The following figure shows the MDIO ports of the core connected to the MDIO of an external STA
entity. In this situation, mdio_i, mdio_o, and
mdio_t must be connected to a 3-state buffer to create a
bidirectional wire, mdio. This 3-state buffer can either be external to
the FPGA or internally integrated by using an IOB IOBUF component with an appropriate
SelectIO™ interface standard suitable for the external PHY.