The KSZ9021 is a completely integrated triple speed (10Base-T/100Base-TX/1000Base-T) Ethernet Physical Layer Transceiver for transmission and reception of data over standard CAT-5 unshielded twisted pair (UTP) cable.
The KSZ9021Gxx provides the industry standard Gigabit Media Independent Interface/Media Independent Interface (GMII/MII) for connection to GMII/MII MACs in Gigabit Ethernet Processors and Switches for data transfer at 1000Mbps or 10/100Mbps speed. The KSZ9021Rxx provides the Reduced Gigabit Media Independent Interface (RGMII)