LXT971ABC datasheet(31/90 Pages) INTEL

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LXT971A 3.3V Dual-Speed Fast Ethernet Transceiver

Datasheet

Document #: 249414

Revision #: 002

Rev. Date: August 7, 2002

3.5

Establishing Link

See Figure 9 for an overview of link establishment.

3.5.1

Auto-Negotiation

If not configured for forced operation, the LXT971A attempts to auto-negotiate with its link

partner by sending Fast Link Pulse (FLP) bursts. Each burst consists of up to 33 link pulses spaced

62.5

µs apart. Odd link pulses (clock pulses) are always present. Even link pulses (data pulses) may

be present or absent to indicate a “1” or a “0”. Each FLP burst exchanges 16 bits of data, which are

referred to as a “link code word”. All devices that support auto-negotiation must implement the

“Base Page” defined by IEEE 802.3 (registers 4 and 5). LXT971A also supports the optional “Next

Page” function as described in Tables 50 and 51 on page 80 (registers 7 and 8).

3.5.1.1

Base Page Exchange

By exchanging Base Pages, the LXT971A and its link partner communicate their capabilities to

each other. Both sides must receive at least three identical base pages for negotiation to continue.

Each side identifies the highest common capabilities that both sides support and configures itself

accordingly.

3.5.1.2

Next Page Exchange

Additional information, above that required by base page exchange is also sent via “Next Pages”.

The LXT971A fully supports the IEEE 802.3ab method of negotiation via Next Page exchange.

3.5.1.3

Controlling Auto-Negotiation

When auto-negotiation is controlled by software, the following steps are recommended:

• After power-up, power-down, or reset, the power-down recovery time, as specified in Table 40

on page 70, must be exhausted before proceeding.

• Set the Auto-Negotiation Advertisement Register bits.

• Enable auto-negotiation (set MDIO Register bit 0.12 = 1).

3.5.2

Parallel Detection

For the parallel detection feature of auto-negotiation, the LXT971A also monitors for 10BASE-T

Normal Link Pulses (NLP) and 100BASE-TX Idle symbols. If either is detected, the device

automatically reverts to the corresponding operating mode. Parallel detection allows the LXT971A

to communicate with devices that do not support auto-negotiation.

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