Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0
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If the modem Codec has been enabled to wake the system, and a power management event occurs (such as the
phone ringing), then the modem Codec complies with the behavior specified in Section 6.5.2.
7.3.2 Secondary MC’97 Codec and MLNK
Setting the MLNK bit when transitioning a Secondary modem Codec to the D3
hot
state requires different behavior
from the modem Codec than what is required from a Primary modem Codec.
The potential for subsequent Primary audio Codec activity requires that a Secondary modem Codec must continue to
be an active participant on the AC-link as long as the AC-link continues to transact I/O frames. If enabled to
generate a wake event while MLNK is set while the AC-link is still transacting I/O frames, the modem Codec must
pass the GPI (Ring Indication) information normally over its SDATA_IN signal within slot 12.
If the AC-link is programmed to a PR4
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(AC-link halted with BIT_CLK held low) the Secondary Codec must be
able to detect this (e.g. one way is to snoop a writes to the Primary Codec Register 26h PR4 bit) and must, upon
detecting this, drive and hold its SDATA_IN signal low. If enabled to wake-on-ring, the appropriate GPI assertion
shall cause the modem Codec to transition its SDATA_IN signal from low to high signaling the wake request.
If the AC-link is transitioned to a D3
cold
state (i.e., power removed) subsequent to the MLNK bit having been set ,
the modem must drive and hold its SDATA_IN signal low. If enabled to wake-on-ring, the appropriate GPI
assertion shall cause the modem Codec to transition its SDATA_IN signal from low to high signaling the wake
request. Detecting that the AC-link has transitioned to the D3
cold
state may be accomplished by sampling the AC-
link RESET# signal, given that whenever the AC-link is in the D3
cold
state RESET# is required to be actively
asserted.
Once the modem Codec’s SDATA_IN has been driven low for one of the two aforementioned reasons, it must
remain at a logic low level until one of three events happen:
1.
Low-to-high transition on AC-link RESET#
2.
Warm Reset sequence signaled on the AC-link
3.
A power management event occurs, such as a ring detection
The low-to-high transition of AC-link RESET# indicates resumption from the D3
cold
state where AC-link power had
been removed. The sampling of this transition on the RESET# signal must effectively be treated as if observing a
warm reset in the sense that no internal auxiliary powered state logic is impacted (i.e., reinitialized). Unaffected
logic must include, but not necessarily be limited to, wake event status and caller ID data if supported. Resumption
of normal AC-link activity must begin as though the Codec had been issued a warm reset semantic.
Warm Reset is the required resume sequence when the modem Codec has been resumed from a D3
hot
state where the
AC-link had been halted yet full power had been maintained. If the Secondary modem Codec observes a Warm
Reset sequence (i.e., SYNC assertion in the absence of BIT_CLK) the modem Codec shall resume normal internal
operation and begin communicating over the AC-link when ready.
If the modem Codec has been enabled to wake the system, and a power management event occurs (such as the
phone ringing), then the modem Codec shall comply with the behavior specified in Section 6.5.2.
7.4 Warm and Cold AC-link Reset Considerations
AC-link reset operations occur when the system is initially powered up, when resuming from a lower powered sleep
state, and in response to critical subsystem failures that can only be recovered from with a reset.
The following subsections focus on the behavior of the AC-link when resuming from a low power sleep state.
7.4.1 Resume Reset Behavior
The form of reset that is signaled (if necessary) when resuming the AC-link and its Codec(s) is dependent upon the
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Not recommended for multiple, audio + modem, Codec configurations. See Section 7.6.