微机系统与接口ch4new

Chapter4:DataMovementInstructionsIntroduction

Thischapterconcentratesonthedatamovementinstructions.ThedatamovementinstructionsincludeMOV,PUSH,POP,XCHG,XLAT,IN,OUT,LEA,LDS,LES,LAHF,SAHF.Stringinstructions:MOVS,LODS,STOS,Contents

4–1MOVRevisited4–2PUSH/POP4–3Load-EffectiveAddress4–4StringDataTransfers4–5MiscellaneousDataTransferInstructions4–1

MOVRevisitedMicrosoftMACROassembler(MASM)Intel

Assembler(ASM)BorlandTurboassembler(TASM)COPYMOVdst，src ;(dst)←(src)Dst:R,M,SR；Src:R,M,SR,ImRegImSRMMOVDX，BP ；MOVAX，ES ；MOVSP，1800H ；MOVBL，[2480H] ；MOVDS，[BX＋DI] ；MOVBYTEPTR[SI]，0FH ；4–1

MOVRevisited4–2

PUSH/POPImportantinstructionsthatstoreandretrievedatafromtheLIFO(last-in,first-out)stackmemory.SixformsofthePUSHandPOPinstructions:register,memory,immediatesegmentregister,flags,allregistersImmediateaddressingallowsimmediatedatatobepushedontothestack,butnotpoppedoffthestack.4–2

PUSH/POP71、PUSHPUSHCX ；regPUSHDS ；segPUSH[0040H]

；memSP-22、POPPOPSI ；regPOPES ；segPOP[BX] ；memSP+2CS,No！第2节8086/8088指令系统4–2

PUSH/POPSegmentregisterCSmaybepushed,butdatafromthestackmayneverbepoppedintoCSTheflagsmaybepushedorpoppedfrom

thatstack.contentsofallregistersmaybepushedor

poppedAlwaystransfers2bytesofdatatothestack;PUSHF(pushflags)instructioncopiesthecontentsoftheflagregistertothestack.PUSHSS=3200H，SP=0800H，AX=105CH。SP=0800H→32800H……StackPUSHAXSP=SP－1→327FFHSP=SP－1→327FEHSP＝07FEH5CHAL10HAHPUSHFigure4–13

TheeffectofthePUSHAXinstructiononESPandstackmemorylocations37FFHand37FEH.Thisinstructionisshownatthepointafterexecution.

PUSHPUSHCX ；RPUSHDS ；SRPUSH[0040H]；MPOPPerformstheinverseoperationofPUSH.POPremovesdatafromthestackandplacesitinatarget16-bitregister,segmentregister,ora16-bitmemorylocation.notavailableasanimmediatePOP POPF(popflags)removesa16-bitnumberfromthestackandplacesitintheflagregister;SS=3200H，SP=07FEHSP=SP+1→32800HPOPAXSP=SP+1→327FFHSP=07FEH→327FEH……Stack10H5CHSP＝0800HAX＝105CHAHALLIFOPOPFigure4–15

ThePOPBXinstruction,showinghowdataareremovedfromthestack.Thisinstructionisshownafterexecution.

POPPOPSI ；RPOPES ；SRPOP[BX] ；M4–3

LOADEFFECTIVEADDRESSLEAinstructionloadsany16-or32-bitregisterwiththeoffsetaddressLDSandLESloada16-bitregisterwithoffsetaddressretrievedfromamemorylocationthenloadeitherDSorESwithasegment

addressretrievedfrommemory4–3

LOADEFFECTIVEADDRESSLEA16-bitR，MLDS16-bitR，MLES16-bitR，MLEALoadsa16-bitregisterwiththeoffsetaddressofthedataspecifiedbytheoperand.LEA；MOVwithOFFSET

LEABX,[DI]MOVBX,OFFSET[DI]LDS,LESLoadany16-or32-bitregisterwithanoffset

address,andtheDS,ES,segmentregisterwithasegmentaddress.instructionsuseanymemory-addressingmodes

toaccessa32-bitmemorysectionthatcontainbothsegmentandoffsetaddressFigure4–17

TheLDSBX,[DI]instructionloadsregisterBXfromaddresses11000Hand11001HandregisterDSfromlocations11002Hand11003H.ThisinstructionisshownatthepointjustbeforeDSchangesto3000HandBXchangesto127AH.

