When High, the link is valid and has remained valid after this register was last read; synchronization of the link has been obtained and Auto-Negotiation (if enabled) has completed.
When Low, either:
• A valid link has not been established; link synchronization has failed or Auto-Negotiation (if enabled) has failed to complete.
OR
• Link synchronization was lost at some point because this register was previously read. However, the current link status might be good. Therefore read this register a second time to get confirmation of the current link status.
Regardless of whether Auto-Negotiation is enabled or disabled, there can be some delay in the deassertion of Link Status following the loss of synchronization of a previously successful link. This is due to the Auto-Negotiation state machine which requires that synchronization is lost for an entire link timer duration before changing state. For more information, see the 802.3-2008 Specification [Ref 2] (the an_sync_status variable).