HT69F240 datasheet(19/172 Pages) HOLTEK

19 / 172 page

Rev. 1.20

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Rev. 1.20

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HT69F240

I/O 8-Bit Flash MCU with LED/LCD Driver

HT69F240

I/O 8-Bit Flash MCU with LED/LCD Driver

Special Vectors

WithintheProgramMemory,certainlocationsarereservedfortheresetandinterrupts.Thelocation

000Hisreservedforusebythedeviceresetforprograminitialisation.Afteradeviceresetis

initiated,theprogramwilljumptothislocationandbeginexecution.

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.

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

Theaccompanyingexampleshowshowthetablepointerandtabledataisdefinedandretrievedfrom

thedevice.Thisexampleusesrawtabledatalocatedinthelastpagewhichisstoredthereusing

theORGstatement.ThevalueatthisORGstatementis"0F00H"whichreferstothestartaddress

ofthelastpagewithinthe4KProgramMemoryofthedevice.Thetablepointerissetuphereto

haveaninitialvalueof"06H".Thiswillensurethatthefirstdatareadfromthedatatablewillbeat

theProgramMemoryaddress"0F06H"or6locationsafterthestartofthelastpage.Notethatthe

valueforthetablepointerisreferencedtothefirstaddressofthepresentpageifthe"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.

HT69F240 Datasheet(PDF) 19 Page - Holtek Semiconductor Inc

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