Microprocessor Tutorial

8085 Microprocessor

8086 Microprocessor

Difference between

Microprocessor vs Microcontroller

The way in whic operands are specified in an assembly language instruction is called its addressing mode.

Following are the addressing modes in 8086:

  1. Register Addressing
  2. Immediate Addressing
  3. Direct Addressing
  4. Register Indirect Addressing
  5. Register Relative Addressing
  6. Based Indexed mode
  7. Relative Base Addressing Mode

Register Addressing

In this mode, both source and destination are registers.

MOV AL, AH
MOV SI, BX

Warning! Data types should match, either both (source and destination) are bytes or words.

Immediate Addressing

In this mode, data is in instruction itself.

MOV AL, 59H ;59H will be copied to AL.
MOV AX, 2569H


Direct Addressing

In this mode, either the source or the destination will be a memory address.

MOV [3458H], AL      ;move the byte to location 3458H
MOV AX, [2569H]


Register Indirect Addressing

In this mode, the address of the data is in a register.

MOV [SI], AL      ;move the content of AL to location pointed by SI
MOV AL, [BX]


Register Relative Addressing

In this mode, a displacement is added to get an effective address.

MOV CL, 10[BX]
move the content of the address specified by adding the content of BX and 10.

It can be written in different forms

MOV CL, [BX+10]
MOV CL, [BX]+10
MOV CL, [BX][10]


Based Indexed Mode

In this mode, an index register and a base register together carry the effective address.

MOV AL, [BX][SI]
move the content of the address pointed by [BX] and [SI] into AL


Relative Based Indexed Mode

In this mode, an index register, a base register and a displacement together carry the effective address.

MOV DL, 5[BX][DI]

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