3.0 Electrical Interfaces
Fusion 878A
3.6 Power Management Interface
PCI Video Decoder
3-28
Conexant
100600B
3.6 Power Management Interface
Fusion 878A supports the new capabilities feature for power management as
outlined in
PCI Bus Power Management Interface Specification
,
Revision 1.1
.
Power management states D0, D3
hot
and D3
cold
are supported. Optional power
states D1 and D2 are not supported since there is no significant power savings
without going to D3. Restoring a function from D1 or D2 would also require
device specific interaction that the operating system does not currently support.
3.6.1 PME#
The Power Management Event signal PME# is not used since wake-up events are
not generated by the Fusion 878A.
3.6.2 D3 Power States
Fusion 878A supports D0 (on) and D3
cold
(off) by default. Each function also
supports D3
hot
independently. When placing a function in D3
hot
, the operating
system is required to disable I/O and memory space as well as bus mastering via
the PCI Command register. Restoring a function from D3 requires the operating
system to re-initialize the function. Full context must be restored before the
function is capable of resuming normal operation.
Functions in D3
hot
respond to configuration space accesses as long as the
power and clock are supplied. In addition to each function being disabled from
memory access and bus mastering, the D3
hot
power state will enable extra power
savings by powering down as many circuits as possible. The video function will
disable the VFE (sleep A/Ds, disable AGC), PLL, and decoder clocks (gate off
XTAL signals in CLKIOGEN). The audio function will disable its clock as well
as the AFE. In addition each function will reset as many circuits as possible
without disabling configuration access.