A block diagram of the 1G/10G/25G Ethernet Subsystemwith Auto-Negotiation (AN) with Parallel Detection (PD) is shown in the following figure. The Parallel Detection is done inside the AN RTL, which is encrypted. As a result of PD, only the AN is resolved to 1G speed.
The auto-negotiation function allows an Ethernet device to advertise the modes of operation it possesses to another device at the remote end of a backplane Ethernet link and to detect corresponding operational modes the other device might be advertising. The objective of this auto-negotiation function is to provide the means to exchange information between two devices and to automatically configure them to take maximum advantage of their abilities. It has the additional objective of supporting a digital signal detect to ensure that the device is attached to a link partner rather than detecting a signal due to crosstalk. When auto-negotiation is complete, ability is reported according to the available modes of operation.When Auto-Negotiation is complete, the datapath is switched to mission mode (the PCS), as shown in the preceding figure.