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 IEEE 802.3-2008 Specification (the an_sync_status variable).