Data Sheet

Inline Functions—Ethernet Controller I210
291
• VLAN ID - the 12-bit tag indicating the VLAN group of the packet.
• Canonical Form Indication (CFI) - Set to zero for Ethernet packets.
• PRI - indicates the priority of the packet.
Note: The VLAN tag is sent in network order (also called big endian).
7.2.2.2 Advanced Transmit Context Descriptor
7.2.2.2.1 IPLEN (9)
IP header length. If an offload is requested, IPLEN must be greater than or equal to 20 and less than or
equal to 511.
7.2.2.2.2 MACLEN (7)
This field indicates the length of the MAC header. When an offload is requested (either TSE or IXSM or
TXSM is set), MACLEN must be larger than or equal to 14 and less than or equal to 127. This field
should include only the part of the L2 header supplied by the software device driver and not the parts
added by hardware. Table 7-30 lists the value of MACLEN in the different cases.
VLAN (16) - 802.1Q VLAN tag to be inserted in the packet during transmission. This VLAN tag is
inserted and needed only when a packet using this context has its DCMD.VLE bit set. This field should
include the entire 16-bit VLAN field including the CFI and Priority fields as listed in Table 7-28.
Note: The VLAN tag is sent in network order.
Table 7-29. Transmit Context Descriptor (TDESC) Layout - (Type = 0010b)
63 57 56 32 31 16 15 9 8 0
0 Reserved LaunchTime VLAN MACLEN IPLEN
63 48 47 40 39 38 36 35 30 29 28 24 23 20 19 9 8 0
8 MSS L4LEN RSV
1
IDX Reserved DEXT RSV
1
1. RSV - Reserved
DTYP TUCMD Reserved
Table 7-30. MACLEN Values
SNAP Regular VLAN External VLAN MACLEN
No By hardware or no VLAN No 14
No By hardware or no VLAN Yes 18
No By software No 18
No By software Yes 22
Yes By hardware or no VLAN No 22
Yes By hardware or no VLAN Yes 26
Yes By software No 26
Yes By software Yes 30