SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
VLAN tagged packets are packets that contain a VLAN header specifying the VLAN the packet belongs to (VID), the packet priority (PRI), and the drop eligibility indicator (CFI). According to the CPSW_ALE_UVLAN_UNTAG[1-0] UVLAN_FORCE_UNTAGGED_EGRESS bit in the packet header, VLAN tagged packets may exit the switch with their VLAN priority replaced or they may have their VLAN header completely removed. The two cases are discussed below.
VLAN tagged input packets are output with the packet priority replaced with the header packet priority when the transmit packet header CPSW_ALE_UVLAN_UNTAG[1-0] UVLAN_FORCE_UNTAGGED_EGRESS bit is deasserted.
VLAN tagged input packets have the 4-byte packet VLAN information removed when the transmit packet header CPSW_ALE_UVLAN_UNTAG[1-0] UVLAN_FORCE_UNTAGGED_EGRESS bit is asserted. The VLAN_LTYPE_SEL length/type is removed as is the two byte packet VLAN. Input 64-67 byte VLAN tagged packets go out with the VLAN removed and padded to 64-bytes. The input CRC bytes are used as the pad data. Input 64-byte VLAN tagged packets use all four input CRC bytes as pad, input 65-byte priority tagged packets use three of the input CRC bytes as pad, and so on. The output CRC is replaced with a generated CRC when the VLAN is removed.