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AMD SP5100 Databook
44409 Rev. 1.70 October 10
52
Functional Description
8.1.1 USB Power Management
An advanced power management capability interface compliant with
PCI Bus Power Management
Interface Specification Revision 1.1
is incorporated into the EHCI. This interface allows the EHCI to be
placed in various power management states, offering a variety of power savings for a host system.
highlights the EHCI support for power management states and features supported for each of
the power management states. An EHCI implementation may internally gate-off USB clocks and suspend
the USB transceivers (low power consumption mode) to provide these power savings.
Table 8-1: EHCI Support for Power Management States
PCI Power
Management State
State Required/
Optional by Spec
Comments
D0
Required
Supported in SP5100.
Fully awake backward compatible state. All logic in full power
mode.
D1
Optional
Not supported in SP5100.
USB Sleep state with EHCI bus master capabilities disabled. All
USB ports in suspended state. All logic in low latency power
saving mode because of low latency returning to D0 state.
D2
Optional
Not supported in SP5100.
USB Sleep state with EHCI bus master capabilities disabled. All
USB ports in suspended state.
D3hot
Required
Supported in SP5100.
Deep USB Sleep state with EHCI bus master capabilities
disabled. All USB ports in suspended state.
D3cold
Required
Supported in SP5100.
Fully asleep backward compatible state. All downstream devices
are either suspended or disconnected based on the
implementation’s capability to supply downstream port power
within the power budget.
The functional and wake-up characteristics for the EHCI power states are summarized in Table 8-2
below.
Table 8-2: EHCI Power State Summary
Power State
Functional Characteristics
Wake-up Characteristics (Associated Enables
must be Set)
D0
•
Fully functional EHCI device state
•
Unmasked interrupts are fully
functional
•
Resume detected on suspended port
•
Connect or Disconnect detected on port
Over Current detected on port
D1
•
EHCI shall preserve PCI
configuration
•
EHCI shall preserve USB
configuration
•
Hardware masks functional
interrupts
•
All ports are disabled or suspended
•
Resume detected on suspended port
•
Connect or Disconnect detected on port
•
Over Current detected on port
D2
•
EHCI shall preserve PCI
configuration
•
EHCI shall preserve USB
configuration
•
Hardware masks functional
interrupts
•
All ports are disabled or suspended
•
Resume detected on suspended port
•
Connect or Disconnect detected on port
•
Over Current detected on port