EP80579 Datasheet, PDF (1398/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
The Flow Control Type Register (FCT) contains a 16 bit field which is compared against
the flow control packet’s type field to determine if it is a valid flow control packet: XON
or XOFF. 802.3x reserves this as 0x8808. This value must be loaded into the FCT.
The final check for a valid PAUSE frame is the MAC Control Opcode. At this time only
the PAUSE control frame opcode is defined. It has a value of 0x0001.
Frame based flow control differentiates XOFF from XON based on the value of the
PAUSE timer field. Non-zero values constitute XOFF frames while a value of zero
constitutes an XON frame. Values in the timer field are in units of slot time. A “slot
time” is hard wired to 64 byte times, or 512ns.
Note:
An XON frame signals the cancellation of the “pause” initiated by an XOFF frame.
“Pause for zero slot times.”
Figure 37-47.802.3x MAC Control Frame Format
1 Byte
S
Up to 6 Bytes Preamble...
1 Byte
6 Bytes
6 Bytes
SFD
Destination
Address
Source
Address
2 Bytes
Type/Length
2 Bytes
(min_FrameSize -160)/8
Bytes
MAC Control
Opcode
MAC Control
Parameters
Note:
4 Bytes
FCS
1 Byte
T
Where “S” is the Start-of-Packet delimiter and “T” is the first part of the End-of-Packet
delimiters for 802.3z encapsulation.
The receiver is enabled to receive flow control frames via the Device Control Register
(CTRL.RFCE).
Flow control capability must be negotiated between link partners via the Auto-
Negotiation process. The Auto-Negotiation process may modify the value of these bits
based on the resolved capability between the local device and the link partner.
Once the receiver has validated the reception of an XOFF, or PAUSE frame, the device
will:
• Increment the appropriate statistics register(s)
• Set the STATUS.TXOFF bit
• Initialize the pause timer based on the packet's PAUSE timer field
Intel^® EP80579 Integrated Processor Product Line Datasheet
1398
August 2009
Order Number: 320066-003US