Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0
92
Audio Codec
D-State
Modem Codec
D-State
System State
(ACPI: S0-S5)
Resume activity Comments
D0 D0 S0 N/A Audio/Modem active; System is operating in
the Working State
D0 D1, D2 or D3hot S0 No reset; modem Codec
PR bits modified
Audio active, Modem idle; System is operating
in the Working State
D1 D0 S0 No reset; audio Codec PR
bits modified
Audio idle, modem active; System is operating
in the Working State
D1 D1, D2 or D3hot S0 or S1 No reset; audio and
modem PR bits modified
Both Codecs idle; System is either operating
in the Working State or in the S1 sleep state
D2 D0 S0 No reset; audio Codec PR
bits modified
Audio idle, modem active; System is operating
in the Working State
D2 D1, D2 or D3hot S0, S1, or S2 No reset; audio and
modem
Codec PR bits modified
Both Codecs idle; System is either operating
in the Working State, or in the S1 or S2 sleep
state
D3hot D0 S0 No reset; audio Codec PR
bits modified
Audio Codec idle, modem active; System is
operating in the Working State
(note audio Codec PR4 is prohibited in
Codec/system state as it would preclude
normal Secondary modem Codec operation)
D3hot D1, D2 or D3hot S0, S1, or S2 Warm Reset if audio PR4
bit is set; otherwise audio
and modem PR bits
modified only
Both Codecs idle; System is either operating
in the Working State, or in the S1 or S2 sleep
state
D3cold D3cold S3, S4, or S5 Cold reset to AC-link;
modem Codec must
interpret this as a warm
reset; full audio Codec
register and context
restoration, modem Codec
may need partial context
restoration
Deep sleep state, no power to audio Codec,
only auxilairy power to modem; modem may
be armed to answer the phone (except when
in ACPI S5)
Table 48. Resume Reset Behavior: Audio and Modem
7.4.2 Resuming Normal AC-link Operation from S3, S4 or S5 System Sleep
State
In accordance with prior revisions of the AC ‘97 specification, when the AC-link is unpowered, as is the case when
the system is in S3, S4 or S5, the AC-link RESET# output buffer is unpowered typically leaving the RESET# signal
floating at or near ground. Given the low active nature of AC-link RESET#, this presents a problem for modem
Codecs that must continue to operate under auxiliary power while the system sleeps. An auxiliary powered modem
Codec could be faced with what would appear to be a perpetual reset condition.
This issue is identical to the problem that any PCI-based D3
cold
/PME# capable function faced when the PCI bus was
programmed to B3 and the PCIRST# output buffer, being unpowered, floated around ground potential. Prior to the
3.3Vaux PCI-PM Specification updates, which require PCIRST# to be actively asserted whenever the PCI bus was
in the unpowered B3 state, these PCI functions can not determine whether or not a real reset had occurred or
whether the bus was unpowered and floating near ground potential.
7.4.2.1 AC-link RESET# SIGNALING REQUIREMENT
AC-link RESET# must be asserted, and actively held low whenever the system is in the S3, S4 or S5 state. Given
this DC ‘97 Controller provides that the AC-link RESET# signal remains low at these times, an auxiliary powered