5 Questions
Explain the concept of Implied Addressing Mode and provide an example of an instruction that utilizes this mode.
Implied Addressing Mode is a mode in which the operands are implicitly specified by the definition of the instruction itself. An example of an instruction that utilizes this mode is 'Complement Accumulator' (CMA).
What is the key characteristic of Stack Addressing Mode and give an example of an instruction that employs this mode?
The key characteristic of Stack Addressing Mode is that the operand is contained at the top of the stack. An example of an instruction that employs this mode is 'ADD', where the instruction pops out two symbols from the top of the stack, performs addition, and pushes the result back to the top of the stack.
Describe the Immediate Addressing Mode and explain how the operand is specified in this mode.
Immediate Addressing Mode is a mode in which the operand is explicitly specified in the instruction. Instead of an address field, an operand field is present that contains the operand.
What is the purpose of Relative Addressing Mode and how does it work?
The purpose of Relative Addressing Mode is to specify an operand relative to the current program counter or instruction pointer. It works by using an offset from the current program counter to access the operand.
Differentiate between Register Direct Addressing Mode and Register Indirect Addressing Mode.
Register Direct Addressing Mode involves specifying the operand directly in a register, while Register Indirect Addressing Mode involves specifying the address of the operand in a register.
Study Notes
Addressing Modes
Implied Addressing Mode
- In this mode, the operand is implied by the instruction itself and is not explicitly specified.
- Example: The "Clear Carry Flag" (CLC) instruction, which clears the carry flag bit, implies that the operand is the carry flag itself.
Stack Addressing Mode
- This mode uses a stack-based memory organization, where the top of the stack is implicitly accessed.
- Example: The "Push" (PUSH) instruction, which pushes the accumulator value onto the stack.
Immediate Addressing Mode
- In this mode, the operand is specified directly as part of the instruction.
- The operand is an immediate value, which is a constant value embedded in the instruction.
- Example: The "Load Accumulator with Immediate" (LDA #nn) instruction, where #nn is the immediate value (e.g., LDA #$05 loads the value 5 into the accumulator).
Relative Addressing Mode
- This mode allows for conditional branching within a program.
- The operand specifies a relative offset from the current program counter (PC) value.
- The PC is updated by adding the relative offset to the current PC value.
Register Addressing Modes
- Register Direct Addressing Mode: The operand specifies a register that contains the desired value.
- Register Indirect Addressing Mode: The operand specifies a register that holds the memory address of the desired value.
- Example: The "Load Accumulator from Memory" (LDA $nn,X) instruction, where $nn is the memory address stored in the X register.
Test your knowledge of computer architecture with this quiz on addressing modes. Learn and identify nine different ways of specifying the location of an operand in an instruction, including implied, stack, immediate, direct, indirect, register direct, register indirect, relative, and indexed addressing modes.
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