02 Addressing Modes

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ADDRESSING MODES &

Instruction set


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Introduction

2

8086Microprocessor

ProgramA set of instructions written to solve

a problem.

InstructionDirections which a microprocessor

follows to execute a task or part of atask.

Computer language

High Level Low Level

achine Language Assembl! Language

"inar! bits #nglish Alphabets $nemonics% Assembler

nemonics achineLanguage


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ADDRESSING MODES


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&roup I ' Addressing modes forregister and immediate data

&roup I( ' )elative Addressing mode

&roup ( ' Implied Addressing mode

&roup III ' Addressing modes forI*+ ports

&roup II ' Addressing modes formemor! data

Addressing odes

5

8086Microprocessor

#ver! instruction of a program has to operate on a data.,he different wa!s in which a source operand is denotedin an instruction are known as addressing modes.

-. )egister Addressing

. Immediate Addressing

/. Direct Addressing

0. )egister Indirect Addressing

1. "ased Addressing

2. Indexed Addressing

3. "ased Index Addressing

4. 5tring Addressing

6. Direct I*+ port Addressing

-7. Indirect I*+ port Addressing

--. )elative Addressing

-. Implied Addressing


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Addressing odes

6

8086Microprocessor





1. "ased Addressing








,he instruction will specif! the name of theregister which holds the data to be operated b!the instruction.

#xample'

+( CL8 DH

,he content of 49bit register DH is moved toanother 49bit register CL

:CL; :DH;

&roup I ' Addressing modes forregister and immediate data


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Addressing odes

7

8086Microprocessor





1. "ased Addressing








In immediate addressing mode8 an 49bit or -29bitdata is specified as part of the instruction

#xample'

+( DL8 74H

,he 49bit data :74H; given in the instruction is

moved to DL

:DL; 74H

+( A


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Addressing odes ' emor! Access

9

8086Microprocessor

7 Address lines 4742 can address up to7> - b!tes of memor!

However8 the largest register is onl! -2 bits

Ph!sical Address will have to be calculatedPh!sical Address ' Actual address of a b!te inmemor!. i.e. the value which goes out onto theaddress bus.

emor! Address represented in the form ?5eg ' +ffset :#g 9 46A"'=7-;

#ach time the processor wants to accessmemor!8 it takes the contents of a segmentregister8 shifts it one hexadecimal place to the

left :same as multipl!ing b! -2-7;8 then add there@uired offset to form the 79 bit address

46A" ' =7- 46A" 46A"7 :Paragraph to b!te 46A" x -7 > 46A"7; =7- 7=7- :+ffset is alread! in b!te unit; 9999999 64AC :,he absolute address;

16 bytes ofcontiguous memory


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Addressing odes

11

8086Microprocessor





1. "ased Addressing








Here8 the effective address of the memor!location at which the data operand is stored isgiven in the instruction.

,he effective address is Bust a -29bit numberwritten directl! in the instruction.

#xample'

+( "


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Addressing odes

12

8086Microprocessor





1. "ased Addressing








In )egister indirect addressing8 name of theregister which holds the effective address :#A;will be specified in the instruction.

)egisters used to hold #A are an! of the followingregisters'

"


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Addressing odes

13

8086Microprocessor





1. "ased Addressing








In "ased Addressing8 "< or "P is used to hold thebase value for effective address and a signed 49bitor unsigned -29bit displacement will be specified

in the instruction.

In case of 49bit displacement8 it is sign extendedto -29bit before adding to the base value.

Ehen "< holds the base value of #A8 79bitph!sical address is calculated from "< and D5.

Ehen "P holds the base value of #A8 "P and 55 isused.

#xample'

+( A


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Addressing odes

14

8086Microprocessor





1. "ased Addressing








5I or DI register is used to hold an index value formemor! data and a signed 49bit or unsigned -29bit displacement will be specified in the

instruction.

Displacement is added to the index value in 5I orDI register to obtain the #A.

In case of 49bit displacement8 it is sign extendedto -29bit before adding to the base value.

