EP80579 Datasheet, PDF (1394/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
In the case of a collision, the PHY detects the collision and asserts the COL signal to the
MAC. Transmission of the frame stops within four link clock times, and the GbE sends a
JAM sequence onto the link. After the end of a collided transmission, the GbE will back
off and attempt to retransmit per the standard CSMA/CD method. Note that the re-
transmissions are done from the data stored internally in the GbE transmit packet
buffer (no re-access to the data in host memory is necessary).
In the case of a successful transmission, the GbE is ready to transmit any other
frame(s) queued in the transmit FIFO, after the minimum inter-frame spacing (IFS) of
the link has elapsed.
During transmit, the PHY is expected to signal a carrier-sense (assert the CRS signal)
back to the MAC before one slot time has elapsed. The transmission will complete
successfully even if the PHY fails to indicate CRS within the slot time window. If this
situation occurs, the PHY may either be configured incorrectly or be in a link down
situation. Such an event will be counted in the statistic register space, refer to “TNCRS
– Transmit with No CRS Count Register” on page 1510.
MII mode half duplex reception occurs exactly as indicated in “Full Duplex” on
page 1393. Reception is signaled by the PHY by the assertion of the RX_DV signal
which indicates valid receive data on the RX_DATA lines to the MAC.
37.5.8.3
Physical Layer Auto-Negotiation & Link Setup Features
The method for configuring the link between two link partners is highly dependent on
the mode of operation as well as the functionality provided by the specific physical layer
device. For GMII/MII mode, the PCS and Auto-Negotiation functions are expected to be
maintained within the external PHY.
Configuration of the link may be accomplished by several methods ranging from
software's forcing link settings, to software-controlled negotiation, to auto-negotiation
initiated by the PHY. The following sections describe processes of bringing the link up
including configuration of the GbE and the transceiver, as well as the various methods
of determining duplex and speed configuration in order to configure the MAC.
When operating in a GMII/MII mode, the external PHY performs auto-negotiation per
802.3ab clause 40 and extensions to clause 28. Link resolution is obtained by software
from the PHY after the link has been established and programs the MAC with these
settings.
37.5.8.3.1
GMII/MII/Copper Link Configuration
When operating in GMII/MII mode, link configuration is generally determined by Auto-
Negotiation between the PHY and it’s link partner. The driver must poll the
configuration in cases after a successful link is established or the user desires to
manually configure the link. The following sections discuss the methods of link
configuration for copper PHY operation.
37.5.8.3.2
GMII/MII/Copper Auto-Negotiation (Speed, Duplex, Flow-Control)
When using a copper PHY, the PHY performs the Auto-Negotiation function. The actual
operational details of this operation are described in the IEEE P802.3ab draft standard,
and are not included here.
Auto-Negotiation provides a method for two link partners to exchange information in a
systematic manner in order to establish a link configuration providing the highest level
of functionality supported by both partners. Once configured, the link partners
exchange configuration information to resolve link settings such as:
• Speed (10/100/1000 Mbps)
Intel^® EP80579 Integrated Processor Product Line Datasheet
1394
August 2009
Order Number: 320066-003US