Controller has

• Control register: GoR, GoW, IER, IEW
• Status register: RdyR, RdyW
• Read register
• Write register

      GoR  Go read  (start a read op)
      GoW  Go write (start a write op)
      IER  Enable read-completion interrupt
      IEW  Enable write-completion interrupt
      RdyR Ready to read  
      RdyW Ready to write