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Intel
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82575EB Gigabit Ethernet Controller — Power Management Interconnects
Intel
®
82575EB Gigabit Ethernet Controller 324632-003
Software Developer’s Manual and EEPROM Guide Revision: 2.1
220 January 2011
This avoids negotiating through the LPLU procedure a link speed that is not advertised by
the user.
The following table lists the link speed as a function of a power management state, link speed control,
and gigabit speed enabling:
The 82575 initiates auto-negotiation without a direct driver command in the following cases:
• When the state of 1000 Mb/s disable changes. For example, if 1000 Mb/s is disabled on D3 or Dr
entry (but not in D0a), the PHY auto negotiates on entry.
• When LPLU changes state with a change in PM state. For example, on transition from D0a without
LPLU to D3 with LPLU. Or, on transition from D3 w LPLU to D0 without LPLU.
• On a transition from D0a state to a non-D0a state, or from a non-D0a state to D0a state, and LPLU
is set.
7.4.0.3.2 D0a State
A power managed link speed control lowers link speed (and power) when the highest link performance
is not required. When it is enabled to this D0 Low Power Link Up mode, any link negotiation tries to
establish a low link speed, starting with an initial advertisement defined by software.
The D0 LPLU configuration bit enables D0 Low Power Link Up. Before enabling the feature, software
must advertise one of the following speed combinations: 10 Mb/s only, 10/100 Mb/s, or 10/100/1000
Mb/s.
When speed negotiation starts, the PHY tries to negotiate a speed based on the currently advertised
values. If link establishment fails, the PHY tries to negotiate with different speeds; it enables all speeds
up to the lowest speed supported by the partner. For example, the 82575 advertises
10 Mb only and the partner supports 1000 Mb only. After the first try fails, the 82575 enables 10/100/
1000 Mb/s and try again. The PHY continues to try and establish a link until it succeeds or until it is
instructed otherwise. In the second step (adjusting to partner speed), the PHY also enables parallel
detect, if needed. Automatic MDI/MDI-X resolution is done during the first auto-negotiation stage.
Power
Management
State
Low Power
Link Up
1000 Mb/s Disable Bits
PHY Speed Negotiation
Disable 1000
Disable 1000
in Non-D0a
D0a 0 0 X The PHY negotiates to the highest speed advertised (normal
operation).
1 The PHY negotiates to highest speed advertised except 1000
Mb/s.
1 0 X The PHY goes through the LPLU procedure, starting with the
advertised values.
1 The PHY goes through the LPLU procedure, starting with
advertised values but does not advertise 1000 Mb/s.
Non-D0a 0 0 0 The PHY negotiates to highest speed advertised.
0 1 The PHY negotiates to highest speed advertised except 1000
Mb/s.
1X
1 0 0 The PHY goes through the LPLU procedure, starting at 10
Mb/s.
0 1 The PHY goes through LPLU procedure, starting at 10 Mb/s
but does not advertise 1000 Mb/s.