LDS,LESThisinstructiontransfersthe32-bitnumber,addressedbyDIinthedatasegment,into

theBXandDSregisters.LDS,LESinstructionsobtainanewfaraddressfrommemory.offsetaddressappearsfirst,followedbythesegmentaddress Thisformatisusedforstoringall32-bitmemoryaddresses.LDS,LES4–4

STRINGDATATRANSFERSSTRING?Fivestringdatatransferinstructions:LODS,STOS,MOVS.Eachallowsdatatransfersasasinglebyte,word,ordoubleword.Beforethestringinstructionsarepresented,theoperationoftheDflag-bit(direction),DI,andSImustbeunderstoodastheyapplytothestringinstructions.4–4

STRINGDATATRANSFERSTheDirectionFlagThedirectionflag(D,locatedintheflagregister)selectstheauto-incrementortheauto-decrementoperationfortheDIandSIregistersduringstringoperations.usedonlywiththestringinstructionsTheCLDinstructionclearstheDflagandtheSTDinstructionsetsit.CLD(DF=0)instructionselectstheauto-incrementmodeandSTD(DF=1)selectstheauto-decrementmodeDIandSIDuringexecutionofstringinstruction,memoryaccessesoccurthroughDIandSIregisters.DIoffsetaddressaccessesdataintheextrasegmentforallstringinstructionsthatuseitSIoffsetaddressaccessesdatabydefault

inthedatasegment

DS:SI——Source；changedbyasegmentoverrideprefixES:DI——Target;neverchangedLODSSOURCELABELLODSB：AL←(DS:SI)，SI←SI±1LODSW：AX←(DS:SI)

，SI←SI±2LODSLODSLoadsAL,AXwithdataatsegmentoffsetaddressindexedbytheSIregister.Figure4–18

TheoperationoftheLODSWinstructionifDS=1000H,D=0,11000H,11001H=A0.ThisinstructionisshownafterAXisloadedfrommemory,butbefore

SIincrementsby2.

STOSStoresAL,AX

attheextrasegmentmemorylocationaddressedbytheDIregister.STOSB(storesabyte)storesthebyteinALattheextrasegmentmemorylocationaddressedbyDI.STOSW(storesaword)storesAXinthememorylocationaddressedbyDI.Afterthebyte(AL),word(AX)isstored,contentsofDIincrementordecrement.

STOSTARGETLABEL

STOSB：(ES:DI)←AL，DI←DI±1STOSW：(ES:DI)←AX，DI←DI±2STOSREPNZ/REPNESTRINSTRUCTIONRepeatwhileNotEqual/NotZero),UNTILLZF＝1

ORCX＝0REP/REPNZ/REPNESTOSwithaREP

Therepeatprefix(REP)isaddedtoanystringdatatransferinstructionexceptLODS.REPSTOSREPprefixcausesCXtodecrementby1eachtimethestringinstructionexecutes;afterCXdecrements,thestringinstructionrepeatsIfCXreachesavalueof0,theinstructionterminatesandtheprogramcontinues.IfCXisloadedwith100andaREPSTOSBinstructionexecutes,themicroprocessorautomaticallyrepeatstheSTOSB100times.27UppercasetoLowercase,thenstoreinthetarget：

MOVCX,40 ；count

LEASI,STR1 ；SI,source(DS)

LEADI,STR2 ；DI,target(ES)

CLD

；DF=0，IncreaseAGN: LODSB ；toAL

ADD AL,‘a’－‘A’

；→

STOSB ；store

LOOPAGN ；loop

……MOVSTransfersabyte,wordadatasegmentaddressedbySItoextrasegmentlocationaddressedbyDI.Thedestinationoperand(DI)mustalwaysbelocatedintheextrasegment.MOVSB,MOVSWREPMOVS

;transferuntilCX=0MOVSDI，SIMOVSB；(ES:DI)←(DS:SI)，SI←SI±1，DI←DI±1MOVSW；(ES:DI)←(DS:SI)，SI←SI±2，DI←DI±2MemorySOURCETARGETMemoryCOURCETARGETMOVSMOVCX,10H ；COUNTLEA SI,STR1 ；STR1：SOUCEADDSI,30

；ENDOFSTR1LEADI,STR2 ；STR2：TARGETADDDI,30

；ENDOFTARGETSTD ；DF=1，DECREACEREPMOVSW ；16WORDSTRANSFERMOV?WORD-STRINGTRANSFER：MOVS4–5

MISCELLANEOUSDATATRANSFERINSTRUCTIONSXCHG,LAHF,SAHF,XLAT,IN,OUTXCHGExchangescontentsofaregisterwithanyotherregisterormemorylocation.cannotexchangesegmentregistersXCHGop1,op2；(op1)

