
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
128
Datasheet
Document Number: 249241
Revision Number: 010
Revision Date: 30-May-2006
Intel recommends that a minimum recovery time be allowed after bringing up a port from software
4.5.5
Hardware Configuration Settings
The LXT9785/LXT9785E provides a hardware option to set the initial device configuration. The
hardware option uses three Global CFG pins that provide control for all ports (see
Table 42).
4.6
Link Establishment
4.6.1
Auto-Negotiation
The LXT9785/LXT9785E attempts to auto-negotiate with its link partner by sending Fast Link
Pulse (FLP) bursts. Each burst consists of 33 link pulses 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 LXT9785/LXT9785E also supports the optional “Next Page” function
(registers 7 and 8).
4.6.1.1
Base Page Exchange
By exchanging Base Pages, the LXT9785/LXT9785E 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.
Table 42. Global Hardware Configuration Settings
Desired Mode
CFG
Pin Settings
1
Resulting Register Bit Values
AutoNeg
Speed
Duplex
1
2
3
0.12
0.13
0.8
4.8
4.7
4.6
4.5
Disabled
10
Half
Low
0
N/A
Auto-Negotiation
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Full
High
Low
High
1
100
Half
Low
High
Low
1
0
Full
High
1
Enabled
100
Half
High
Low
1
10
0
1
00
Full/Half
High
Low
High
1
0
1
10/100
Half
High
Low
1
0
1
0
1
Full/Half
High
1
0
1