Intel PCI-X User Manual

185

Once the PHY completes auto-negotiation, it updates the various statuses in the PHY Status 

Register, Link Partner Ability Register (Base Page), Auto-Negotiation Expansion Register, and 

1000BASE-T Status Register. For 1000BASE-T operation, the Auto-Negotiation Expansion 
Register and the Link Partner Ability Register (Base Page) are updated. Speed, duplex, page 

received, and Auto-Negotiation completion statuses are also available in the PHY Specific Status 

Register (PSTATUS) and the PHY Interrupt Status Register (PINTS). 

For fiber, the CTRL.STATUS register will reflect link status.

Assuming normal MAC configuration, the MAC status register STATUS reports bits SPEED, FD 
(duplex/half indication), and LU (link up status) shortly after the PHY (or MAC, for fiber) 

completes auto-negotiation.

The Ethernet controller PHY automatically determines whether or not it needs to cross over 

between pairs as shown in the following table so that an external crossover cable is not required. If 
the PHY interoperates with a device that cannot automatically correct for crossover, the Ethernet 

controller PHY makes the necessary adjustment prior to commencing Auto-Negotiation. If the 

PHY operates with a device that implements MDI/MDI-X crossover, a random algorithm as 
described in IEEE 802.3 clause 40.4.4 determines which device performs the crossover.

When the Ethernet controller PHY interoperates with legacy 10BASE-T devices that do not 

implement Auto-Negotiation, the PHY follows the same algorithm as described above since link 

pulses are present. However, when interoperating with legacy 100BASE-TX devices that do not 
implement Auto-Negotiation (link pulses are not present), the Ethernet controller PHY uses signal-

detection to determine whether to crossover.

Auto MDI/MDI-X crossover is the default hardware configuration, but can be disabled via the 

PHY Specific Control Register bits 6:5 (PSCON).

The pin mapping in MDI/MDI-X modes are as follows:

MDI[0]+/-

BI_DA +/-

TX +/-

TX +/-

BI_DB +/-

RX +/-

RX +/-

MDI[1]+/-

BI_DB +/-

RX +/-

RX +/-

BI_DA +/-

TX +/-

TX +/-

MDI[2]+/-

BI_DC +/-

unused

unused

BI_DD +/-

unused

unused 

MDI[3]+/-

BI_DD +/-

unused

unused

BI_DC +/-

unused

unused