Abstract: A link control state machine controls a media access controller (MAC), a serial physical sublayer (serial PHY) and a media independent interface physical sublayer (MII PHY). In a first state of the link control state machine, an attempt is made to establish a link via the MII PHY. If successful, a second state is entered and the MAC performs data transfer using the MII PHY while the serial PHY is isolated from the MAC. In a third state, an attempt is made to establish a network link via a serial PHY. The MII PHY is isolated from the MAC and a test frame is sent using the serial PHY. The third state is entered from the first state when there is a link timeout on the MII PHY. In a fourth state, the MAC performs data transfer using the serial PHY. The fourth state is entered from the third state if the test frame was transmitted successfully.