Immediate Addressing Mode in 8086 Microprocessor
Immediate addressing mode in 8086 microprocessor contains the instruction where the first operand may be a register or memory location and the second operand is an immediate value that represents the operand. In this article, we will explore the immediate addressing mode in detail along with the examples of immediate addressing mode. Also, we will discuss the advantages and disadvantages and applications of immediate addressing mode.
Table of Content
- Immediate Addressing Mode
- 8086 Microprocessor Instruction
- Operations
- Examples
- Advantages and Disadvantages
- Applications
What is Immediate Addressing Mode in 8086 Microprocessor?
The immediate addressing mode in the 8086 microprocessor is the addressing mode in which the value of the operand is given directly in the instruction itself. In other words, in the immediate addressing mode in the 8086 microprocessor, the operand is present in the source operand of the instruction. The immediate addressing mode is commonly used addressing mode for initializing the value to the registers then the operation is performed. Some instructions directly take the value from the source operand in the immediate addressing mode and perform operations on it. Also, the destination operand cannot have immediate data. The segment registers cannot be initialized using the immediate data it needs to register to be initialized.
8086 Microprocessor Instruction with Immediate Addressing Mode
Representation of 8086 microprocessor instruction with immediate addressing modes.
Opcode Destination Operand, Source Operand |
|||
---|---|---|---|
Opcode Register, Immediate Value |
Operations of Immediate Addressing Mode
We know that in immediate addressing mode the operand in present in the instruction only as an immediate value. So, to perform any operation on the operand we directly fetch the operand from the source address field of the instruction. Consider the instruction format given below.
Opcode |
Destination Address |
Source Address |
---|---|---|
↓ |
↓ |
↓ |
Operation Decode |
Destination address |
Operand (immediate value) |
Consider an example instruction.
MOV AL, 20H
Operations performed while executing the above instruction is given below.
AL ← 20H
Examples of 8086 Instruction with Immediate Addressing Mode
Some examples of immediate addressing modes in 8086 microprocessors are given below.
Instructions of 8086 microprocessor (immediate addressing used) |
Description |
---|---|
MOV AX, 0103H |
This instruction has an immediate value 0103H as its source operand and initializes the value of register AX with the immediate data. |
MOV DH, 50H |
This instruction has an immediate value 50H as its source operand and initializes the value of register DH with the immediate data. |
ADD BX, 1025H |
This instruction has an immediate value 1025H as its source operand and adds the immediate data with the content of register BX. |
MUL AH, 10H |
This instruction has an immediate value 10H as its source operand and multiplies the immediate data with the content of register AH. |
Advantages and Disadvantages of Immediate Addressing Mode
Some of the advantages and disadvantages of immediate addressing modes are listed below.
Advantages of Immediate Addressing Mode in 8086 Microprocessor
Some of the advantages of immediate addressing modes are listed below.
- Operand is specified in the instruction itself, so no computation and calculation are required to fetch the operand.
- The effective address not required for the operand as it is present within the instruction.
- The additional fetches for the operand are not required hence simplifying the instruction execution cycle.
Disadvantages of Immediate Addressing Mode in 8086 Microprocessor
Some of the disadvantages of immediate addressing modes are listed below.
- The size of the operand is limited according to the instruction format.
- The size of immediate value is constrained with the size of address field in the instruction.
- The first operand in the instruction cannot be an immediate value.
Applications of Immediate Addressing Mode
Some applications of immediate addressing modes are listed below.
- Immediate addressing mode can be used to initialize the registers.
- The immediate value in the immediate addressing mode can be directly used as operand.
Conclusion
From the above discussion we can conclude that the 8086 microprocessors have different addressing modes. In the immediate addressing mode of 8086 microprocessor the operand in which the operation is to be performed is present within the instruction. The operand is fetched from the address part of the instruction of 8086 microprocessor and the desired operation is performed on this operand.
Immediate Addressing Mode in 8086 Microprocessor – FAQs
What is Effective Address?
The address of the operand in which operation is to be performed is called as the effective address.
What is Addressing Mode?
The addressing modes defines the effective address of the operand or the target address in the branch instructions. The addressing modes gives the information about the operand in which the specified operation is to be performed.
What are the Different Addressing Modes in 8086 Microprocessor?
The different addressing modes in 8086 microprocessors.
- Immediate Mode
- Register Mode
- Direct Mode
- Register Indirect Mode
- Indexed Mode
- Relative Mode
- Based Indexed Mode