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HT45F39 Datasheet(PDF) 18 Page - Holtek Semiconductor Inc |
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HT45F39 Datasheet(HTML) 18 Page - Holtek Semiconductor Inc |
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18 / 102 page  Rev. 1.10 18 July 01, 2016 Rev. 1.10 19 July 01, 2016 HT45F39/HT45F391 Ultrasonic Distance Measurement 8-bit Flash MCU HT45F39/HT45F391 Ultrasonic Distance Measurement 8-bit Flash MCU Look-up Table AnylocationwithintheProgramMemorycanbedefinedasalook-uptablewhereprogrammers canstorefixeddata.Tousethelook-uptable,thetablepointermustfirstbesetupbyplacingthe lowerorderaddressofthelookupdatatoberetrievedinthetablepointerregister,TBLP.This registerdefinesthelower8-bitaddressofthelook-uptable.Aftersettingupthetablepointer, thetabledatacanberetrievedfromthecurrentProgramMemorypageorlastProgramMemory pageusingtheTABRDC[m]orTABRDL[m]instructions,respectively.Whentheseinstructions areexecuted,thelowerordertablebytefromtheProgramMemorywillbetransferredtotheuser definedDataMemoryregister[m]asspecifiedintheinstruction.Thehigherordertabledatabyte fromtheProgramMemorywillbetransferredtotheTBLHspecialregister.Anyunusedbitsinthis transferredhigherorderbytewillbereadas0. Thefollowingdiagramillustratestheaddressing/dataflowofthelook-uptable: Re gi st er T BL H Us er S el ec te d Re gi st er Hi gh B yt eL ow B yt e PC H ig h By te TB LP R eg is te r Da ta 16 b it s Pr og ra m Me mo ry Instruction Table Location Bits b10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 TABRDC [m] PC10 PC9 PC8 @7 @6 @5 @4 @3 @2 @1 @0 TABRDL [m] 1 1 1 @7 @6 @5 @4 @3 @2 @1 @0 Note:PC10~PC8:CurrentProgramCounterbits @7~@0:TablePointerTBLPbits Table Program Example Theaccompanyingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfrom thedevices.Thisexampleusesrawtabledatalocatedinthelastpagewhichisstoredthereusing theORGstatement.ThevalueatthisORGstatementis"0700H"whichreferstothestartaddress ofthelastpagewithinthe2KProgramMemoryofthedevices.Thetablepointerissetuphereto haveaninitialvalueof"06H".Thiswillensurethatthefirstdatareadfromthedatatablewillbeat theProgramMemoryaddress"0706H"or6locationsafterthestartofthelastpage.Notethatthe valueforthetablepointerisreferencedtothefirstaddressofthepresentpageifthe"TABRDC[m]" instructionisbeingused.Thehighbyteofthetabledatawhichinthiscaseisequaltozerowillbe transferredtotheTBLHregisterautomaticallywhenthe"TABRDL[m]"instructionisexecuted. BecausetheTBLHregisterisaread-onlyregisterandcannotberestored,careshouldbetaken toensureitsprotectionifboththemainroutineandInterruptServiceRoutineusethetableread instructions.Ifusingthetablereadinstructions,theInterruptServiceRoutinesmaychangethe valueofTBLHandsubsequentlycauseerrorsifusedagainbythemainroutine.Asaruleitis recommendedthatsimultaneoususeofthetablereadinstructionsshouldbeavoided.However,in situationswheresimultaneoususecannotbeavoided,theinterruptsshouldbedisabledpriortothe executionofanymainroutinetable-readinstructions.Notethatalltablerelatedinstructionsrequire twoinstructioncyclestocompletetheiroperation. |
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