There are six ways to find the address of the storage unit of operands.

1. Immediate addressing

The operands to be found are binary or decimal numbers, which appear in the instruction and are prefixed with “#”

MOVA,#20H

2. Register addressing

The operands are stored in the working registers R0 to R7, or in register B.

MOVA,R2

3. Direct addressing

Instruction gives the address of the operands directly.

MOVA,30H

MOV30H,DPH

4. Register indirect addressing

The contents of the register in the instruction are used as the address of the operands. The prefix “@” is used before the indirect addressing register in the instruction.

Analysis of the method of searching for the address of the storage unit of operands by single chip microcomputer

MOVR0,#30H

MOVA,@R0

MOVA,#20H

MOVR1,#40H

[email protected] ,A

5. Index addressing

Operands address = variable address + base address

Base address register dptr or PC

Index register @ a

This addressing method is often used to access program memory and look up tables.

MOVA,@A + DPTR

6. Relative addressing

Add the address offset given in the instruction and the address of the unit where the instruction is located (PC content) to get the address where the real effective operands are stored.

JC60H; Let (PC) = 2000h,

Then when C = 1,

Destination address of transfer = PC) + 2 + 60

Source; 21ic

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