INSTRUCTION CYCLE

Two phases :

1. Fetch
2. Execute

FETCH PHASE:
1. Program Counter (PC) holds address of next instruction to fetch
2.  Processor fetches instruction from memory location pointed to by PC
3. Instruction loaded into Instruction Register (IR)
4. Increment PC (but PC may be changed later…)

EXECUTE PHASE:
1. Processor decodes instruction and set-up circuits to
perform required actions
2.  Actual execution of operation:
Processor-memory
data transfer between CPU and main memory
3. Processor-I/O
data transfer between CPU and I/O module
4. Data processing
Some arithmetic or logical operation on data
5. Control
Alteration of sequence of operations e.g. jump
6. Combination of above

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