#xample'

+( C


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Addressing odes

15

8086Microprocessor





1. "ased Addressing








In "ased Index Addressing8 the effective addressis computed from the sum of a base register :" :5I; "A > :D5; x -2-7 A > "A #A

Calculation of destination memor! location'#A#> :DI; "A# > :#5; x -2-7 A#> "A# #A#

:A#; :A;

If D= > -8 then :5I; :5I; ? - and :DI; > :DI; 9 -If D= > 78 then :5I; :5I; - and :DI; > :DI; -

&roup II ' Addressing modesfor memor! data

Note : ffecti!e address oft"e #tra segment register


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Addressing odes8086

Microprocessor





1. "ased Addressing








,hese addressing modes are used to access datafrom standard I*+ mapped devices or ports.

In direct port addressing mode8 an 49bit portaddress is directl! specified in the instruction.

#xample' IG AL8 76H

+perations' P+),addr> 76H :AL; :P+),;

Content of port with address 76His

moved to AL register

In indirect port addressing mode8 the instructionwill specif! the name of the register which holdsthe port address. In 47428 the -29bit port addressis stored in the D< register.

#xample' +, D


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Addressing odes

1$

8086Microprocessor





1. "ased Addressing








In this addressing mode8 the effective address ofa program instruction is specified relative toInstruction Pointer :IP; b! an 49bit signeddisplacement.

#xample' J 7AH

+perations'

777AH 7AH :sign extend;

If J= > -8 then

#A > :IP; 777AH

"A > :C5; x -2-7A > "A #A

If J= > -8 then the program control Bumps tonew address calculated above.

If J= > 78 then next instruction of theprogram is executed.

&roup I( ' )elativeAddressing mode


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Addressing odes

19

8086Microprocessor





1. "ased Addressing








Instructions using this mode have no operands.

,he instruction itself will specif! the data to beoperated b! the instruction.

#xample' CLC

,his clears the carr! flag to Kero.

&roup I( ' ImpliedAddressing mode


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INSTRUCTION SET


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-. Data ,ransfer Instructions

. Arithmetic Instructions

/. Logical Instructions

0. 5tring manipulation Instructions

1. Process Control Instructions

2. Control ,ransfer Instructions

Instruction 5et

21

8086Microprocessor

4742 supports 2 t!pes of instructions.


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Instruction 5et

22

8086Microprocessor

Instructions that are used to transfer data* address in toregisters8 memor! locations and I*+ ports.

&enerall! involve two operands' 5ource operand andDestination operand of the same siKe.

5ource' )egister or a memor! location or an immediate dataDestination' )egister or a memor! location.

,he siKe should be a either a b!te or a word.

A 49bit data can onl! be moved to 49bit register* memor!and a -29bit data can be moved to -29bit register* memor!.


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Instruction 5et

23

8086Microprocessor

nemonics' +(8


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Instruction 5et

24

8086Microprocessor

nemonics' +(8 :55; x -2-7 5P

:A 5M A 5 -; :reg-2;

:5P; :5P; ?

A 5 > :55; x -2-7 5P

:A 5M A 5 -; :mem;

P+P reg-2* mem

P+P reg-2

P+P mem

A 5 > :55; x -2-7 5P

:reg-2; :A 5M A 5 -;

:5P; :5P;

A 5 > :55; x -2-7 5P

:mem; :A5M A

5 -;

:5P; :5P;

8086


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Instruction 5et

25

8086Microprocessor

nemonics' +(8


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Instruction 5et

26

8086Microprocessor

nemonics' ADD8 ADC8 5"8 5""8 IGC8 D#C8 L8 DI(8 CP

ADD reg* mem8 reg-*mem

ADC reg8 reg-

ADC reg8 mem

ADC mem8 reg-

:reg; :reg-; :reg;

:reg; :reg; :mem;

:mem; :mem;:reg-;

