data movement instructions in microprocessor 8086/8088 · the operand can be a constant, memory...

Prof. Munish Vashishath

Department of Electronics Engineering

J.C.Bose University of Science & Technology

YMCA,Faridabad

Data Movement Instructions

in Microprocessor

8086/8088

Objectives of Data Movement

Instructions in Microprocessor 8086/8088

Upon completion of this chapter, you will be able to:

Explain the operation of each data movement

instruction with applicable addressing modes.

Select the appropriate assembly language

instruction to accomplish a specific data

movement task.

Data Movement Instructions in

Microprocessor 8086/8088

These instructions are used to transfer

data from source to destination.

The operand can be a constant, memory

location, register or I/O port address.

8-bit 8-bit 8-bit

O P C O D E O P E R A N D

1 byte 1 to 2 byte


MOV

❖MOV Des, Src❖ Src operand can be register, memory location or

immediate operand.

❖ Des can be register or memory operand.

❖ Both Src and Des cannot be memory location at

the same time.

❖ Example:

MOV CX, 037AH

MOV AL, BL

MOV BX, [0301H]


MOV

MOV Des, Src

0727H

0726H

0725H

0724H

0723H

0722H

Example: DS=ACDEH, SI=0724H

MOV AX, [SI]

072CH

072BH

072AH

0729H

0728H

AD5F4H

AD5F3H

AD5F2H

AD5FCH

AD5FBH

AD5FAH

AD5F9H

AD5F8H

AD5F7H

AD5F6H

AD5F5H

18H

A3H

7EH

69H

AAH

2EH

00H

55H

02H

72H

11H

❖ Physical Address

= ACEDx10H + 0724H

= AD5F4H, AD5F5H

AX=5502H

55 02

AH AL


PUSH and POP

PUSH and POP Instructions

❖ Both are important to store and retrieve data

from the LIFO structure (stack).

❖ PUSH Operand

❖ It pushes the operand into top of stack.

❖ Example:

PUSH BX

❖ POP Des

❖ It pops the operand from top of stack to Des.

❖ Example:

POP AX


PUSH

PUSH:

In 8088 and 8086 PUSH always transfer 2 bytes of data to the stack.

It has the following syntax:

PUSH src

Src could be any 2 byte register or memory location or immediate value.


PUSH

How does PUSH executes?

Simply when we push 2 bytes of data to the stack, the most significant byte is stored in stack segment pointed to by SP-1, and the least significant to location pointed by SP-2, see the following example

Example:

Let AX=31F2H, SP=100H, SS=2000H,

CX=FFFFH, BX=413AH


PUSH

31 F2

AX F2

31

Least Significant Byte

Most Significant Byte

SS:SP-2 =2000:00FEH

SS:SP-1 =2000:00FFH

SS:SP =2000:0100H

PUSH AX

SS:[SP-1] ← AH, 1st(most significant) byte.

SS:[SP-2] ← AL, 2nd(least significant) byte.

After PUSH operation, SP ← SP - 2


PUSH

The effect of the PUSH AX instruction on SP and stack

memory locations 37FFH and 37FEH. AX=6AB3H


POP

How does POP executes?

❖POP : performs the inverse operation of PUSH

❖POP : removes data from stack and place it into

target 16-bit register.

POP BX

❖BL ← SS:[SP]

❖BH ← SS:[SP+1]

❖after POP operation, SP← SP+2

POP CS ; is not a valid instruction


POP

DF 54

54

DF

SS:SP =3000:0100H

Least Significant Byte

Most Significant Byte

SS:SP+2 =3000:0102H

SS:SP+1 =3000:0101H

POP BX

BL ← SS:[SP]

BH ← SS:[SP+1]

After POP operation, SP ← SP + 2

BX


POP

Example:

Let BX=DF54H, SP=100H, SS=3000H

POP BX

BL=54 H at SP=0100H

BH=DF at SP+1=0101H

After POP operation, SP← SP+2=0102H


POP

The POP BX instruction, showing how data

are removed from the stack. POP BX


PUSH

Example:

