SNLS614A September 2018 – December 2018 DP83869HM
The DP83869HM 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, (and channel C and D in 1000BASE-T mode). 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 be enabled or disabled by strap, using the AMDIX Disable strap, or by register configuration, using bit 6 of the PHYCR register (address 0x0010). When Auto-MDIX is disabled, the PMA is forced to either MDI (straight) or MDIX (crossed). Manual configuration of MDI or MDIX can also be accomplished by strap, using the Force MDI/X strap, or by register configuration, using bit 5 of the PHYCR register.
For 10/100, Auto-MDIX is independent of Auto-Negotiation. Auto-MDIX works in both Auto-Negotiation mode and manual forced speed mode.