LAN7430 datasheet(43/77 Pages) MICROCHIP

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DS00002631D-page 43

LAN7430/LAN7431

PME wakeup is enabled via the PME_En field in the PCIe Power Management Control/Status configuration register.

Although this does not directly affect the power state transitions, it does affect the allowable current draw while in certain

states. As an alternate, the Aux Power PM Enable field in the PCIe Device Control configuration register also allows

current draw while in certain states without enabling the PME function.

6.13.1.1

D0 is divided into two distinct substates, the “un-initialized” substate and the “active” substate. When a component

comes out of Conventional Reset, all Functions of the component enter the D0uninitialized (D0u) state. When a Function

completes FLR, it enters the D0u state. After configuration is complete, a Function enters the D0active (D0a) state, the

fully operational state for a PCI Express Function. A Function enters the D0a state whenever any single or combination

of the Function’s Memory Space Enable, I/O Space Enable, or Bus Master Enable bits have been set.

6.13.1.2

D3 support is required (both the D3cold and the D3hot states). Functions supporting PME generation from D3 must sup-

port it for both D3cold and the D3hot states.

Functional context is required to be maintained by Functions in the D3hot state if the No_Soft_Reset field in the PCIe

Power Management Control/Status configuration register is Set. In this case, software is not required to re-initialize the

Function after a transition from D3hot to D0 (the Function will be in the D0active state). If the No_Soft_Reset bit is Clear,

functional context is not required to be maintained by the Function in the D3hot state. As a result, in this case software

is required to fully re-initialize the Function after a transition to D0 as the Function will be in the D0uninitialized state.

The Function will be reset if the Link state has transitioned to the L2/L3 Ready state regardless of the value of the No_-

Soft_Reset bit.

6.13.1.2.1

D3hot

While in the D3hot state, a Function must not initiate any Request TLPs on the Link with the exception of a PME Mes-

sage. Completion TLPs may still be sent.

Configuration and Message requests are the only TLPs accepted by a Function in the D3hot state. All other received

Requests must be handled as Unsupported Requests, and all received Completions may optionally be handled as

Unexpected Completions.

If an error caused by a received TLP (e.g., an Unsupported Request) is detected while in D3hot, and reporting is enabled,

the Link must be returned to L0 if it is not already in L0 and an error Message must be sent. If an error caused by an

event other than a received TLP (e.g., a Completion Timeout) is detected while in D3hot, an error Message may option-

ally be sent when the Function is programmed back to the D0 state. Once in D3hot the Function can later be transitioned

into D3cold (by removing power from its host component).

Note that D3hot is also a useful state for reducing power consumption by idle components in an otherwise running sys-

tem.

6.13.1.2.2

D3cold

A Function transitions to the D3cold state when its main power is removed. A power-on sequence with its associated

cold reset transitions a Function from the D3cold state to the D0uninititialized state. At this point, software must perform a

full initialization of the Function in order to re-establish all functional context, completing the restoration of the Function

to its D0active state. This device has the option to reset only the PCIe controller and maintain the device’s functional con-

text.

Functions that support wakeup functionality from D3cold must maintain their PME context for inspection by PME service

routine software during the course of the resume process. A Function’s PME assertion is acknowledged when system

software performs a “write 1 to clear” configuration transaction to the asserting Function’s PME_Status bit of its PCI-PM

compatible PCIe Power Management Control/Status configuration register.

An auxiliary power source must be used to support PME event detection within a Function, Link reactivation, and to

preserve PME context from within D3cold. Note that once the I/O Hierarchy has been brought back to a fully communi-

cating state, as a result of the Link reactivation, the waking agent then propagates a PME Message to the root of the

Hierarchy indicating the source of the PME event.

Note:

A Function remains in D0a even if these enable bits are subsequently cleared.

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