The following figure shows the MDIO ports of
the QSGMII core connected to the MDIO of an external STA entity. In
this situation, mdio_in_chx, mdio_out_chx, and mdio_tri_chx must be
connected to a 3-state buffer to create a bidirectional wire, mdio_chx.
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.
Figure 1. Creating an External MDIO Interface
