Fetch-Execute-Decode Cycle

Question 1

Describe the stages of the Fetch part?

Answer 1

Fetch:
Program counter (PC) points to next instruction to be fetched.
2. Contents of (PC) copied into memory address register (MAR).
3. The instruction in (MAR) is transferred via the data bus to the memory buffer register (MBR).
4. The contents of the (MBR) are copied to instruction register (CIR) and the program counter (PC) is updated to address next instruction.

Question 2

Describe the stages of the Decode part?

Answer 2

Decode:
The instruction in the (CIR) is decoded.

Question 3

Describe the stages of the Execute part?

Answer 3

Execute:
1. The decoded instruction is executed.
2. The process is repeated.