FDE Cycle

• FETCH

  • Copy memory address from the Program Counter to the MAR
  • Copy the instruction stored in the MAR address to the MDR
  • Increment the Program Counter
• DECODE

  • The instruction in the MAR is decoded by the CU
  • The CU may then prepare for the next step, for example by loading values into the MAR or MDR.
• EXECUTE

  • The instruction is performed
  • Examples include loading or writing data to memory, doing a calculation or halting the program.