Answers Database
LogiCORE PCI: Power Management - Description of Function Power States
Record #3552
Product Family: Software
Product Line: LogiCore
Product Part: PCI Core Generator
Product Version: 2.0
Problem Title:
LogiCORE PCI: Power Management - Description of Function Power States
Problem Description:
Urgency: Standard
Problem Description:
From a power management perspective, a PCI device can support
up to 4 power management states. They are D0, D1, D2 and D3.
The higher the number of the state, the more aggressive the power
savings.
Solution 1:
D0:
All PCI functions must support the D0 state. D0 is simply
an 'ON' state, with two subsets: un initialized and initialized.
When the device is powered on, it is in the un initialized
state, and makes the transition to the initialized state after
being initialized by the system software.
D1:
Implementation of the D1 power management state is optional.
D1 is used as a light sleep state. Some functions may be
processing background tasks (i.e. monitoring the network, etc.)
which actually requires most of the function to be active. D1
state must respond to PCI configuration space access.
D2:
Implementation of the D2 power management state is optional.
When a PCI function is not currently being used and probably
will not been used for some time, it may be put into D2. This
state requires the function to provide significant power
savings. D2 state must respond to PCI configuration space
access.
Note: The PCI Power Management Spec. V1.1 is backwards
compatible with PCI specs. V2.0 and V2.1.
D3:
All PCI functions must support D3. This state has two
subsets: D3hot and D3cold. If a function is in D3hot then it
must respond to configuration space accesses as long as power
and clock are supplied so that they can be returned to D0 by
software. A function is in D3cold simply if Vcc is removed
from it.
End of Record #3552 - Last Modified: 07/30/99 16:38 |
