YEAR 1 CO1 WEEK 5 FDE CYCLE

Question 1

Describe FETCH part of the cycle.

Answer 1

Value from PC loaded into MAR.
Fetch Signal sent down the control bus and this sends value in MAR down the address bus.
Contents of memory of specified location sent down data bus stored in MDR.
Copied to CIR.
PC then incremented.

Question 2

Describe DECODE part of cycle.

Answer 2

Contents of CIR sent to Control Unit.
It decodes the instruction.
If necessary also brings data for instruction to use and stores in appropriate registers.

Question 3

Describe EXECUTE part of cycle.

Answer 3

CU and/or ALU carries out the instruction stored in CIR and cycle begins again!