February, 2007
Device Power States
10.1.1
Device Power States
The PEX 8532 supports the PCI Express PCI-PM D0, D3hot, and D3cold (no VAUX) Device Power
Management states. The D1 and D2 states, which are optional in the PCI Express Base r1.0a, are
not supported by the PEX 8532.
The D3hot state can be entered from the D0 state, when system software programs the Power
Management Status and Control register Power State field (offset 44h[1:0]=11b) for the appropriate
port. The D0_uninitialized state can be entered from the D3hot state when the upstream and downstream
links are in the L0s state and system software clears the Power Management Status and Control
register Power State field (offset 44h[1:0]=00b).
10.1.1.1
D0 State
D0 is divided into two distinct substates – uninitialized and active. When power is initially applied to a
PCI Express component, it defaults to the D0_uninitialized state. The component remains in the
D0_uninitialized state until the serial EEPROM load completes.
A device enters the D0_active state when:
• Any single Memory Access Enable occurs
• System software sets any combination of the Command register Bus Master Enable, Memory
Access Enable, and/or I/O Access Enable bits (offset 04h[2, 1, and/or 0], respectively)
10.1.1.2
10.1.1.3
D3hot State
A device in the D3hot state must be able to respond to Configuration accesses, allowing transition by
software to the D0_uninitialized state. Once in the D3hot state, the device can later be transitioned into
the D3cold state by removing power from the device. In the D3hot state, Hot Plug operations cause
a PME in the PEX 8532.
D3cold State
The PEX 8532 transitions to the D3cold state when power is removed. Re-applying power causes the
PEX 8532 to transition from the D3cold state into the D0_uninitialized state, followed by a
configuration and link training sequence. The D3cold state assumes that all previous context is lost;
therefore, software must save the required context while the PEX 8532 remains in the D3hot state.
The PEX 8532 does not support AUX-Power; therefore, PME generation from D3cold
is not supported.
ExpressLane PEX 8532AA/BA/BB/BC 8-Port/32-Lane Versatile PCI Express Switch Data Book
Copyright © 2007 by PLX Technology, Inc. All Rights Reserved – Version 1.6
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