Xilinx Virtex-4 User Manual page 152

Chapter 5: Miscellaneous Functions
2.
3.
4.
SGMII Standard
Figure 5-4
Virtex-4 FPGA
Ethernet 1000BASE-X
PCS/PMA or SGMII
Ethernet
Media
Access
Controller
Link Partner Ability
Host Interface
PowerPC/
MicroBlaze
EMAC#CLIENTANINTERRUPT
Processors
The SGMII capable PHY has two distinctive sides to auto-negotiation:
•
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152
During auto-negotiation, the contents of Register 4 (see
Advertisement Register (Register
can be written through the management interface, and enables software control of the
system's advertised abilities. Information provided in this register includes:
♦
Fault condition signalling
♦
Duplex mode
♦
Flow control capabilities for the attached Ethernet MAC.
At the same time, the advertised abilities of the Link Partner are transferred into
Register 5 (see Table 4-14,
(Register 5)"). This includes the same information as in Register 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 or MicroBlaze device) to complete the cycle. The results of the
auto-negotiation should be read from Register 5, and other networking components,
such as an attached Ethernet MAC, should be configured accordingly. There are two
methods by which a host processor may learn of the competition of an auto-
negotiation cycle:
♦
By polling the auto-negotiation completion bit 1.5 in Register 1 (see
"Status Register (Register
♦
By using the auto-negotiation interrupt port (see
Interrupt," page 153).
illustrates the operation of SGMII auto-negotiation.
Sub-Layer
Auto-Neg Adv
(Reg 4)
SGMII
Base (Reg5)
Figure 5-4: SGMII Auto-Negotiation Overview
The PHY performs auto-negotiation with its link partner using the relevant auto-
negotiation standard for the chosen medium (BASE-T auto-negotiation, illustrated in
Figure 5-4, uses a twisted copper pair medium). This resolves the operational speed
and duplex mode with the link partner.
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4)") are transferred to the link partner. This register
"Auto-Negotiation Link Partner Ability Base Register
1)").
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)
Embedded Tri-Mode Ethernet MAC User Guide
Table 4-13, "Auto-Negotiation
Table 4-11,
"Using the Auto-Negotiation
Link Partner
Twisted
Copper Auto-Neg Adv
Pair (Reg 4)
Link Partner Ability
Base (Reg5)
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