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8085 Addressing Modes

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Addressing modes: The different methods which are used to select or address the operands are called addressing modes or the different modes or ways that a microprocessor uses to access data are called addressing modes.

There are five addressing modes:
  • Immediate addressing mode
  • Register addressing mode
  • Direct addressing mode
  • Indirect addressing mode
  • Implied addressing mode

Immediate addressing mode: 

  • In this addressing mode, 8-bit data or 16-bit data is specified in instruction itself.
  • These instructions can be either two byte or three byte instructions.
  • The instructions containing 'I' indicates immediate addressing mode.
Example: 
MVI C, 31H
LXI H, 3210H

Register addressing mode:

  • In this addressing mode, the source and destination operands are general purpose registers (B, C, D, E, H and L).
  • These instructions are one byte instructions.
Example: 
MOV A, B
PCHL

Direct addressing mode: 

  • In this addressing mode, the 16-bit address of the operand is given within the instruction itself.
  • These instructions are three byte instructions.
Example:
LDA 5600H
STA C200H

Indirect addressing mode:

  • In this addressing mode, the memory address where the operand is located is indicated by the contents of the register pair.
  • These instructions are one byte instructions.
Example:
MOV A, M
LDAX C

Implied addressing mode:

  • In this addressing mode, no operand is required.
  • It is also known as implicit addressing mode.
  • These instructions are one byte instructions.
Example:
RAL
CMA

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