Datasheet

500
32117D–AVR-01/12
AT32UC3C
24.5.14 VLAN Support
An Ethernet encoded 802.1Q VLAN tag looks like this:
The VLAN tag is inserted at the 13
th
byte of the frame, adding an extra four bytes to the frame. If
the VID (VLAN identifier) is null (0x000), this indicates a priority-tagged frame. The MAC can
support frame lengths up to 1536 bytes, 18 bytes more than the original Ethernet maximum
frame length of 1518 bytes. This is achieved by setting bit 8 in the network configuration register.
The following bits in the receive buffer descriptor status word give information about VLAN
tagged frames:
• Bit 21 set if receive frame is VLAN tagged (i.e. type id of 0x8100)
• Bit 20 set if receive frame is priority tagged (i.e. type id of 0x8100 and null VID). (If bit 20 is
set bit 21 is set also.)
• Bit 19, 18 and 17 set to priority if bit 21 is set
• Bit 16 set to CFI if bit 21 is set
24.5.15 Wake-on LAN Support
The receive module supports wake-on LAN by detecting the following events on incoming
receive frames:
• Magic packet
• ARP request to the device IP address
• Specific address 1 filter match
• Multicast hash filter match
If one of these events occurs wake-on LAN detection is indicated by asserting WOL output pin
for 64 RX_CLK cycles. These events can be individually enabled by bits MAG, ARP, SA1 & MTI
in wake-on LAN register (WOL). Also, for wake-on LAN detection to occur, receive enable must
be set in the network control register (NCR), however a receive buffer does not have to be
available.
WOL assertion due to ARP request, specific address 1 or multicast filter events will occur even if
the frame is errored. For magic packet event, the frame must be correctly formed and error free.
A magic packet event is detected if all of the following are true:
• magic packet events are enabled by WOL.MAG bit
• the frame’s destination address matches specific address 1
• the frame is correctly formed with no errors
• the frame contains at least 6 bytes of 0xFF for synchronization
• there are 16 repetitions of the contents of specific address 1 register immediately following
the synchronization
An ARP packet event is detected if all of the following are true:
• ARP request are enabled by WOL.ARP bit
• broadcasts are allowed by NCFG.CAF
Table 24-4. 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