Let

AX=31F2H

SP=072AH

SS=ACEDH

CX=FF67H

BX=413AH

PUSH AX

PUSH BX

PUSH CXSS:SP-2 =ACED:0728

SS:SP-1 =ACED:0729

CH CL

67FF

31 F2

AH AL

41 3A

BH BL

SS:SP-4 =ACED:0726

SS:SP-3 =ACED:0727

SSololuuttiionon::

SS:SP-6 =ACED:0724

SS:SP-5 =ACED:0725

SS:SP =ACED:072A


PUSH

0727H

0726H

0725H

0724H

0723H

0722H

072CH

072BH

072AH

0729H

0728H

AD5F4H

AD5F3H

AD5F2H

AD5FCH

AD5FBH

AD5FAH

AD5F9H

AD5F8H

AD5F7H

AD5F6H

AD5F5H

18H

A3H

7EH

69H

AAH

2EH

00H

55H

02H

72H

11H

0727H

0726H

0725H

0724H

0723H

0722H

072CH

072BH

072AH

0729H

0728H

AD5F4H

AD5F3H

AD5F2H

AD5FCH

AD5FBH

AD5FAH

AD5F9H

AD5F8H

AD5F7H

AD5F6H

AD5F5H

18H

A3H

7EH

31H

F2H

41H

3AH

FFH

67H

72H

11H

before after

Stack Stack


PUSH BX

•The high-order 8 bits are placed in the location addressed by SP – 1

•The low-order 8 bits are placed in the location addressed by SP – 2

•After the data are stored by a PUSH, the contents of the SP register

decremProef.nFatytezbF.yM. tEtlw-Soouosy

Prof. Fayez F. M. El-Sousy


POP

Example:

Let

SP=0724H

SS=ACEDH

POP CX

POP BX

POPAX

SS:SP+4 =ACED:0728

SS:SP+5 =ACED:0729

CH CL

67FF

31 F2

AH AL

41 3A

BH BL

SS:SP+2 =ACED:0726

SS:SP+3 =ACED:0727

SS:SP =ACED:0724

SS:SP+1 =ACED:0725

Prof. Fayez F. M. El-Sousy


POP

0727H

0726H

0725H

0724H

0723H

0722H

072CH

072BH

072AH

0729H

0728H

AD5F4H

AD5F3H

AD5F2H

AD5FCH

AD5FBH

AD5FAH

AD5F9H

AD5F8H

AD5F7H

AD5F6H

AD5F5H

67H

18H

A3H

7EH

31H

F2H

41H

3AH

FFH

11H

72H

StackSS:SP+4 =ACED:0728

SS:SP+5 =ACED:0729

CH CL

67FF

31 F2

AH AL

41 3A

BH BL

SS:SP+2 =ACED:0726

SS:SP+3 =ACED:0727

SS:SP =ACED:0724

SS:SP+1 =ACED:0725

Solution:


POP CX

•The low-order 8 bits are removed from the location addressed by SP.

•The high-order 8 bits are removed from the location addressed by

SP+1•The SPProf. Fraeyegz Fi.sMt. Eel-rSouissy incremented by 2


LEA

❖ Load-Effective Address (LEA)

❖ LEA stands for load effective address.

LEA Register, Src

❖ It loads a 16-bit register with the offset address

of the data specified by the Src.

LEA AX, NUMB

❖ AX ← operand offset address MUMB


LEA

Example:

LEA BX, [DI]

MOV BX, [DI]

; loads offset address

specified by [DI] (contents

of DI) into BX register

; loads the data stored at

the memory location

addressed by [DI] into BX

register

MOV BX, DI

= LEA BX, [DI]


LEA

MOV BX, DI performs in less time and is often

preferred to LEA BX, [DI]

Example:

LEA SI, [BX+DI]

If BX = 1000H, DI = 2000

Solution:

SI=BX+DI

=1000+2000=3000H (16-bit offset

address)


LEA

The sum generated by this instruction

LEA SI, [BX+DI]

is a modulo-64K sum drops any carry out of the

16-bit result

Example:

LEA SI, [BX+DI]

If BX = 1000H, DI = FF00H, SI = 0F00H

Solution:

SI=BX+DI

=1000+FF00=0F00 H instead of 10F00H

❖ LDS Des, Src❖ It loads 32-bit pointer from memory source to

destination register and DS.