ADD reg*mem8 data

ADD reg8 data

ADD mem8 data:reg; :reg; data

:mem; :mem;data

ADD A8 data

ADD AL8 data4ADD A


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Instruction 5et

27

8086Microprocessor


ADC reg* mem8 reg-*mem

ADC reg8 reg-

ADC reg8 mem

ADC mem8 reg-

:reg; :reg-; :reg;C=

:reg; :reg; :mem;C=

:mem; :mem;:reg-;C=

ADC reg*mem8 data

ADC reg8 dataADC mem8 data

:reg; :reg; dataC=

:mem; :mem;dataC=

ADDC A8 data

ADD AL8 data4

ADD A


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Instruction 5et

2$

8086Microprocessor


5" reg* mem8 reg-*mem

5" reg8 reg-

5" reg8 mem

5" mem8 reg-

:reg; :reg-; 9 :reg;

:reg; :reg; 9 :mem;

:mem; :mem; 9 :reg-;

5" reg*mem8 data

5" reg8 data

5" mem8 data:reg; :reg; 9 data

:mem; :mem; 9 data

5" A8 data

5" AL8 data45" A


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Instruction 5et

29

8086Microprocessor


5"" reg* mem8 reg-*mem

5"" reg8 reg-

5"" reg8 mem

5"" mem8 reg-

:reg; :reg-; 9 :reg; 9 C=

:reg; :reg; 9 :mem;9 C=

:mem; :mem; 9 :reg-; ?C=

5"" reg*mem8 data

5"" reg8 data5"" mem8 data

:reg; :reg; ? data 9 C=

:mem; :mem; 9 data 9 C=

5"" A8 data

5"" AL8 data4

5"" A


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Instruction 5et

3%

8086Microprocessor


IGC reg* mem

IGC reg4

IGC reg-2

IGC mem

:reg4; :reg4; -

:reg-2; :reg-2; -

:mem; :mem; -

D#C reg* mem

D#C reg4

D#C reg-2

D#C mem

:reg4; :reg4; 9 -

:reg-2; :reg-2; 9 -

:mem; :mem; 9 -

8086


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Instruction 5et

31

8086Microprocessor


L reg* mem

L reg

L mem

=or b!te ' :A


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Instruction 5et

32

8086Microprocessor


DI( reg* mem

DI( reg

DI( mem

=or -29bit '9 49bit '

:AL; :A


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Instruction 5et

33

8086Microprocessor


IDI( reg* mem

IDI( reg

IDI( mem

=or -29bit '9 49bit '

:AL; :A


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Instruction 5et

34

8086Microprocessor


CP reg*mem8 reg-* mem

CP reg8 reg-

CP reg8 mem

CP mem8 reg-

odif! flags :reg; ? :reg-;

If :reg; O :reg-; then C=>78 J=>78 5=>7

If :reg; :reg-; then C=>-8 J=>78 5=>-If :reg; > :reg-; then C=>78 J=>-8 5=>7

odif! flags :reg; ? :mem;

If :reg; O :mem; then C=>78 J=>78 5=>7If :reg; :mem; then C=>-8 J=>78 5=>-

If :reg; > :mem; then C=>78 J=>-8 5=>7

odif! flags :mem; ? :reg-;

If :mem; O :reg-; then C=>78 J=>78 5=>7

If :mem; :reg-; then C=>-8 J=>78 5=>-

If :mem; > :reg-; then C=>78 J=>-8 5=>7

8086


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Instruction 5et

35

8086Microprocessor


CP reg*mem8 data

CP reg8 data

CP mem8 data

odif! flags :reg; ? :data;

If :reg; O data then C=>78 J=>78 5=>7

If :reg; data then C=>-8 J=>78 5=>-If :reg; > data then C=>78 J=>-8 5=>7

odif! flags :mem; ? :mem;

If :mem; O data then C=>78 J=>78 5=>7

If :mem; data then C=>-8 J=>78 5=>-

If :mem; > data then C=>78 J=>-8 5=>7

8086


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Instruction 5et

36

8086Microprocessor


CP A8 data

CP AL8 data4

CP A78 J=>78 5=>7

If :AL; data4 then C=>-8 J=>78 5=>-If :AL; > data4 then C=>78 J=>-8 5=>7

odif! flags :A78 5=>7

If :mem; data-2 then C=>-8 J=>78 5=>-

If :mem; > data-2 then C=>78 J=>-8 5=>7

i 58086


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Instruction 5et

37

8086Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

3$

8086Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

39

8086Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

4%

8086Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

41

8086Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

42

8086Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

43

Microprocessor

nemonics' AGD8 +)8


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Instruction 5et

44

Microprocessor

nemonics' AGD8 +)8


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0. 5tring anipulation Instructions

Instruction 5et

45

Microprocessor

5tring ' 5e@uence of b!tes or words

4742 instruction set includes instruction for string movement8 comparison8scan8 load and store.

