FDE CYCLE

Question 1

Fetch

Answer 1

• PC is copied to MAR
• fetch signals are sent across the control bus, contents of mar across the address bus
• contents of the memory location stored in MAR are then sent across the data bus and stored in CIR
• PC’s value incremented by 1

Question 2

Decode

Answer 2

• contents of CIR are sent to the control unit

- Control unit then decodes the instruction

Question 3

Execute

Answer 3

-If the instruction carries a calculation then the contents of the MDR and ACC are sent to the ALU and the result is sent back to the ACC