SNLS638A December 2018 – August 2019 DP83825I
The DP83825I can determine if a “straight” or “crossover” cable is used to connect to the link partner. It can automatically re-assign channel A and B to establish link with the link partner. Auto-MDIX resolution precedes the actual Auto-Negotiation process that involves exchange of FLPs to advertise capabilities. Automatic MDI/MDIX is described in IEEE 802.3 Clause 40, section 40.8.2. It is not a required implementation for 10BASE-Te and 100BASE-TX. Auto-MDIX can also be used when operating the PHY in Forced modes.
Auto-MDIX can be enabled or disabled in hardware, using the hardware bootstrap, or by register configuration, using bit of the PHY Control Register (PHYCR, address 0x0019). When Auto-MDIX is disabled, the PMA is forced to either MDI (“straight”) or MDIX (“crossover”). Manual configuration of MDI or MDIX can also be accomplished using register configuration, using bit of the PHYCR.