Xilinx 1000BASE-X manual Sgmii Standard, Overview of Operation, Sgmii Auto-Negotiation

Overview of Operation

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SGMII Standard

Figure 10-2illustrates the operation of SGMII Auto-Negotiation. Additional information about SGMII Standard Auto-Negotiation is provided in the following sections.

Virtex-II Pro Device
	Ethernet 1000BASE-X
	PCS/PMA or SGMII
Ethernet	Core
	Auto-Neg Adv	SGMII
Media
Access	(Reg 4)	link
Controller	MDIO
	Link Partner Ability
	Base (Reg5)
	CoreConnect
PowerPC
	an_interrupt
	Figure 10-2:

SGMII capable

BASE-T PHY

SGMII side	BASE-T side
Auto-Neg Adv	Auto-Neg Adv
(Reg 4)	(Reg 4)
Link Partner Ability	Link Partner Ability
Base (Reg5)	Base (Reg5)

SGMII Auto-Negotiation

Medium (Twisted Copper Pair)

Link Partner

Auto-Neg Adv

(Reg 4)

Link Partner Ability

Base (Reg5)

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-XAuto-Negotiation Overview.”

Ethernet 1000BASE-X PCS/PMA or SGMII v9.1 www.xilinx.com 155

UG155 March 24, 2008