformsoneinstructioncycle.

Althoughthefetchingandexecutionofinstructionstakesplaceinconsecutiveinstructioncycles,the

pipeliningstructureofthemicrocontrollerensuresthatinstructionsareeffectivelyexecutedinone

instructioncycle.TheexceptiontothisareinstructionswherethecontentsoftheProgramCounter

arechanged,suchassubroutinecallsorjumps,inwhichcasetheinstructionwilltakeonemore

instructioncycletoexecute.

Forinstructionsinvolvingbranches,suchasjumporcallinstructions,twoinstructioncyclesare

requiredtocompleteinstructionexecution.Anextracycleisrequiredastheprogramtakesone

cycletofirstobtaintheactualjumporcalladdressandthenanothercycletoactuallyexecutethe

branch.Therequirementforthisextracycleshouldbetakenintoaccountbyprogrammersintiming

sensitiveapplications.

Fe tc h In st . ( PC )

Ex ec ut e In st . (P C- 1)

Fe tc h In st . ( PC +1 )

Ex ec ut e In st . (P C)

Fe tc h In s t. (P C+ 2)

Ex ec ut e In st . (P C+ 1)

PC +1

PC +2

O sci ll at or C lo ck

(S yst em C lo ck)

P has e Cl o ck T 1

Pr og ra m C oun te r

P has e Cl o ck T 2

P has e Cl o ck T 3

P has e Cl o ck T 4

Pi pel in in g

System Clocking and Pipelining

HT45F39 Datasheet(PDF) 14 Page - Holtek Semiconductor Inc

HT45F39 Datasheet(HTML) 14 Page - Holtek Semiconductor Inc

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