The LAN9312 is a full featured， 2 port 10/100 managed Ethernet switch designed for embedded applications where performance， flexibility， ease of integration and system cost control are required. The LAN9312 combines all the functions of a 10/100 switch system， including the switch fabric， packet buffers， buffer manager， media access controllers （MACs）， PHY transceivers， and host bus interface. The LAN9312 complies with the IEEE 802.3 （full/half-duplex 10BASE-T and 100BASE-TX） Ethernet protocol specification and 802.1D/802.1Q network management protocol specifications， enabling compatibility with industry standard Ethernet and Fast Ethernet applications. At the core of the LAN9312 is the high performance， high efficiency 3 port Ethernet switch fabric. The switch fabric contains a 3 port VLAN layer 2 switch engine that supports untagged， VLAN tagged， and priority tagged frames. The switch fabric provides an extensive feature set which includes spanning tree protocol support， multicast packet filtering and Quality of Service （QoS） packet prioritization by VLAN tag， destination address， port default value or DIFFSERV/TOS， allowing for a range of prioritization implementations. 32K of buffer RAM allows for the storage of multiple packets while forwarding operations are completed， and a 1K entry forwarding table provides ample room for MAC address forwarding tables. Each port is allocated a cluster of 4 dynamic QoS queues which allow each queue size to grow and shrink with traffic， effectively utilizing all available memory. This memory is managed dynamically via the buffer manager block within the switch fabric. All aspects of the switch fabric are managed via the switch fabric configuration and status registers， which are indirectly accessible via the memory mapped system control and status registers.