Xilinx 1000BASE-X User Manual
Page 154
154
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.
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),”
.)
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
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
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
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