HT45F65 datasheet(28/231 Pages) HOLTEK

28 / 231 page

Rev. 1.60

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HT45F65/HT45F66/HT45F67

Glucose Meter 8-Bit Flash MCU

Look-up Table

AnylocationwithintheProgramMemorycanbedefinedasalook-uptablewhereprogrammerscan

storefixeddata.Tousethelook-uptable,thetablepointermustfirstbesetupbyplacingtheaddress

ofthelookupdatatoberetrievedinthetablepointerregister,TBLPandTBHP.Theseregisters

definethetotaladdressofthelook-uptable.

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

Thefollowingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfromthe

microcontroller.ThisexampleusesrawtabledatalocatedintheProgramMemorywhichisstored

thereusingtheORGstatement.ThevalueatthisORGstatementis"7F00H"whichreferstothestart

addressofthelastpagewithinthe32KProgramMemoryoftheHT45F67.Thetablepointerissetup

heretohaveaninitialvalueof"06H".Thiswillensurethatthefirstdatareadfromthedatatablewill

beattheProgramMemoryaddress"7F06H"or6locationsafterthestartofthelastpage.Notethat

thevalueforthetablepointerisreferencedtothefirstaddressofthepresentpageifthe"TABRD[m]"

instructionisbeingused.Thehighbyteofthetabledatawhichinthiscaseisequaltozerowillbe

transferredtotheTBLHregisterautomaticallywhenthe"TABRD[m]"instructionisexecuted.

BecausetheTBLHregisterisaread-onlyregisterandcannotberestored,careshouldbetaken

toensureitsprotectionifboththemainroutineandInterruptServiceRoutineusetableread

instructions.Ifusingthetablereadinstructions,theInterruptServiceRoutinesmaychangethe

valueoftheTBLHandsubsequentlycauseerrorsifusedagainbythemainroutine.Asaruleitis

recommendedthatsimultaneoususeofthetablereadinstructionsshouldbeavoided.However,in

situationswheresimultaneoususecannotbeavoided,theinterruptsshouldbedisabledpriortothe

executionofanymainroutinetable-readinstructions.Notethatalltablerelatedinstructionsrequire

twoinstructioncyclestocompletetheiroperation.

HT45F65 Datasheet(PDF) 28 Page - Holtek Semiconductor Inc

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