1.ADDRESSING MODES OF 8086.ppt

Addressing modes of 8086

1. ADDRESSING MODES
EC8552-COMPUTER ARCHITECTRE &
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2. Address & Addressing Modes
Thedifferentwaysinwhichasource
operandisdenotedinaninstructionis
knownasaddressingmodes.
Thereare8differentaddressingmodes.
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3. Addressing Modes
Register addressing mode
Immediate addressing mode
Direct addressing mode
Register indirect addressing mode
Based addressing mode
Indexed addressing mode
Based-index addressing mode
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4. Register Addressing Mode
It means that the register is the source of
an operand for an instruction.
Example
MOV CX, AX ; copies the contents of the
16-bit AX register into ; the 16-bit CX
register),
ADD BX, AX
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5. Immediate Addressing Mode
Theaddressingmodeinwhichthedata
operandisapartoftheinstructionitselfis
knownasimmediateaddressingmode.
Example
MOVCX,4929H,
ADDAX,2387H,
MOVAL,FFH
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6. Direct Addressing Mode
Theaddressingmodeinwhichthe
effectiveaddressofthememorylocation
iswrittendirectlyintheinstruction.
Example
MOVAX,[1592H],
MOVAL,[0300H]
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7. Register Indirect Addressing
Mode
Thisaddressingmodeallowsdatatobe
addressedatanymemorylocation
throughanoffsetaddressheldinanyof
thefollowingregisters:BP,BX,DI&SI.
Example
MOVAX,[BX];SupposetheregisterBX
contains4895H,thenthecontents;
4895HaremovedtoAX
ADDCX,{BX}
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8. Based Addressing Mode
Inthisaddressingmode,theoffset
addressoftheoperandisgivenbythe
sumofcontentsoftheBX/BPregisters
and8-bit/16-bitdisplacement.
Example
MOVDX,[BX+04],
ADDCL,[BX+08]
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9. Indexed Addressing Mode
Inthisaddressingmode,theoperands
offsetaddressisfoundbyaddingthe
contentsofSIorDIregisterand8-bit/16-
bitdisplacements.
Example
MOVBX,[SI+16],
ADDAL,[DI+16]
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10. Based-Index Addressing Mode
Inthisaddressingmode,theoffset
addressoftheoperandiscomputedby
summingthebaseregistertothecontents
ofanIndexregister.
Example
ADDCX,[AX+SI],
MOVAX,[AX+DI]
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11. Based Indexed with Displacement
Mode
Inthisaddressingmode,theoperands
offsetiscomputedbyaddingthebase
registercontents.AnIndexregisters
contentsand8or16-bitdisplacement.
Example
MOVAX,[BX+DI+08],
ADDCX,[BX+SI+16]
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