14.5.2.1. Instruction Fetch Stages

Try these first

1. 1.

   Define the term 'Program Counter'.

   Hint

   What does the PC hold?

2. 2.

   What is the difference between immediate and direct addressing modes?

   Hint

   Think about where the operand is located.

3. 3.

   What is the role of the Program Counter in instruction fetching?

   Hint

   Think about what keeps track of instruction order.

4. 4.

   In which addressing mode is the operand included directly in the instruction?

   • Immediate
   • Direct
   • Indirect

   Hint

   What means that the operand is 'immediate'?

5. 5.

   Given an instruction fetch sequence involving both direct and indirect addressing modes, detail what could happen if a memory address is incorrect.

   Hint

   Think about what happens in a real-life scenario when you try to find something that isn't there.

6. 6.

   Design an instruction sequence that effectively combines immediate and direct addressing modes to compute a simple arithmetic operation. Show how control signals would differ.

   Hint

   Visualize how the computer might prioritize fetching from memory vs. using an immediate value.