Every instruction of a program has to operate on a data.
The method of specifying the data to be operated by the instruction is called Addressing.
The 8085 has the following 5 different types of addressing.
1. Immediate Addressing
2. Direct Addressing
3. Register Addressing
4. Register Indirect Addressing
5. Implied Addressing
1. Immediate Addressing:
In immediate addressing mode, the data is specified in the instruction itself. The data will be a part of the program instruction.
EX. MVI B, 3EH - Move the data 3EH given in the instruction to B register; LXI SP, 2700H.
2. Direct Addressing:
In direct addressing mode, the address of the data is specified in the instruction. The data will be in memory. In this addressing mode, the program instructions and data can be stored in different memory.
EX. LDA 1050H - Load the data available in memory location 1050H in to accumulator; SHLD 3000H
3. Register Addressing:
In register addressing mode, the instruction specifies the name of the register in which the data is available.
EX. MOV A, B - Move the content of B register to A register; SPHL; ADD C.
4. Register Indirect Addressing:
In register indirect addressing mode, the instruction specifies the name of the register in which the address of the data is available. Here the data will be in memory and the address will be in the register pair.
EX. MOV A, M - The memory data addressed by H L pair is moved to A register. LDAX B.
5. Implied Addressing:
In implied addressing mode, the instruction itself specifies the data to be operated.
EX. CMA - Complement the content of accumulator; RAL