Data Sheet

Interconnects—Ethernet Controller I210

117

3.7.8.1.6 10/100 MB/s Mismatch Resolution

It is a common occurrence that a link partner (such as a switch) is configured for forced full-duplex

(FDX) 10/100 Mb/s operation. The normal auto-negotiation sequence would result in the other end

settling for half-duplex (HDX) 10/100 Mb/s operation. The mechanism described in this section resolves

the mismatch automatically and transitions the I210 into FDX mode, enabling it to operate with a

partner configured for FDX operation.

The I210 enables the system software device driver to detect the mismatch event previously described

and sets its duplex mode to the appropriate value without a need to go through another auto-

negotiation sequence or breaking link. Once software detects a possible mismatch, it might instruct the

I210 to change its duplex setting to either HDX or FDX mode. Software sets the Duplex_manual_set bit

to indicate that duplex setting should be changed to the value indicated by the Duplex Mode bit in PHY

Duplex_manual_set bit is set to 1b would also cause a change in the device duplex setting.

The Duplex_manual_set bit is cleared on all PHY resets, following auto-negotiation, and when the link

goes down. Software might track the change in duplex through the PHY Duplex Mode bit in Register 17

or a MAC indication.

3.7.8.1.7 Link Criteria

Once the link state is determined-via auto-negotiation, parallel detection or forced operation, the PHY

and its link partner bring up the link.

3.7.8.1.7.1 1000BASE-T

For 1000BASE-T links, the PHY and its link partner enter a training phase. They exchange idle symbols

and use the information gained to set their adaptive filter coefficients. These coefficients are used to

equalize the incoming signal, as well as eliminate signal impairments such as echo and cross talk.

Figure 3-17. Cross-Over Function

MDIX (Switch)

MDI (DTE/NIC)

Phy

CROSS(1:0) = 00

CROSS(1:0) = 01

Flat Cable