HT67F488 datasheet(22/171 Pages) HOLTEK

22 / 171 page

Rev. 1.60

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

Look-up Table

AnylocationwithintheProgramMemorycanbedefinedasalook-uptablewhereprogrammerscan

storefixeddata.Tousethelook-uptable,thetablepointermustfirstbesetupbyplacingtheaddress

ofthelookupdatatoberetrievedinthetablepointerregister,TBLPandTBHP.Theseregisters

definethetotaladdressofthelook-uptable.

Aftersettingupthetablepointer,thetabledatacanberetrievedfromtheProgramMemoryusing

the“TABRD[m]”or“TABRDL[m]”instructionsrespectivelywhenthememory[m]islocatedin

currentpage.Ifthememory[m]islocatedinotherpages,thetabledatacanberetrievedfromthe

ProgramMemoryusingthe“LTABRD[m]”or“LTABRDL[m]”instructionsrespectively.Whenthe

instructionisexecuted,thelowerordertablebytefromtheProgramMemorywillbetransferredto

theuserdefinedDataMemoryregister[m]asspecifiedintheinstruction.Thehigherordertabledata

bytefromtheProgramMemorywillbetransferredtotheTBLHspecialregister.Anyunusedbitsin

thistransferredhigherorderbytewillbereadas0.

Theaccompanyingdiagramillustratestheaddressingdataflowofthelook-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

TB LP R eg is te r

Da ta

16 b it s

Pr og ra m Me mo ry

Las t p age o r

TB HP R egi st er

Table Program Example

Thefollowingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfromthe

microcontroller.ThisexampleusesrawtabledatalocatedintheProgramMemorywhichisstored

thereusingtheORGstatement.ThevalueatthisORGstatementis“F00H”whichreferstothestart

addressofthelastpagewithinthe4KProgramMemoryoftheHT67F488device.Thetablepointer

issetupheretohaveaninitialvalueof“06H”.Thiswillensurethatthefirstdatareadfromthedata

tablewillbeattheProgramMemoryaddress“F06H”or6locationsafterthestartofthelastpage.

Notethatthevalueforthetablepointerisreferencedtothefirstaddressofthepresentpageifthe

“TABRD[m]”or“LTABRD[m]”instructionisbeingused.Thehighbyteofthetabledatawhichin

thiscaseisequaltozerowillbetransferredtotheTBLHregisterautomaticallywhenthe“TABRD

[m]”or“LTABRD[m]”instructionisexecuted.

BecausetheTBLHregisterisaread/writeregisterandcanberestored,careshouldbetaken

toensureitsprotectionifboththemainroutineandInterruptServiceRoutineusetableread

instructions.Ifusingthetablereadinstructions,theInterruptServiceRoutinesmaychangethe

valueoftheTBLHandsubsequentlycauseerrorsifusedagainbythemainroutine.Asaruleitis

recommendedthatsimultaneoususeofthetablereadinstructionsshouldbeavoided.However,in

situationswheresimultaneoususecannotbeavoided,theinterruptsshouldbedisabledpriortothe

executionofanymainroutinetable-readinstructions.Notethatalltablerelatedinstructionsrequire

twoinstructioncyclestocompletetheiroperation.

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