10/100 Mbps LAN Physical Layer Interface Datasheet

82555 — Networking Silicon

Datasheet

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

8.2 Parallel 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-

4 10BASE-T Full Duplex

5 10BASE-T Half Duplex

Table 5. Technology Priority

Priority Technology