)#P instruction prefix ' used to repeat execution of string instructions

5tring instructions end with 5or 5"or 5E.5represents string8 5"string b!te and 5Estring word.

+ffset or effective address of the source operand is stored in 5Iregister andthat of the destination operand is stored in DIregister.

Depending on the status of D=8 5Iand DIregisters are automaticall!updated.

D= > 7 5I and DI are incremented b! - for b!te and for word.

D= > - 5I and DI are decremented b! - for b!te and for word.

Instruction 5et8086


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Instruction 5et

46

Microprocessor

nemonics' )#P8 +(58 CP58 5CA58 L+D58 5,+5

)#P

)#PJ* )#P#

:)epeat CP5 or 5CA5 untilJ= > 7;

)#PGJ* )#PG#

:)epeat CP5 or 5CA5 until

J= > -;

Ehile C< 7 and J= > -8 repeat execution of

string instruction and

:C


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Instruction 5et

47

Microprocessor


+(5

+(5"

+(5E

A > :D5; x -2-7 :5I;

A#> :#5; x -2-7 :DI;

:A#; :A;

If D= > 78 then :DI; :DI; -M :5I; :5I;

-

If D= > -8 then :DI; :DI; 9 -M :5I; :5I; 9 -

A > :D5; x -2-7 :5I;

A#> :#5; x -2-7 :DI;

:A#M A# -; :AM A -;

If D= > 78 then :DI; :DI; M :5I; :5I;

> 9 9

Instruction 5et8086


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Instruction 5et

4$

Microprocessor


CP5

CP5"

CP5E

A > :D5; x -2-7 :5I;

A#> :#5; x -2-7 :DI;

odif! flags :A; 9 :A#;

If :A; O :A#;8 then C= > 7M J= > 7M 5= > 7

If :A; :A#;8 then C= > -M J= > 7M 5= > -

If :A; > :A#;8 then C= > 7M J= > -M 5= > 7

=or b!te operation

If D= > 78 then :DI; :DI; -M :5I; :5I;

-

If D= > -8 then :DI; :DI; 9 -M :5I; :5I; 9 -

=or word operation

If D= > 78 then :DI; :DI; M :5I; :5I;

> 9 9

Compare two string b!te or string word

Instruction 5et8086


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Instruction 5et

49

Microprocessor


5CA5

5CA5"

5CA5E

A#> :#5; x -2-7 :DI;

odif! flags :AL; 9 :A#;

If :AL; O :A#;8 then C= > 7M J= > 7M 5= > 7If :AL; :A#;8 then C= > -M J= > 7M 5= > -

If :AL; > :A#;8 then C= > 7M J= > -M 5= > 7

If D= > 78 then :DI; :DI; -

If D= > -8 then :DI; :DI; ? -

A#> :#5; x -2-7 :DI;

odif! flags :AL; 9 :A#;

If :A 7M J= > 7M 5= > 7

If :A -M J= > 7M 5= > -

If :A :A#

M A#

-;8 then C= > 7M J= > -M 5= > 7

5can :compare; a string b!te or word with accumulator

Instruction 5et8086


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Instruction 5et

5%

Microprocessor


L+D5

L+D5"

L+D5E

A > :D5; x -2-7 :5I;

:AL; :A;

If D= > 78 then :5I; :5I; -

If D= > -8 then :5I; :5I; ? -

A > :D5; x -2-7 :5I;

:A 78 then :5I; :5I;

If D= > -8 then :5I; :5I; ?

Load string b!te in to AL or string word in to A

Documents

02 Addressing Modes