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Ethernet 1000BASE-X PCS/PMA or SGMII v9.1 www.xilinx.com 155
UG155 March 24, 2008
Overview of Operation
R
SGMII Standard
Figure 10-2 illustrates the operation of SGMII Auto-Negotiation. Additional information
about SGMII Standard Auto-Negotiation is provided in the following sections.
The SGMII capable PHY has two distinctive sides to Auto-Negotiation.
• The PHY performs Auto-Negotiation with its link partner using the relevant Auto-
Negotiation standard for the chosen medium (BASE-T Auto-Negotiation is illustrated
in Figure 10-2, using a twisted copper pair as its medium). This resolves the
operational speed and duplex mode with the link partner.
• The PHY then passes the results of the Auto-Negotiation process with the link partner
to the Ethernet 1000BASE-X PCS/PMA or SGMII core (in SGMII mode), by leveraging
the 1000BASE-X Auto-Negotiation specification described in “1000BASE-X Auto-
Negotiation Overview,” page 153. This transfers the results of the Link Partner Auto-
Negotiation across the SGMII and is the only Auto-Negotiation observed by the core.
This SGMII Auto-Negotiation function, summarized previously, leverages the 1000BASE-
X PCS/PMA Auto-Negotiation function but contains two differences.
• The duration of the Link Timer of the SGMII Auto-Negotiation is shrunk from 10 ms
to 1.6 ms so that the entire Auto-Negotiation cycle is much faster. See “Setting the
Configurable Link Timer,” page 156.
• The information exchanged is different and now contains speed resolution in addition
to duplex mode. See “MDIO Register 5: SGMII Auto-Negotiation Link Partner
Ability,” page 140.
There are no other differences and dealing with the results of Auto-Negotiation can be
handled as described previously in “1000BASE-X Auto-Negotiation Overview.”
Figure 10-2: SGMII Auto-Negotiation
Ethernet 1000BASE-X
PCS/PMA or SGMII
Core
Virtex-II Pro Device
Ethernet
Media
Access
Controller
PowerPC
MDIO
CoreConnect
an_interrupt
Auto-Neg Adv
(Reg 4)
Link Partner Ability
Base (Reg5)
SGMII capable
BASE-T PHY
Auto-Neg Adv
(Reg 4)
Link Partner Ability
Base (Reg5)
SGMII
link
Auto-Neg Adv
(Reg 4)
Link Partner Ability
Base (Reg5)
SGMII side
BASE-T side
Medium
(Twisted
Copper
Pair)
Link Partner
Auto-Neg Adv
(Reg 4)
Link Partner Ability
Base (Reg5)