❖ The offset is placed in the destination register

and the segment is placed in DS.

❖ To use this instruction the word at the lower

memory address must contain the offset and the

word at the higher address must contain the

segment.


LDS

❖ LDS Des, Src❖ Example:

LDS BX, [DI]

❖ If DS= 1000H, DI = 1000H

❖ The LDS BX, [DI] instruction loads register BX

from addresses 11000H and 11001H and register

DS from locations 11002H and 11003H. This

instruction is shown at the point just before DS

changes to 3000H and BX changes to 127AH.


LDS


LDS


LES

❖ LES Des, Src❖ It loads 32-bit pointer from memory source to

destination register and ES.

❖ The offset is placed in the destination register

and the segment is placed in ES.

❖ To use this instruction the word at the lower

memory address must contain the offset and the

word at the higher address must contain the

segment.

❖ This instruction is very similar to LDS except

that it initializes ES instead of DS.

❖ LES Des, Src❖ Example:

LES BX, [DI]

❖ If ES= 1000H, DI = 1000H

❖ The LES BX, [DI] instruction loads register BX

from addresses 11000H and 11001H and register

ES from locations 11002H and 11003H. This

instruction is shown at the point just before ES

changes to 3000H and BX changes to 127AH.


LES


LES

❖ LAHF:

❖ It transfer the lower byte of flag register to AH.AH ← FLAG (Lower 8-bit)

❖ SAHF:

❖ It transfer the contents of AH to lower byte of

flag register.FLAG (Lower 8-bit) ← AH

❖ PUSHF:

❖ Pushes flag register to top of stack.

❖ POPF:

❖Prof. FPayeoz Fp. Ms. El-tSohusye stack top to flag register.


LAHF, SAHF, PUSHF, POPF

XCHG Des, Src❖ This instruction exchanges Src with Des.

❖ It Exchanges contents of a register with any other

register or memory location.

❖ It can not exchange segment registers.

❖ It can not exchange two memory locations directly.

❖ Use any addressing mode except immediate.

❖ Example:

XCHG DX, AX

DX= 3000H, AX = 1000H

❖ After Execution this Instruction

DX= 1000H, AX = 3000H


XCHG

Example:

XCHG DX, AX

XCHG AL, CL

XCHG CX, BP

XCHG DX, SI

XCHG AL, [DI]


XCHG

XLAT❖ This instruction Converts the contents of the AL

register into a number stored in a memory table.

❖ It performs the direct table lookup technique often

used to convert one code to another.

❖ An XLAT instruction first adds the contents of AL to

BX to form a memory address within the data segment.

❖ It copies the contents of this address into AL.

❖ It is only instruction that adds an 8-bit to a 16-bit

number

❖ Example:

AL ← DS:[BX + AL]


XLAT (Translate)


XLAT (Translate)

The operation of the XLAT instruction at the point just before

6DH Pirosf. Flaoyeaz Fd. Me.dEl-Sionusyto AL.

❖ IN Accumulator, Port Address❖ This instruction transfers the operand from specified

port to accumulator register.

IN AX, 0028 H❖ An IN instruction transfers data from an external I/O

device into AL or AX

❖ OUT Port Address, Accumulator❖ This instruction transfers the operand from accumulator

to specified port.

OUT 0028 H, AX❖ An OUT transfers data from AL or AX to an external

I/O device.


IN and OUT

IN & OUT instructions perform I/O operations.

Contents of AL or AX are transferred only

between I/O device and microprocessor.

Two forms of I/O device (port) addressing:

Fixed-port addressing allows data transfer

between AL, or AX using an 8-bit I/O port

address.

Port number follows the instruction’s opcode.

IN AX, 0028 H

OUT 0028 H, AX


IN and OUT

Variable-port addressing allows data transfers

between AL or AX and a 16-bit port address.

The I/O port number is stored in register DX,

which can be changed (varied) during the

execution of a program.

MOV DX, 0028H

IN AX, DX

OUT DX, AX


IN and OUT


IN and OUT

The signals found in the microprocessor-based system for an OUT

19H, AX instruction.


IN and OUT

data movement instructions in microprocessor 8086/8088 · the operand can be a constant, memory...

Documents