The Fetch-Decode-Execute Cycle; including its effects on registers

Question 1

What happens during the fetch phase?

Answer 1

• Address from the PC is copied to the MAR
• Instruction held at that address is copied to MDR by the data bus
• Simultaneously, the contents of the PC are increased by 1
• The value held in the MDR is copied to the CIR

Question 2

What happens during the decode phase?

Answer 2

The contents of CIR are split into operand and opcode

Question 3

What happens during the execute phase?

Answer 3

The decoded instruction is executed

Question 4

A CPU may need to stop running the fetch-decode-execute cycle in order to handle an interrupt, when would it be handled?

Answer 4

After the execute phase, done after all other processes are executed/run