HT45F3W datasheet(22/167 Pages) HOLTEK

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Rev. 1.50

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HT45F3W

R-Type Blood Pressure Meter Flash MCU

HT45F3W

R-Type Blood Pressure Meter Flash MCU

Aftersettingupthetablepointer,thetabledatacanberetrievedfromtheProgramMemoryusing

the“TABRD[m]”or“TABRDL[m]”instructions,respectively.Whentheinstructionisexecuted,

thelowerordertablebytefromtheProgramMemorywillbetransferredtotheuserdefined

DataMemoryregister[m]asspecifiedintheinstruction.Thehigherordertabledatabytefrom

theProgramMemorywillbetransferredtotheTBLHspecialregister.Anyunusedbitsinthis

transferredhigherorderbytewillbereadas0.

Theaccompanyingdiagramillustratestheaddressingdataflowofthelook-uptable.

R egi st er T BL H

Us er S el ec te d

R egi st er

Hi gh By te

Low B yt e

TB LP R egi st er

Da ta

16 bi ts

Pr og ra m Me mo ry

Las t page or

TB HP R eg is te r

Table Program Example

Thefollowingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfrom

themicrocontroller.Thisexampleusesrawtabledatalocatedinthelastpagewhichisstoredthere

usingthe“ORG”and“rombank”statements.ThevalueatthisORGstatementis“1F00H”which

islocatedinROMBank1whichreferstothestartaddressofthelastpagewithinthe16Kwords

ProgramMemory.Thetablepointerlowbyteregisterissetupheretohaveaninitialvalueof“06H”.

ThiswillensurethatthefirstdatareadfromthedatatablewillbeattheProgramMemoryaddress

“3F06H”or6locationsafterthestartofthelastpage.Notethatthevalueforthetablepointeris

referencedtothefirstaddressofthepresentpageifthe“TABRD[m]”instructionisbeingused.The

highbyteofthetabledatawhichinthiscaseisequaltozerowillbetransferredtotheTBLHregister

automaticallywhenthe“TABRD[m]”instructionisexecuted.

BecausetheTBLHregisterisaread-onlyregisterandcannotberestored,careshouldbetaken

toensureitsprotectionifboththemainroutineandInterruptServiceRoutineusetableread

instructions.Ifusingthetablereadinstructions,theInterruptServiceRoutinesmaychangethe

valueoftheTBLHandsubsequentlycauseerrorsifusedagainbythemainroutine.Asaruleitis

recommendedthatsimultaneoususeofthetablereadinstructionsshouldbeavoided.However,in

situationswheresimultaneoususecannotbeavoided,theinterruptsshouldbedisabledpriortothe

executionofanymainroutinetable-readinstructions.Notethatalltablerelatedinstructionsrequire

twoinstructioncyclestocompletetheiroperation.

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