HT45F2020 datasheet(16/85 Pages) HOLTEK

16 / 85 page

Rev. 1.00

April 11, 2017

Rev. 1.00

April 11, 2017

HT45F2020/HT45F2022

Sound Effect Generator Flash MCU

HT45F2020/HT45F2022

Sound Effect Generator Flash MCU

Theaccompanyingdiagramillustratestheaddressingdataflowofthelook-uptable.

PC High Byte

TBLP Register

Data

14 bits

Program Memory

User Selected

High Byte

Low Byte

Last page or

present page

PC9~PC8

Table Program Example

Thefollowingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfromthe

microcontroller.ThisexampleusesrawtabledatalocatedintheProgramMemorywhichisstored

thereusingtheORGstatement.ThevalueatthisORGstatementis“300H”whichreferstothestart

addressofthelastpagewithinthe1KwordsProgramMemoryofthedevice.Thetablepointeris

setupheretohaveaninitialvalueof“06H”.Thiswillensurethatthefirstdatareadfromthedata

tablewillbeattheProgramMemoryaddress“306H”or6locationsafterthestartofthelastpage.

Notethatthevalueforthetablepointerisreferencedtothefirstaddressofthespecificpageifthe

“TABRDC[m]”instructionisbeingused.Thehighbyteofthetabledatawhichinthiscaseisequal

tozerowillbetransferredtotheTBLHregisterautomaticallywhenthe“TABRDC[m]”instruction

isexecuted.

BecausetheTBLHregisterisaread-onlyregisterandcannotberestored,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 present page

tabrdc tempreg1

; transfers value in table referenced by table pointer,

; data at program memory address “306H” transferred to tempreg1

; and TBLH

dec tblp

; reduce value of table pointer by one

tabrdc tempreg2

; transfers value in table referenced by table pointer,

; data at program memory address “305H” transferred to tempreg2 and

; TBLH in this example the data “1AH” is transferred to tempreg1 and

; data “0FH” to register tempreg2

org 300h

; sets initial address of program memory

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

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