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HT45F2002

2-Wire Communication Flash MCU

HT45F2002

2-Wire Communication Flash MCU

Logical and Rotate Operation

ThestandardlogicaloperationssuchasAND,OR,XORandCPLallhavetheirowninstruction

withintheHoltekmicrocontrollerinstructionset.Aswiththecaseofmostinstructionsinvolving

datamanipulation,datamustpassthroughtheAccumulatorwhichmayinvolveadditional

programmingsteps.Inalllogicaldataoperations,thezeroflagmaybesetiftheresultofthe

operationiszero.Anotherformoflogicaldatamanipulationcomesfromtherotateinstructionssuch

asRR,RL,RRCandRLCwhichprovideasimplemeansofrotatingonebitrightorleft.Different

rotateinstructionsexistdependingonprogramrequirements.Rotateinstructionsareusefulforserial

portprogrammingapplicationswheredatacanberotatedfromaninternalregisterintotheCarry

bitfromwhereitcanbeexaminedandthenecessaryserialbitsethighorlow.Anotherapplication

whichrotatedataoperationsareusedistoimplementmultiplicationanddivisioncalculations.

Branches and Control Transfer

ProgrambranchingtakestheformofeitherjumpstospecifiedlocationsusingtheJMPinstruction

ortoasubroutineusingtheCALLinstruction.Theydifferinthesensethatinthecaseofa

subroutinecall,theprogrammustreturntotheinstructionimmediatelywhenthesubroutinehas

beencarriedout.Thisisdonebyplacingareturninstruction“RET”inthesubroutinewhichwill

causetheprogramtojumpbacktotheaddressrightaftertheCALLinstruction.InthecaseofaJMP

instruction,theprogramsimplyjumpstothedesiredlocation.Thereisnorequirementtojumpback

totheoriginaljumpingoffpointasinthecaseoftheCALLinstruction.Onespecialandextremely

usefulsetofbranchinstructionsaretheconditionalbranches.Hereadecisionisfirstmaderegarding

theconditionofacertaindatamemoryorindividualbits.Dependingupontheconditions,the

programwillcontinuewiththenextinstructionorskipoveritandjumptothefollowinginstruction.

Theseinstructionsarethekeytodecisionmakingandbranchingwithintheprogramperhaps

determinedbytheconditionofcertaininputswitchesorbytheconditionofinternaldatabits.

Bit Operations

TheabilitytoprovidesinglebitoperationsonDataMemoryisanextremelyflexiblefeatureofall

Holtekmicrocontrollers.Thisfeatureisespeciallyusefulforoutputportbitprogrammingwhere

individualbitsorportpinscanbedirectlysethighorlowusingeitherthe“SET[m].i”or“CLR[m].i”

instructionsrespectively.Thefeatureremovestheneedforprogrammerstofirstreadthe8-bitoutput

port,manipulatetheinputdatatoensurethatotherbitsarenotchangedandthenoutputtheportwith

thecorrectnewdata.Thisread-modify-writeprocessistakencareofautomaticallywhenthesebit

operationinstructionsareused.

Table Read Operations

Datastorageisnormallyimplementedbyusingregisters.However,whenworkingwithlarge

amountsoffixeddata,thevolumeinvolvedoftenmakesitinconvenienttostorethefixeddatain

theDataMemory.Toovercomethisproblem,HoltekmicrocontrollersallowanareaofProgram

Memorytobesetupasatablewheredatacanbedirectlystored.Asetofeasytouseinstructions

providesthemeansbywhichthisfixeddatacanbereferencedandretrievedfromtheProgram

Memory.

Other Operations

Inadditiontotheabovefunctionalinstructions,arangeofotherinstructionsalsoexistsuchas

the“HALT”instructionforPower-downoperationsandinstructionstocontroltheoperationof

theWatchdogTimerforreliableprogramoperationsunderextremeelectricorelectromagnetic

environments.Fortheirrelevantoperations,refertothefunctionalrelatedsections.