Explain any three Addressing Modes of 8085 with examples.
Direct addressing mode :
(a) In direct addressing, the address appears after opcode of instruction in program memory.
(b) The address of operand is specified within the instruction.
(c) The instructions using direct addressing mode are three byte instructions. Byte 1 is opcode of instruction, Byte 2 is lower order address and Byte 3 is high order address.
(d) For e.g. LDA C060 H
i.e. This instruction loads accumulator with content of memory location C060 H.
(ii) Register addressing mode :
(a) In register addressing mode, the source operands are general purpose registers whose name is specified within the instruction.
(b) These instruction are single byte instructions.
(c) All actions occur within the CPU.
(d) For e.g. MOV A,B.
i.e. This instruction transfers the content of register B to accumulator without modifying content of B.
(iii) Immediate addressing mode :
(a) In Immediate addressing the data appears immediately after opcode of instruction in program memory.
(b) In these instructions the actual data is specified within the instruction.
(c) These operations are specified with either 2 or 3 byte instructions.
(d) For e.g. ADI 05H
i.e. this instruction adds immediate data 05 H to the content of accumulator. The result is stored in accumulator.