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154 www.xilinx.com Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
UG155 March 24, 2008
Chapter 10: Auto-Negotiation
R
a link segment (the link partner) and to detect corresponding operational modes that the
link partner advertises. Figure 10-1 illustrates 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 PowerPC
TM
or MicroBlaze
TM
) 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).