Intel 82558 Manuale Utente

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To detect the correct technology, the two register fields are ANDed together to obtain the highest 

common denominator. This value is used to map into a priority resolution table used by the MAC 
driver to select the appropriate technology. The auto-negotiation process occurs in the following 

steps:

1. Receive 3 consecutive, matching code words.

2. Set acknowledge bit in transmit code word.

3. Receive 3 consecutive, matching code words with acknowledge bit set.

4. Transmit 6 to 8 more code words with acknowledge bit set.

5. Use priority table to determine operating mode.

6. FLP received from link partner is recorded in MDI register.

The key to auto-negotiation’s interoperation with installed legacy LANs is the Parallel Detection 

function. Parallel Detection can be used to determine what the line speed is if the link partner does 
not support an N-Way (the FLP exchange is not supported) repeater or switch. Parallel Detection 

works by passing the signals present on the receiver to the 100BASE-TX and 100BASE-T4 link 

monitor functions. If one link monitor function indicates a valid link, then it connects that 
technology to the media.

The 82555 PHY and the 8255x (excluding the 82557) PHY modules support N-Way and Parallel 

Detection (in the event that their link partner does not respond to FLPs).

0

10BASE-T

1

10BASE-T Full Duplex

2

100BASE-TX

3

100BASE-TX Full Duplex

4

100BASE-T4

5

Reserved

6

Reserved

7

Reserved

1

100BASE-TX Full Duplex

2

100BASE-T4

3

100BASE-TX

4

10BASE-T Full Duplex

5

10BASE-T