HT45F75 datasheet(22/190 Pages) HOLTEK

22 / 190 page

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HT45F75

Body Fat Scale Flash MCU

HT45F75

Body Fat Scale Flash MCU

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

La st p age o r

TB HP R egi st er

TB LP R eg is te r

Da ta

16bi ts

Pr og ra m Me mo ry

Table Program Example

Thefollowingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfrom

themicrocontroller.ThisexampleusesrawtabledatalocatedintheProgramMemorywhichis

storedthereusingtheORGstatement.ThevalueatthisORGstatementis“0F00H”whichrefersto

thestartaddressofthelastpagewithinthe4KProgramMemoryofthemicrocontroller.Thetable

pointerlowbyteregisterissetupheretohaveaninitialvalueof“06H”.Thiswillensurethatthefirst

datareadfromthedatatablewillbeattheProgramMemoryaddress“0F06H”or6locationsafter

thestartofthelastpage.Notethatthevalueforthetablepointerisreferencedtothefirstaddress

specifiedbyTBLPandTBHPifthe“TABRD[m]”or“LTABRD[m]”instructionisbeingused.The

highbyteofthetabledatawhichinthiscaseisequaltozerowillbetransferredtotheTBLHregister

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

BecausetheTBLHregisterisaread/writeregisterandcanberestored,careshouldbetaken

toensureitsprotectionifboththemainroutineandInterruptServiceRoutineusetableread

instructions.Ifusingthetablereadinstructions,theInterruptServiceRoutinesmaychangethe

valueoftheTBLHandsubsequentlycauseerrorsifusedagainbythemainroutine.Asaruleitis

recommendedthatsimultaneoususeofthetablereadinstructionsshouldbeavoided.However,in

situationswheresimultaneoususecannotbeavoided,theinterruptsshouldbedisabledpriortothe

executionofanymainroutinetable-readinstructions.Notethatalltablerelatedinstructionsrequire

twoinstructioncyclestocompletetheiroperation.

Table Read Program Example

tempreg1 db ?

; temporary register #1

tempreg2 db ?

; temporary register #2

mov a,06h

; initialise low table pointer - note that this address is referenced

mov tblp,a

; to the last page or the page that tbhp pointed

mov a,0Fh

; initialise high table pointer

mov tbhp,a

tabrd tempreg1

; transfers value in table referenced by table pointer data at program

; memory address “0F06H” transferred to tempreg1 and TBLH

dec tblp

; reduce value of table pointer by one

tabrd tempreg2

; transfers value in table referenced by table pointer

; data at program memory address “0F05H” transferred to

; tempreg2 and TBLH in this example the data “1AH” is

; transferred to tempreg1 and data “0FH” to register tempreg2

org 0F00h

; sets initial address of program memory

dc 00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh

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