Learning notes of Microcomputer Principles - common addressing methods

Common addressing methods

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1. Immediate addressing

The simplest way to address , Pass the immediate number directly to the destination operand .

MOV		AX,9099H		; Send the immediate number to AX

2. Register addressing ( Register direct addressing )

The operand is stored in the corresponding register . Short instruction code , There is no need to fetch operands from memory , Fast execution

MOV 	EDX,EBX
INC		CL	
MOV		DS,AX

3. Direct addressing （ Memory direct addressing ）

Operands are stored in memory , But the effective address is given directly by the instruction .EA It is stored in the memory code segment together with the operation code

MOV	AX,BUFFER		; Address BUFFER The operands in two consecutive byte addresses are sent to AX,BUFFER： The symbolic address of the storage unit in the memory .
// hypothesis BUFFER The offset address is 3000H,(DS)=5000H
MOV AX,DS:[3000H]	; The physical address 53000H The content in is sent to AL,53001H Send AH
 Equivalent to ：
MOV	AX,[3000H];
 In case of other segment registers , You need to add a transcendental prefix .
MOV AX,ES:[3000H];

4. Register indirection

Use the register to save the address of the storage unit , All storage units can be accessed through indirect addressing . namely Operands are stored in memory , But it's EA Stored in a register , From EA Read address , Then go to the corresponding address unit to find the corresponding content .
$$EA=[Sendsavedevice]$$

#16 Bit addressing , The offset address is stored in SI,DI,BP and BX
#1. With SI、DI、BX Indirect addressing , The default operand is DS paragraph 
	MOV AX,[DI]
#2. With BP Indirect addressing , The default operand is SS（stack segment） paragraph 
	MOV DX,[BP]
# If the operand is in another segment , You need to prefix the instruction operand with a segment override .

5. Base addressing

$$EA=[The\; basesiteSendsavedevice]+positionmoveThe\; amount$$

16 Bit addressing defaults to ：BX With DS As a segment register ;BP With SS As a segment register

MOV AX,[BP+24]		; Equivalent to  MOV AX,24[BP]

It is applicable to the retrieval of array elements of one-dimensional array

6. Addressing

$$EA=[The\; basesiteSendsavedevice]+positionmoveThe\; amount$$

16 Bit addressing defaults to ： only SI、DI As an index register , And the default is DS As a segment register

MOV AX,BUFFER[DI]		;BUFFER Is the offset equivalent to  MOV AX,[DI+BUFFER]

It is applicable to the retrieval of array elements of one-dimensional array

7. Proportional addressing

$$EA=[changesiteSendsavedevice]\times ThanexamplebecauseSon+positionmoveThe\; amount$$

MOV AX,TABLE[EBP*4]

Only applicable to 32 Bit addressing .

8. Base plus index register addressing

$$EA=[The\; basesiteSendsavedevice]+[changesiteSendsavedevice]$$

It is generally stipulated that the base register determines which segment register is used as the base pointer .

MOV AX,[BP][SI]		; from SI The decision defaults to DS As a segment base register 

It is often used for two-dimensional array retrieval and double loop

9. Base address plus proportional index addressing

$$EA=[changesiteSendsavedevice]\times ThanexamplebecauseSon+[The\; basesiteSendsavedevice]$$

Only 32 A situation .

10. Base address with displacement plus indexed addressing

$$EA=[changesiteSendsavedevice]+[The\; basesiteSendsavedevice]+positionmoveThe\; amount$$

MOV AX,[BX+DI+MASK]

This addressing operation is mainly used for two-dimensional array operations , The displacement is the starting address of the array .

11. Base address with displacement plus proportional index addressing

$$EA=[changesiteSendsavedevice]\times ThanexamplebecauseSon+[The\; basesiteSendsavedevice]+positionmoveThe\; amount$$

$

MOV AX,[BX+DI+MASK]

This addressing operation is mainly used for two-dimensional array operations , The displacement is the starting address of the array .

11. Base address with displacement plus proportional index addressing

$$EA=[changesiteSendsavedevice]\times ThanexamplebecauseSon+[The\; basesiteSendsavedevice]+positionmoveThe\; amount$$