Auto-negotiation with parallel detection architecture for different data rates

A physical (PHY) circuit, comprising:

• a Physical Medium Dependent (PMD) circuit, the PMD circuit having a receiver and a transmitter;
• a Physical Medium Attachment (PMA) circuit coupled to the PMD circuit;
• a plurality of Physical Coding Sublayer (PCS) circuits coupled to the PMA circuit, wherein each PCS circuit is configured to implement a different communication protocol;
• and
• an auto-negotiation circuit coupled to the PMD circuit, wherein the auto-negotiation circuit is configured to determine a selected communication protocol compatible with a link partner device from a plurality of communication protocols by:
• configuring the receiver to operate at a first data rate corresponding to a first communication protocol and connecting the receiver with a first PCS circuit corresponding to the first communication protocol;
• in response to determining that the link partner device is incompatible with the first communication protocol during a first time window, configuring the receiver to operate at a second data rate corresponding to a second communication protocol and connecting the receiver with a second PCS circuit corresponding to the second communication protocol;
• and
• monitoring for compatibility of the link partner device with the second communication protocol during a second time window;
• wherein the second data rate is different than the first data rate and the second communication protocol is distinct from the first communication protocol.