Microprocessor - unit 2-Addressing Modes of 8085

Microprocessor and Microcontroller-----

1. ADDRESSING MODES OF
8085

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Addressing Modes of 8085
Toperformanyoperation,wehavetogivethe
correspondinginstructionstothemicroprocessor.
Ineachinstruction,programmerhastospecify3
things:
Operationtobeperformed.
Addressofsourceofdata.
Addressofdestinationofresult.

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Addressing Modes of 8085
Themethodbywhichtheaddressof
sourceofdataortheaddressof
destinationofresultisgiveninthe
instructioniscalledAddressingModes.
Thetermaddressingmodereferstothe
wayinwhichtheoperandoftheinstruction
isspecified.

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Whyuseaddressingmodes
in8085microprocessor?
Flexibility:Addressingmodesprovideaflexible
waytoaccessdataandinstructionsinmemory.
dependingonthetypeofdatabeingaccessed,the
sizeofthedata,andotherfactors.
Memoryoptimization:Addressingmodescanhelp
tooptimizetheuseofmemoryresourcesby
allowingdataandinstructionstobeaccessedinthe
mostefficientwaypossible.

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Performanceoptimization:Addressingmodes
canalsohelptooptimizetheperformanceofthe
microprocessorbyreducingthenumberofmemory
accessesneededtofetchdataorinstructions.
Reducedcodesize:Addressingmodescanhelp
toreducethesizeofcodeneededtoperforma
particulartask.Byusingaddressingmodes
programmerscanwritemorecompactandefficient
code.

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Types of Addressing Modes
1.DirectAddressingMode
2.RegisterAddressingMode
3.RegisterIndirectAddressingMode
4.ImmediateAddressingMode
5.ImplicitAddressingMode

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Direct Addressing Mode
Inthismode,theaddressofthe
operandisgivenintheinstructionitself.
LDAistheoperation.
2500Histheaddressofsource.
Accumulatoristhedestination.
LDA2500 HLoad the contents of memory
location 2500 Hin accumulator.

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Directaddressing:Directaddressingisused
whentheaddressoftheoperandisdirectly
specifiedintheinstruction.Thisaddressing
modeisusedforsimpleoperationswherethe
operandisstoredinaspecificmemory
location,andtheaddressdoesnotneedtobe
calculatedormanipulatedinanyway.

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Register Addressing Mode
In this mode, the operand is in general
purpose register.
MOV is the operation.
B is the source of data.
A is the destination.
MOVA, BMove the contents of register B to A.

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Registeraddressing:Registeraddressing
isusedwhentheoperandisstoredina
register,ratherthaninmemory.This
addressingmodeisusefulforperforming
fastarithmeticorlogicoperationsonsmall
amountsofdata.

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Register Indirect Addressing
Mode
Inthismode,theaddressofoperandis
specifiedbyaregisterpair.
MOVistheoperation.
MisthememorylocationspecifiedbyH-L
registerpair.
Aisthedestination.
MOV A, MMove datafrom memory location
specified by H-L pair to accumulator.

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Immediate Addressing Mode
In this mode, the operand is specified
within the instruction itself.
MVI is the operation.
05 H is the immediate data (source).
A is the destination.
MVI A, 05 HMove 05H in accumulator.

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Immediate addressing:Immediate
addressingisusedwhentheoperandis
specifieddirectlyintheinstruction,rather
thanbeingstoredinmemory.This
addressingmodeisusefulforperforming
simplearithmeticorlogicoperationson
constantsorliterals.

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Implicit Addressing Mode
Ifaddressofsourceofdataaswellasaddressof
destinationofresultisfixed,thenthereisnoneedto
giveanyoperandalongwiththeinstruction.
CMAistheoperation.
Aisthesource.
Aisthedestination.
CMA Complement accumulator.

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Challenges associated with
addressingmodesinthe8085
microprocessor
Limitedaddressingrange
Complexinstructionset
Limitedaddressingmodes
Stackmanagement
Performanceconsiderations
Memorymanagement

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Advantages of Addressing Modes
in 8085 Microprocessor
Versatility
Efficientmemoryusage
Easytouse
Improvedperformance

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Disadvantages of Addressing
Modes in 8085 Microprocessor
Complexity
Debuggingdifficulties
Limitations