The following figure shows the operation of SGMII Auto-Negotiation as described in Overview of Operation.
Additional information about SGMII Standard Auto-Negotiation is provided in the following sections.
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 shown in the preceding figure, 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 core (in SGMII mode), by leveraging the 1000BASE-X Auto-Negotiation specification described in the 1000BASE-X Standard topic. 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
- The information exchanged is different and now contains speed resolution in addition to duplex mode. See Register 5: Auto-Negotiation Link Partner Base in Configuration and Status Register Map for 1G Ethernet PCS/PMA. Speed and Duplex status bits of this register are also provided in status_vector.
- There are no other differences and dealing with the results of Auto-Negotiation can be handled as described previously in the 1000BASE-X Standard topic.