FED cycle

• 1 


  The PC contains the address of the next instruction to be fetched
• 2


  The address contained in the PC is copied to the MAR via the address bus
• 3 


  the instruction is then copied from the memory location contained in the MAR and is placed in the MDR
• 4 


  the entire instruction is then copied from the MDR and placed in the CIR
• 5


  the value in the PC is then incremented so that it points to the next instruction to be fetched
• 6


  the address part of the instruction, if any, is placed in the MAR
• 7


  the instruction is finally decoded and is then executed
• MAR

  memory address register
• MDR

  memory data register
• CIR

  current instruction register
• PC

  program counter