Which instruction is the example of immediate addressing mode ?

Explanation:

Immediate Addressing Mode in Assembly Language

Definition: Immediate addressing mode is a way of specifying the operand within the instruction itself. In this mode, the operand is given explicitly in the instruction, rather than being stored in a register or a memory location. This means that the value to be used in the operation is embedded directly in the machine code instruction.

Working Principle: When an instruction using immediate addressing mode is executed, the operand value is directly fetched from the instruction itself rather than from a memory address or a register. This makes the execution of such instructions faster as there is no need to access memory or registers to retrieve the operand value.

Advantages:

• Simplicity and speed, as the operand is directly available in the instruction.
• Reduces the need for additional memory accesses, making the instruction execution faster.
• Useful for defining constants and fixed values within the program.

Disadvantages:

• Limited operand size due to the instruction length constraints.
• Less flexibility as the operand value is hard-coded in the instruction and cannot be changed at runtime.

Applications: Immediate addressing mode is commonly used for initializing registers, defining constants, and performing operations where the operand value is known at the time of instruction writing.

Correct Option Analysis:

The correct option is:

Option 1: MOV A, #25H

This option exemplifies immediate addressing mode. The operand (25H) is given directly in the instruction. When executed, the value 25H is moved to the register A without the need for accessing any memory location or register other than the instruction itself.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: MOV A, R0

This option uses register addressing mode, where the operand is located in a register (R0). The instruction moves the content of register R0 to the register A. This is not an example of immediate addressing mode, as the operand is not given directly in the instruction.

Option 3: MOV R3, A

This option also uses register addressing mode. The content of register A is moved to register R3. Again, the operand is not provided directly in the instruction but is retrieved from another register, making it a register addressing mode.

Option 4: MOV R0, 40H

This option uses direct addressing mode, where the operand address (40H) is specified directly in the instruction. The content of the memory location 40H is moved to register R0. This is different from immediate addressing mode, as the operand value itself is not embedded in the instruction but is stored at a specific memory location.

Conclusion:

Understanding the different addressing modes is crucial for correctly identifying how operands are accessed and used in assembly language instructions. Immediate addressing mode, as explained, involves the operand being directly embedded in the instruction, resulting in faster execution due to the absence of additional memory or register accesses. This makes it particularly useful for operations requiring constant values. The correct option (MOV A, #25H) clearly demonstrates this mode by providing the operand value (25H) directly within the instruction.