HT82B42R datasheet(19/86 Pages) HOLTEK

19 / 86 page

Rev. 1.00

October 27, 2011

Rev. 1.00

October 27, 2011

HT82B42R/HT82B42RE

I/O MCU with USB Interface

Table Program Example

Thefollowingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfrom

themicrocontroller.Thisexampleusesrawtabledatalocatedinthelastpagewhichisstoredthere

usingtheORGstatement.ThevalueatthisORGstatementis"F00H"whichreferstothestart

addressofthelastpagewithinthe4KProgramMemoryofdevice.Thetablepointerissetuphere

tohaveaninitialvalueof"06H".Thiswillensurethatthefirstdatareadfromthedatatablewillbe

attheProgramMemoryaddress"F06H"or6locationsafterthestartofthelastpage.Notethatthe

valueforthetablepointerisreferencedtothefirstaddressofthepresentpageifthe"TABRDC[m]"

instructionisbeingused.Thehighbyteofthetabledatawhichinthiscaseisequaltozerowillbe

transferredtotheTBLHregisterautomaticallywhenthe"TABRDL[m]"instructionisexecuted.

tempreg1

; temporary register #1

tempreg2

; temporary register #2

mov a,06h

; initialise table pointer-note that this

; address is referenced

mov tblp,a

; to the last page or present page

tabrdl

tempreg1

; transfers value in table referenced by table

; pointer to tempregl data at prog. memory

; address "F06H" transferred to tempreg1 and TBLH

dec tblp

; reduce value of table pointer by one

tabrdl

tempreg2

; transfers value in table referenced by table

; pointer to tempreg2 data at prog. memory

; address "F05H" transferred to tempreg2 and TBLH

; in this example the data "1AH" is transferred

; to tempreg1 and data "0FH" to register tempreg2

; the value "00H" will be transferred to the high

; byte register TBLH

org F00h

; sets initial address of last page

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

BecausetheTBLHregisterisaread-onlyregisterandcannotberestored,careshouldbetaken

toensureitsprotectionifboththemainroutineandInterruptServiceRoutineusethetableread

instructions.Ifusingthetablereadinstructions,theInterruptServiceRoutinesmaychangethe

valueofTBLHandsubsequentlycauseerrorsifusedagainbythemainroutine.Asaruleitis

recommendedthatsimultaneoususeofthetablereadinstructionsshouldbeavoided.However,in

situationswheresimultaneoususecannotbeavoided,theinterruptsshouldbedisabledpriortothe

executionofanymainroutinetable-readinstructions.Notethatalltablerelatedinstructionsrequire

twoinstructioncyclestocompletetheiroperation.

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