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2. Fetch

Step 1

The Program Counter copies the address of the next instruction it contains into the Memory Address Register (MAR).

Step 2

The Memory Address Register places the address to be used on to the 'Address Bus'

Step 3

The Memory Address Register triggers a 'read' signal that causes main memory (RAM) to place the instruction being asked for on to the 'Data Bus'

Step 4

The instruction on the data bus is loaded into the Memory Data Register (also called Memory Buffer Register)

Step 5

The Memory Data register copies the instruction into the 'Instruction Register'

The Fetch stage is now complete