6.4.8 VLAN Support
The following table describes an Ethernet encoded 802.1Q VLAN tag.
| TPID (Tag Protocol Identifier) 16 bits | TCI (Tag Control Information) 16 bits |
| 0x8100 | First 3 bits priority, then CFI bit, last 12 bits VID |
The VLAN tag is inserted at the 13th byte of the frame adding an extra four bytes to the frame. To support these extra four bytes, the MAC can accept frame lengths up to 1536 bytes by setting the 1536 Maximum Frame Size (MAXFS) bit in the Network Configuration register.
The MAC can be configured to reject all frames except VLAN tagged frames by setting the discard Non-VLAN Frames (DNVLAN) bit in the Network Configuration register.