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LAN9303i Datasheet(PDF) 74 Page - SMSC Corporation |
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LAN9303i Datasheet(HTML) 74 Page - SMSC Corporation |
74 / 366 page Small Form Factor Three Port 10/100 Managed Ethernet Switch with Single MII/RMII/Turbo MII Datasheet Revision 1.3 (08-27-09) 74 SMSC LAN9303/LAN9303i DATASHEET 6.4.4 VLAN Support The Switch Engine supports 16 active VLANs out of a possible 4096. The VLAN table contains the 16 active VLAN entries, each consisting of the VID, the port membership, and un-tagging instructions. On ingress, if a packet has a VLAN tag containing a valid VID (not 000h or FFFh), the VID table is searched. If the VID is found, the VLAN is considered active and the membership and un-tag instruction is used. If the VID is not found, the VLAN is considered foreign and the membership result is NULL. A NULL membership will result in the packet being filtered if Enable Membership Checking is set. A NULL membership will also result in the packet being filtered if the destination address is not found in the ALR table (since the packet would have no destinations). On ingress, if a packet does not have a VLAN tag or if the VLAN tag contains VID with a value of 0 (priority tag), the packet is assigned a VLAN based on the Port Default VID (PVID) and Priority. The PVID is then used to access the above VLAN table. The usage of the PVID can be forced by setting the 802.1Q VLAN Disable bit, in effect creating port based VLANs. The VLAN membership of the packet is used for ingress and egress checking and for VLAN broadcast domain containment. The un-tag instructions are used at egress on ports defined as hybrid ports. Refer to Section 13.4.3.8, on page 280 through Section 13.4.3.11, on page 284 for detailed VLAN register descriptions. 6.4.5 Spanning Tree Support Hardware support for the Spanning Tree Protocol (STP) and the Rapid Spanning Tree Protocol (RSTP) includes a per port state register as well as the override bit in the MAC Address Table entries (Section 6.4.1.5, on page 68) and the host CPU port special tagging (Section 6.4.10, on page 80). The Switch Engine Port State Register (SWE_PORT_STATE) is used to place a port into one of the modes as shown in Table 6.2. Normally only Port 1 and Port 2 are placed into modes other than forwarding. Port 0, which is connected to the host CPU, should normally be left in forwarding mode. Figure 6.6 VLAN Table Entry Structure Table 6.2 Spanning Tree States Port State Hardware Action Software Action 11 - Disabled Received packets on the port are always discarded. Transmissions to the port are always blocked. Learning on the port is disabled. The host CPU may attempt to send packets to the port in this state, but they will not be transmitted. 17 16 15 14 13 12 VID 11 0 ... Un-tag MII Member MII Un-tag Port 1 Member Port 1 Un-tag Port 2 Member Port 2 |
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