82551IT Datasheet, PDF (32/102 Pages) Intel Corporation – Fast Ethernet PCI Controller

82551IT — Networking Silicon
5.3.1.2
5.3.1.3
5.3.1.4
clock signal suspension using the Clockrun signal mechanism. The 82551IT supports a dynamic
standby mode. In this mode, the 82551IT is able to save almost as much power as it does in the
static power-down states. The transition to or from standby is done dynamically by the 82551IT
and is transparent to the software.
D1 Power State
For a device to meet the D1 power state requirements, as specified in the Advanced Configuration
and Power Interface (ACPI) Specification, Revision 1.0, it must not allow bus transmission or
interrupts; however, bus reception is allowed. Therefore, device context may be lost and the
82551IT does not initiate any PCI activity. In this state, the 82551IT responds only to PCI accesses
to its configuration space and system wake-up events.
The 82551IT retains link integrity and monitors the link for any wake-up events such as wake-up
packets or link status change. Following a wake-up event, the 82551IT asserts the PME# signal to
alert the PCI system.
D2 Power State
The ACPI D2 power state is similar in functionality to the D1 power state. If the bus is in the B2
bus power state, the 82551IT will consume less current than it does in the D1 state. In addition to
D1 functionality, the 82551IT can provide a lower power mode with wake-on-link status change
capability. The 82551IT may enter this mode if the link is down while the 82551IT is in the D2
state. In this state, the 82551IT monitors the link for a transition from an invalid link to a valid link.
The 82551IT will not attempt to keep the link alive by transmitting idle symbols or link integrity
pulses.¹ The sub-10 mA state due to an invalid link can be enabled or disabled by a configuration
bit in the Power Management Driver Register (PMDR).
D3 Power State
In the D3 power state, the 82551IT has the same capabilities and consumes the same amount of
power as it does in the D2 state. However, it enables the PCI system to be in the Bus Power 3 (B3)
state. If the PCI system is in the B3 state (in other words, no PCI power is present), the 82551IT
provides wake-up capabilities if it is connected to an auxiliary power source in the system. If
PME# is disabled, the 82551IT does not provide wake-up capability or maintain link integrity. In
this mode, the 82551IT consumes minimal power.
The 82551IT enables a system to be in a sub-5 watt state (low power state) and still be virtually
connected. More specifically, the 82551IT supports full wake-up capabilities while it is in the D3
cold state. The 82551IT can be connected to an auxiliary power source (V_AUX), which enables it to
provide wake-up functionality while the PCI power is off. The typical current consumption of the
82551IT is 125 mA at 3.3 V and a dual power plane is not required. If connected to an auxiliary
power source, the 82551IT receives all of its power from the auxiliary source in all power states.
When connected to an auxiliary power supply, the 82551IT must have a status indicator of whether
the power supply is valid (in other words, auxiliary power is stable). The indication is received at
the AUXPWR pin, as described next.
1. For a topology of two 82551IT devices connected by a crossed twisted-pair Ethernet cable, the deep power-down mode should be disabled.
If it is enabled, the two devices may not detect each other if the operating system places them into a low power state before both nodes
become active.
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Datasheet