Xilinx 1000BASE-X manual Auto-Negotiation

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Chapter 10: Auto-Negotiation

a link segment (the link partner) and to detect corresponding operational modes that the link partner advertises. Figure 10-1illustrates the operation of 1000BASE-X Auto- Negotiation.

The following describes typical operation when Auto-Negotiation is enabled.

1.Auto-Negotiation starts automatically when any of the following conditions are met.

♦Power-up/reset

♦Upon loss of synchronization

♦The link partner initiates Auto-Negotiation

♦An Auto-Negotiation Restart is requested (See “Control Register (Register 0),” page 120.)

2.During Auto-Negotiation, the contents of the Auto-Negotiation Advertisement Register are transferred to the link partner.

This register is writable through the MDIO, therefore enabling software control of the systems advertised abilities. See “Auto-Negotiation Advertisement Register (Register 4),” page 124 for more information.

Information provided in this register includes:

♦Fault Condition signaling

♦Duplex Mode

♦Flow Control capabilities for the attached MAC.

3.The advertised abilities of the Link Partner are simultaneously transferred into the Auto-Negotiation Link Partner Ability Base Register.

This register contains the same information as in the Auto-Negotiation Advertisement Register. See “Auto-Negotiation Link Partner Ability Base Register (Register 5),” page 125 for more information.

4.Under normal conditions, this completes the Auto-Negotiation information exchange.

It is now the responsibility of system management (for example, software running on an embedded PowerPCTM or MicroBlazeTM) to complete the cycle. The results of the Auto-Negotiation should be read from Auto-Negotiation Link Partner Ability Base Register. Other networking components, such as an attached Ethernet MAC, should be configured accordingly. See “Auto-Negotiation Link Partner Ability Base Register (Register 5)” for more information.

There are two methods that a host processor uses to learn of the competition of an Auto-Negotiation cycle:

♦Polling the Auto-Negotiation completion bit 1.5 in the Status Register (Register 1).

♦Using the Auto-Negotiation interrupt port of the core (see “Using the Auto- Negotiation Interrupt,” page 156).

154	www.xilinx.com	Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
		UG155 March 24, 2008