SLXT973QE Cortina Systems Inc, SLXT973QE Datasheet - Page 33

• Manufacturer Part Number: SLXT973QE
• Manufacturer: Cortina Systems Inc

Specifications of SLXT973QE

• Lead Free Status / RoHS Status: Not Compliant

LXT973 Transceiver
Datasheet
249426, Revision 6.0
13 July 2007
3.6
3.6.1
3.6.1.1
3.6.1.2
3.6.1.3
3.6.1.4
Cortina Systems
Link Establishment
Auto-Negotiation
The LXT973 Transceiver attempts to auto-negotiate with its link partner by sending Fast
Link Pulse (FLP) bursts. Each burst consists of 33 pulse positions spaced 62.5 μs apart.
Odd link pulses (clock pulses) are always present. Even link pulses (data pulses) may
also be present or absent to indicate a “1” or a “0”. Each FLP burst exchanges 16 bits of
data, referred to as a “page.” All devices that support auto-negotiation must implement the
“Base Page”, defined by IEEE 802.3 (Registers 4 and 5). The LXT973 Transceiver also
supports the optional “Next Page” function (Registers 7 and 8).
Base Page Exchange
By exchanging Base Pages, the LXT973 Transceiver and its link partner communicate
their capabilities to each other. Both sides must receive at least three identical base pages
for negotiation to proceed. Each side finds their highest common capabilities, exchange
more pages, and agree on the operating state of the line.
Next Page Exchange
Additional information, exceeding that required by Base Page exchange, can also be sent
via “Next Pages.” The LXT973 Transceiver fully supports the IEEE 802.3 method of
negotiation via Next Page exchange. The Next Page exchange uses Register 7 to send
information and Register 8 to receive information, and occurs only if both ends of the link
advertise their ability to exchange Next Pages. The LXT973 Transceiver is configured to
make Next Page exchange easier for software. When a Base Page or Next Page is
received, the Page Received Register bit 6.1 remains set until read. When Register bit 6.2
(Next Page Able) is received, it stays set until read. This bit should be cleared whenever a
new negotiation occurs. This prevents the user from reading an old value in Register 6
and assuming there is valid information in Registers 5 and 8. Additionally, Register 6
contains a new bit (Register bit 6.5) that indicates when the current Received Page is the
Base Page. This information is useful for recognizing when next pages must be re-sent
due to the start of a new negotiation process. Register bit 16.1 and the Page Received bit
(Register bit 6.1) are also cleared upon reading Register 6.
Controlling Auto-Negotiation
When auto-negotiation is controlled by software, the following steps are recommended:
Link Criteria
In 100 Mbps mode, link is established when the scrambler becomes locked and remains
locked for approximately 50 ms. Link remains up unless the de-scrambler receives less
than 12 consecutive IDLE symbols in any 2 ms period. This provides a very robust
operation, filtering out any small noise hits that may disrupt the link.
In 10 Mbps mode, link is established based on the link state machine found in the IEEE
802.3, Clause 14.X specification. Receiving 100 Mbps idle patterns does not bring up a
10 Mbps link.
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3. After power-up, power-down, or reset, the power-down recovery time (max = 300 μs)
4. Set the auto-negotiation advertisement register bits.
5. Enable auto-negotiation (set MDIO Register bit 0.12 = 1).
LXT973 10/100 Mbps Dual-Port Fast Ethernet PHY Transceiver
must be exhausted before proceeding.
3.6 Link Establishment
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