EP80579 Datasheet, PDF (1400/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
37.5.8.5.4 Software Initiated PAUSE Frame Transmission
The GbE has the added capability to transmit an XOFF frame via software. This is
accomplished by software using the Transmit Control Register (TCTL.SWXOFF). Once
this bit is set, hardware will initiate the transmission of a PAUSE frame in a manner
similar to that automatically generated by hardware.
TCTL.SWXOFF is self clearing after the PAUSE frame has been transmitted.
The state of the CTRL.TFCE bit or the negotiated flow control configuration does not
affect software generated PAUSE frame transmission.
Note:
Software sends an XON frame by programming a zero in the PAUSE timer field of the
FCTTV register. XOFF transmission is not supported in 802.3x for half duplex links.
Software should not initiate an XOFF or XON transmission if the device is configured for
half duplex operation.
37.5.9 802.1q VLAN Support
The GbE provides specific mechanisms to support 802.1q VLANs, namely:
• Optional adding (for transmits) and ping (for receives) of IEEE 802.1q VLAN tags.
• Optional ability to filter packets belonging to certain 802.1q VLANs.
The difference between an untagged 802.3 Ethernet packet and an 802.1q VLAN
tagged packet is minimal, as shown in Table 37-4.
Table 37-4. Untagged 802.3 Packet vs 802.1q VLAN tagged Packet
802.3 Packet
Number of
Octets
802.1q VLAN Packet
Number of
Octets
DA
6
DA
6
SA
6
SA
6
Type/Length
2
802.1q Tag
4
Data
46-1500
Type/Length
2
CRC
4
Data
46-1500
CRC^*
4
* _{The CRC for the 802.1q tagged frame is re-computed, so that it covers the entire tagged}
frame including the 802.1q tag header. Also, max frame size for an 802.1q VLAN packet is 1522
octets as opposed to 1518 octets for a normal 802.3z Ethernet packet.
37.5.9.0.1 802.1q Tagged Frames
For 802.1q, the Tag Header field consists of four octets comprised of the Tag Protocol
Identifier (TPID) and Tag Control Information (TCI); each taking 2 octets. The first 16
bits of the tag header makes up the TPID. It contains the “protocol type” which
identifies the packet as a valid 802.1q tagged packet.
The two octets making up the TCI contain three fields:
• User Priority (UP)
• Canonical Form Indicator (CFI), which should be “0” for transmits. For receives, the
device has the capability to filter out packets that have this bit set. Refer to
RCTL.CFIEN and RCTL.CFI described in Section 37.6.4.1, “RCTL – Receive Control
Register”.
• VLAN Identifier (VID)
Intel^® EP80579 Integrated Processor Product Line Datasheet
1400
August 2009
Order Number: 320066-003US