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ADDRESSING MODES OF 8085. Ad d ressing Modes of 8085. T o p e rform a n y op e rat i o n , we h a ve to g i ve t h e corres p o n d i ng i n structi o ns to the micro p rocesso r . In e a ch instr u ctio n , pr o gr a m m er h a s t o speci f y 3 t h i n gs: Ope r at i on to be p erfo rm ed.
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AddressingModesof8085 • Toperformany operation,wehave to givethecorrespondinginstructionsto themicroprocessor. • Ineachinstruction,programmerhas to • specify3things: • Operationtobeperformed. • Addressofsourceofdata. • Addressofdestinationofresult.
AddressingModesof8085 • Themethod by whichtheaddressof sourceof dataortheaddressof destinationofresultis givenin the instructioniscalledAddressing Modes. • Thetermaddressingmoderefersto thewayinwhichtheoperandofthe instructionisspecified.
TypesofAddressingModes • Intel8085usesthefollowing • addressingmodes: • DirectAddressingMode • RegisterAddressingMode • RegisterIndirectAddressingMode • ImmediateAddressingMode • ImplicitAddressingMode
DirectAddressingMode • Inthis mode,theaddressofthe operandis givenintheinstruction itself. LDA2500H Loadthecontents of memory location2500H inaccumulator. • LDAis theoperation. • 2500His theaddressofsource. • Accumulatoris thedestination.
RegisterAddressingMode • Inthis mode,theoperandisin general • purposeregister. Movethecontents ofregisterB to A. MOVA,B • MOVis theoperation. • Bis thesourceofdata. • Ais thedestination.
Register IndirectAddressing Mode • Inthis mode,theaddressofoperand • isspecifiedbyaregisterpair. MOVA,M Movedatafrommemorylocation specifiedbyH-Lpair to accumulator. • MOVis theoperation. • Misthememory locationspecifiedby • H-Lregisterpair. • Ais thedestination.
ImmediateAddressingMode • Inthis mode,theoperandisspecified • withintheinstructionitself. MVI A, 05 H Move05 H inaccumulator. • MVIis theoperation. • 05His theimmediatedata(source). • Ais thedestination.
ImplicitAddressingMode • Ifaddress of sourceof dataas wellas addressof destinationofresultis fixed, thenthere is noneedto giveany operandalongwiththe instruction. • CMA Complement accumulator. • CMAis the operation. • Aisthesource. • Ais the destination.