The X5IO IOB features can be accessed through traditional input, output, and bidirectional buffer primitives, as well as through the XCVR_X2 UNISIM as part of the X5IO PHY. X5IO PHY Resources focuses on the serializer/deserializer functions, while this chapter focuses on the IOB logic for both low-speed (direct to fabric) and high-speed use cases (using the PHY).