Addressing mode of 8085 microprocessor

To work with 8085 microprocessor, we should have clear idea on addressing mode of 8085 microprocessor. Addressing mode of 8085 microprocessor tells us by using the assembly language instruction that how can we process or address the data? Each instruction indicates an operation to be performed on certain data. There are various methods to specify the data for the instructions, known as ‘addressing modes’.

There are five addressing modes in 8085 microprocessor. These are:

  • Direct addressing
  • Register addressing
  • Register indirect addressing
  • Immediate addressing
  • Implicit addressing.

The examples for each type of addressing mode are given below:

Direct Addressing:

In this mode, as name suggest the operand is specified within the instruction itself directly after opcode.

Examples of Direct Addressing mode type are: LDA 4000H, STA 5513H, etc.

IN/OUT instructions (like IN PORT C, OUT PORT B, etc.) also falls under this category.

Register Addressing:

In this mode of addressing, the operand are in the general purpose registers. So after opcode here you find the general purpose registers.

  Examples are: MOV A, B ; ADD D, etc.

Register Indirect Addressing: 

These instructions utilise 1-byte. In this mode, instead of specifying a register, a register pair is specified to accommodate the 16-bit address of the operand. For register indirect addressing, HL register pair is specified to accommodate the 16-bit address of the operand.

Examples of this mode of addressing are MOV A, M; ADD M.

Immediate Addressing: The operand is specified in the instruction in this mode. Here, the operand address is not specified. That means specific data which have to process is on the followed by opcode.

Examples of Immediate Addressing mode are MVI A, 07; ADI 0F.

Implicit Addressing: In this mode of addressing, the operand is fully absent. Examples of Implicit Addressing are RAR, RAL, CMA, etc. mainly this type addressing used in machine controlling.

Hope the above discussion on addressing mode of 8085 microprocessor is clear your doubt.

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