Fetch Decode Execute

Question 1

Name the steps of Fetch section

Answer 1

1) The PC points to the next instruction to be fetched. Contents of the PC are copied into the MAR. The address in MAR is sent down the address bus to RAM
2) The contents of the specified memory address are sent down the data bus to the MBR. The PC is incremented by 1 to point to the address of the next instruction.
3) The contents of the MBR are copied to the CIR

Question 2

Name the steps of Decode section

Answer 2

• The instruction is the CIR is decoded by splitting it into the opcode/operand.
• The opcode specifies the instruction and the opcode specifies either the immediate data to be used or a memory address.

Question 3

Name the steps of Execute section

Answer 3

The decoded instruction is executed.

Results are stored in the accumulator/memory