Fetch, Decode and Execute Cycle

Question 1

Fetch:

Answer 1

• Programme counter is checked as it holds the address of the next instruction to be executed in memory.
• Address is used by the MAR in order to fetch the instruction needed from Main Memory (RAM) and bring it into the MDR.
• The Address in the PC is incremented to point to the next instruction.

Question 2

Decode:

Answer 2

• ## Now that the instruction is in the CPU, the CU decodes the instruction to see what has to be done.

Question 3

Execute:

Answer 3

• Now that the CPU knows what to do the instruction can be executed
• This generally depends on the nature of the instructions.