What are the steps of the fetch operation
1.The Program Counter has been pre-loaded with the starting address of the first instruction within the program
2. the program counter value is copied into the Memory Address Register
3.Once the MAR is loaded, the Control Unit loads the address on to the address bus and also sends a signal to main memory to read the instruction containted at that address.
4. Now the instruction is passed across the data bus and copied into the Memory Data Register.
5.Then the instruction in the MDR is copied into the Instruction Register so that it is ready to use during the next stage (decode)
6. The program counter is now incremented by one location, so that it is ready to begin the next fetch cycle.
What is step for the decode operation
- the control unit reads the Instruction Register and makes sure that it is an instruction that the CPU can carry out
What is the step for the execute operation
It carries out the instruction that has been decoded.
