Saturday, August 10, 2013

Addressing Modes:-


          Each instruction requires certain data in which it has to operate. There are various technique to specify data for instruction. These technique are called addressing mode.
            The 8085 consists of 5 different addressing modes. They are:
1.     Direct Address Mode:     In this mode of addressing, the address of the operand is given in the instruction itself. E.g. STA 2000H, IN 02H.         
2.     Immediate Addressing Mode: In this addressing mode, the operand is specified within the instruction itself. E.g. MVI A, 20H and LXI H, 2500H.
3.     Register Addressing Mode:      The operands are in general purpose register. The op-code specifies the address of the registers in addition to the operation to be performed. E.g. MOV A, B and ADD B.
4.     Register Indirect Addressing Mode:  In this mode of addressing, the address of operand is specified by the register pair as a pointer of operand. E.g. LXI M, 2000H and MOV A, M.
5.     Implied Addressing Mode:        These are certain instruction which operate on the content of an accumulator, such instruction do not require the address of operand. E.g. CMA, RAR, HLT etc.

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