CS4281 Programming Manual
DS308PRM1
63
Confidential Draft
3/7/00
9. PCI POWER MANAGEMENT
The CS4281 supports the PCI Bus Power Manage-
ment Interface Specification, version 1.1.
9.1
Power Management States
The PCI power management specification defines
four major power states: D0 (fully on), D1, D2, and
D3 (fully off). The D3 state is divided into two sub-
states, D3
hot
and D3
cold
; D3
cold
differs from D3
hot
in that the normal PCI bus V
cc
signals (not to be
confused with the V
AUX
signal) are turned off. The
D0 state is also divided into two sub-states, D0
active
and D0
uninitialized
; the D0
unitialized
state describes a
device that has just received a PCI
RST#
signal and
has not yet been programmed (and therefore it is
not consuming full power), while the D0
active
state
describes a device that has been programmed and is
fully operational (and therefore consumes full
power). The CS4281 can be in the D0
uninitialized
state when initial power is applied, or coming from
a D3 state. In D3
cold
,
VAUX
supplies power to al-
low power management events to occur where the
rest of the chip has power removed. The
RST#
sig-
nal will be active during this state and cannot reset
the registers and logic powered by
VAUX
.
The CS4281 supports all of the power states de-
fined in the PCI power management specification,
and provides bits in the EPPMC register that deter-
mine what gets powered down when in a particular
state. The default is to have the CS4281 do no pow-
er management when changing between states;
thereby having all power management controlled
through software. Assuming the CS4281 is pro-
grammed to manage power automatically, the fol-
lowing would be a typical configuration:
The DLL refers to the CS4281 internal clock de-
rived from the AC Link
ABITCLK
signal. See the
Clock Management section for full details. In D1
the DLL and Joystick are powered off but the AC
Link is still active. In D2, host software would also
power the AC Link down by programming the Co-
dec into a PR4 state. This would kill ABITCLK
and force the Codec into a fairly low-power mode.
In D3
hot
, the CS4281 is placed in its lowest power
state where the entire chip, except for Config space
accesses and the BIU) is powered down and all reg-
isters are reset to their default state. The Codec is
also held in reset using the
ARST#
pin. In D3
cold
,
VDD power is removed from the PCI bus and
VAUX
power may - optionally - be available. The
CS4281 and Codec are held in reset by the PCI
RST#
pin. By default, the power management bits
indicating support for D3
cold
and
VAUX
are false.
State
EPPMC Register Bits
Interpretation
D0
active
not applicable
DLL running: Normal operation
D0
unintialized
not applicable
DLL off, AC Link down: reset defaults
D1
D1DLL, D1JSD
DLL off: maintain context
D2
D2JSD, PR4*
DLL off, AC Link powered down: maintain context
D3
hot
D3FPD, D3ART
Chip in full reset (except config space): context lost
D3
cold
doesn’t matter
V
cc
off, V
AUX
active: context lost
* PR4 requires Host software to write a Codec Register to bring AC Link down. Brought back up through
SPMC.ASYN
.
Table 7. Power Management Typical Configuration
D
ra
ft
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