(op2)op1:R,M；op2:R,MREGMEMLAHFandSAHFLAHFinstructiontransferstherightmost8bitsoftheflagregisterintotheAHregister.SAHFinstructiontransferstheAHregisterintotherightmost8bitsoftheflagregister.34LAHF(Flags)L→AHSAHFAH→(Flags)LPUSHF

POPF

Hidden唯一可改变TF的指令！第2节8086/8088指令系统TF

1POPF ;(SS:SP)→FlagsPUSHF ;Flags→(SS:SP)MOVBP,SPMOV[BP+1],01HOR[BP+1],01H;←BPSS:0000HSP→(Flags)L(Flags)H←BP+101H————ODITSZ—A—P—C1514131211109876543210Flags：(Flags)H(Flags)LXLATConvertsthecontentsoftheALregisterintoanumberstoredinamemorytable.performsthedirecttablelookuptechniqueoftenusedtoconvertonecodetoanotherAnXLATinstructionfirstaddsthecontentsofALtoBXtoformamemoryaddresswithinthedatasegment.copiesthecontentsofthisaddressintoALonlyinstructionaddingan8-bittoa16-bitnumberFigure4–19

TheoperationoftheXLATinstructionatthepointjustbefore6DHisloadedintoAL.

XLAT38TABDB0,1,4,9,16,25,36,49,64,81；……MOVBX，OFFSETTABMOVAL，4XLATTABAL＝16。XLATINandOUTIN&OUTinstructionsperformI/OoperationsContentsofAL,AXaretransferredonlybetweenI/Odeviceandmicroprocessor.anINinstructiontransfersdatafromanexternalI/OdeviceintoAL,AXanOUTtransfersdatafromAL,AXtoanexternalI/OdeviceTwoformsofI/Odevice(port)addressing:Fixed-portaddressingallowsdatatransferbetweenAL,AXusingan8-bitI/Oportaddress.(portnumber)Variable-portaddressingallowsdatatransfersbetweenAL,AX,anda16-bitportaddress.theI/OportnumberisstoredinregisterDX,

INandOUTFigure4–20

Thesignalsfoundinthemicroprocessor-basedsystemforanOUT19H,AXinstruction.

INandOUT4–6

SEGMENTOVERRIDEPREFIXMaybeaddedtoalmostanyinstructioninanymemory-addressingmodeallowstheprogrammertodeviatefromthe

defaultsegmentonlyinstructionsthatcannotbeprefixedarejumpandcallinstructionsusingthecodesegmentregisterforaddressgenerationAdditionalbyteappendedtothefrontofaninstructiontoselectalternatesegmentregisterMOVAL,[DI];DS:[DI]MOVAL,ES:[DI]4–6

SEGMENTOVERRIDEPREFIX4–7

ASSEMBLERDETAILTheassemblercanbeusedtwoways:withmodelsuniquetoaparticularassemblerwithfull-segmentdefinitionsthatallowcompletecontrolovertheassemblyprocessandareuniversaltoallassemblersDirectivesTheDB(definebyte)directivestoresbytesofdatainthememory.BYTEPTRindicatesthesizeofthedatareferencedbyapointerorindexregister.ComplexsectionsofassemblycodearestillwrittenusingMASM.StoringDatainaMemorySegment

DB(definebyte),DW(defineword),andDD(definedoubleword)aremostoftenusedwithMASMtodefineandstorememorydata.Ifanumericcoprocessorexecutessoftwareinthesystem,theDQ(definequadword)andDT(definetenbytes)directivesarealsocommon.Thesedirectiveslabelamemorylocationwithasymbolicnameandindicateitssize.

DA1DB10H,52HDA2DW1122H,34HDA3DD5*20H,0FFEEH

StoringDatainaMemorySegment

FIRSTDB‘HELLO’；SECONDDW‘OK’；StoringDatainaMemorySegment

M1DB?

；M2DW0D55H，?

；ONEDB5DUP(0)TWODW10DUP(?)THREEDB4DUP(1，2DUP(20H))THREE：howmanybytes?THREE-ONE=????StoringDatainaMemorySegment

OPE1DB1，2OPE2DW2233H，5566H

MOVAX，OPE1+1;????MOVAL，OPE2;???????

MOVAX，WORDPTROPE1+1；

MOVAL，BYTEPTROPE2；AX＝3302HAL＝33HStoringDatainaMemorySegment

ASSUME,EQU,andORG

Equatedirective(EQU)equatesanumeric,ASCII,orlabeltoanotherlabel.equatesmakeaprogramclearerandsimplifydebuggingTheTHISdirectivealwaysappearsasTHISBYTE,THISWORD,THISDWORD,orTHISQWORD.Theassemblercanonlyassigneitherabyte,word,ordoublewordaddresstoalabel.

