Intel 82555 manual Parallel Detect and Auto-Negotiation, Priority

Models: 82555

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82555 — Networking Silicon

Table 5. Technology Priority

Priority

Technology

410BASE-T Full Duplex

510BASE-T Half Duplex

To detect the correct technology, the two register fields should be ANDed together to obtain the highest common denominator. This value should then be used to map into a priority resolution table used by the MAC driver to use the appropriate technology.

The following is an outline of the Auto-Negotiation process:

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.Determine operating mode via the priority table

6.Receive FLP from the link partner and record FLP in the MII register

8.2Parallel Detect and Auto-Negotiation

The 82555 automatically determines the speed of the link either by using Parallel Detect or Auto- Negotiation. Upon a reset, a link status fail, or a negotiate/renegotiate command, the 82555 inserts a long delay during which no link pulses are transmitted. This period, known as Force_Fail, insures that the 82555’s link partner has gone into a Link Fail state before Auto-Negotiation or Parallel Detection begins. Thus, both sides (the 82555 and the 82555’s link partner) will perform Auto-

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Datasheet

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Intel 82555 manual Parallel Detect and Auto-Negotiation, Priority