Data Sheet

Ethernet Controller I210 —Interconnects
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3.7.4 Auto-Negotiation and 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 (PHY or SerDes). In
SerDes/1000BASE-BX mode, the I210 provides the complete PCS and Auto-negotiation functionality as
defined in IEEE802.3 clause 36 and clause 37. In internal PHY mode, the PCS and IEEE802.3 clause 28
and clause 40 auto-negotiation functions are maintained within the PHY. In SGMII mode, the I210
supports the SGMII link auto-negotiation process, whereas the link auto-negotiation, as defined in
IEEE802.3 clause 28 and clause 40, is done by the external PHY. In 1000BASE-KX mode, the I210
supports only parallel detect of 1000BASE-KX signaling and does not support the full Auto-Negotiation
for Backplane Ethernet protocol as defined in IEEE802.3ap clause 73.
Configuring the link can be accomplished by several methods ranging from software forcing link
settings, software-controlled negotiation, MAC-controlled auto-negotiation, to auto-negotiation initiated
by a PHY. The following sections describe processes of bringing the link up including configuration of the
I210 and the transceiver, as well as the various methods of determining duplex and speed
configuration.
The process of determining link configuration differs slightly based on the specific link mode (internal
PHY, SerDes/1000BASE-BX, SGMII or 1000BASE-KX) being used.
When operating in a SerDes/1000BASE-BX mode, the PCS layer performs auto-negotiation per clause
37 of the 802.3z standard. The transceiver used in this mode does not participate in the auto-
negotiation process as all aspects of auto-negotiation are controlled by the I210.
When operating in internal PHY mode, the PHY performs auto-negotiation per 802.3ab clause 40 and
extensions to clause 28. Link resolution is obtained by the MAC from the PHY after the link has been
established. The MAC accomplishes this via the MDIO interface, via specific signals from the internal
PHY to the MAC, or by MAC auto-detection functions.
When operating in SGMII mode, the PCS layer performs SGMII auto-negotiation per the SGMII
specification. The external PHY is responsible for the Ethernet auto-negotiation process.
When operating in 1000BASE-KX mode the I210 performs parallel detect of 1000BASE-KX operation
but does not implement the full auto-negotiation for backplane Ethernet sequence as defined in
IEEE802.3ap clause 73.
3.7.4.1 SerDes/1000BASE-BX Link Configuration
When using SerDes/1000BASE-BX link mode, link mode configuration can be performed using the PCS
function in the I210. The hardware supports both hardware and software auto-negotiation methods for
determining the link configuration, as well as allowing for a manual configuration to force the link.
Hardware auto-negotiation is the preferred method.
3.7.4.1.1 Signal Detect Indication
When the CONNSW.ENRGSRC bit is set to 1b, the SRDS_SIG_DET pins can be connected to a Signal
Detect or loss-of-signal (LOS) output of the optical module that indicates when no laser light is being
received when the I210 is used in a 1000BASE-SX or -LX implementation (SerDes operation). No
standard polarity for the signal detect or loss-of-signal driven from different manufacturer optical
modules exists. The CTRL.ILOS bit provides the capability to invert the signal from different external
optical module vendors, and should be set when the external optical module provides a negative-true
loss-of-signal.