COUNTEQU100；DATAEQUCOUNT＋2；A1EQU[DX＋SI]；B1EQUOFFSETA1；C1EQUADD；COUNT＝100COUNT＝COUNT＋10A1＝BX＋SIMOVAX,[A1]；B1＝ADDA1＝BXMOVCX,[A1]ASSUME,EQU,andORG

ASSUMEASAUMECS:cseg_name，DS:dseg_name，SS:sseg_name，ES:eseg_nameASSUME,EQU,andORG

Proc_namePROC属性;

……；

RET[N]Proc_nameENDPPROCandENDP

ThePROCdirective,whichindicatesthestartofaprocedure,mustalsobefollowedwithaNEARorFAR.

ANEARprocedureisonethatresidesinthesamecodesegmentastheprogram,oftenconsideredtobelocal

AFARproceduremayresideatanylocationinthememorysystem,consideredglobal

PROCandENDP

SEGMENT/ENDSseg_name

SEGMENT ……….seg_name

ENDSFull-SegmentDefinitionsMYDATA SEGMENT X DB ? Y DW ? Z DD ?MYDATA ENDSMYEXTRA SEGMENT ALPHA DB ? BETA DW ? GAMMA DD ?MYEXTRA ENDSMYSTACK SEGMENT DW 100DUP(?) TOP EQU THIS WORDMYSTACK ENDSFull-SegmentDefinitions my_codesegment

assumecs:my_code,ds:my_data,ss:ss_seg mainprocfar ……Full-SegmentDefinitionsMYCODE SEGMENTASSUMECS:MYCODE,DS:MYDATA,ES:MYEXTRA,SS:MYSTACKSTART: MOV AX,MYDATA ; 或MOV AX,SEGX MOV DS,AX MOV AX,MYEXTRA ;或MOVAX,SEGALPHA MOV ES,AX MOV AX,MYSTACK ; MOV SS,AX MOV SP,OFFSETTOP ………………MYCODE ENDS END STARTFull-SegmentDefinitionsDATA SEGMENT ;D1 DB5DUP（？） ;CC EQU$－D1 ;SUM DW0 ;DATA ENDS ;STACKSEGMENTPARASTACK‘STACK’

;

DB100DUP（？）

;STACK ENDS

;CODE SEGMENT

;

ASSUMEDS:DATA，SS:STACK，CS:CODE;BEGIN：MOVAX，DATA ;

MOVDS，AX LEASI，D1 ;定义存储单元的数据伪指令定义堆栈段定义语句指令

MOVCX，CC+1 ；预置次数

LODSBYTEPTR[SI] ；取一个数并修改指针

DECCX ；修改次数

MOVAH，0 ；清AX的高字节

CLC ；清CF位AGAN：ADCSUM，AX ；累加

LODSBYTEPTR[SI] ；再取数并修改指针

LOOPAGAN ；控制循环

MOVAH，4CH ；完成，返回DOS INT21HCODE ENDS

；代码段结束

END BEGIN ；整个程序结束段定义汇编程序结束SUMMARYDatamovementinstructionstransferdatabetweenregisters,aregisterandmem-ory,aregisterandthestack,memoryandthestack,theaccumulatorandI/O,andtheflagsandthestack.Memory-to-memorytransfersareallowedonlywiththeMOVSinstruction.SUMMARYDatamovementinstructionsincludeMOV,PUSH,POP,XCHG,XLAT,IN,OUT,LEA,LDS,LES,LAHF,SAHF,andthefollowingstringinstruc-tions:LODS,STOS,MOVS.Thefirstbyteofaninstructioncontainstheopcode,whichspecifiestheoperationperformedbythemicroprocessor.Theopcodemaybeprecededbyoneormoreoverrideprefixes.(cont.)SUMMARYLEA,LDS,andLESinstructionsloadaregisterorregisterswithaneffectivead-dress.TheLEAinstructionloadsany16-bitregisterwithaneffectiveaddress;LDSandLESloadany16-bitregisterandeitherDSorESwiththeeffectiveaddress.(cont.)SUMMARYThedirectionflag(D)choosestheauto-incrementorauto-decrementmodeofop-erationforDIandSIforstringinstructions.ToclearDto0,usetheCLDinstructiontoselecttheauto-incrementmode;tosetDto1,usetheSTDinstructiontoselect