COMP2 - Fetch-Execute

Question 1

Fetch - MAR <- PC

Answer 1

PC (address of next instruction) copied to MAR.

Question 2

Fetch - PC <- Memory

Answer 2

Instruction held at MAR copied to MBR.

Contents of PC incremented by 1 to prepare for next instruction.

Question 3

Fetch - CIR <- MBR

Answer 3

Contents of MBR copied to CIR.

Frees up space in MBR for executing.

Question 4

Decode - CIR

Answer 4

Instruction in CIR decoded.

Question 5

Execute - CIR

Answer 5

Instruction in CIR executed.

Result stored in accumulator.