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Intel® ICH5 AC ’97 Controller Theory of Operation
R
34 AC ’97 Programmer’s Reference Manual
Table 17. Power State Mapping for Modem in Dual Codec Desktop Transition
PR<A:D> + MLNK
(other power control (PRx) bits do not apply for Intel
®
ICH5
implementation)
+12 +5
from
+12
+3.3
Digital
+3.3
Vaux
Digital
Comments
Sdata_In D
A
C
1
A
D
C
1
Vref GPIO
Device State MLNK D C B A
D0 0 0 0 0 0 On On On On All on
D1 0 1 1 0 0 On On On On -DAC, -ADC
D2 0 1 1 0 0 On On On On Same as D1
D3
(wake-up on
ring)
1 1 1 0 0 Off Off Off On -Sdata_In,
D3 1 1 1 1 1 Off Off Off On -Sdata_In,
-Vref, -GPIO
Table 15 and Table 16 above, represent the recommended Power Transition Tables for a Desktop
System. The tables above preclude the need for a driver to provide codec topology detection
simplifying the initialization sequence. These tables do not provide the maximum power saving.
However, they are believed to provide sufficient power saving for the Desktop applications. The
OEM and IHV are free to provide further differentiation by allowing the deeper power savings
obtained by identifying the codec Topology.
3.6.3 Power Management Topology Considerations
A set of drivers could always assume Configuration Numbers 3 and 4, above, and establish their
power management policy based on Table 15 and Table 16. These are the safest configurations
with a semi-aggressive power management style consistent with a desktop environment. However,
even in a desktop environment, further power savings are possible when in Single Codec
Configurations Numbers 1 and 2. For the tables above to be implemented, the audio driver needs
to be able to determine the AC-link topology configuration.
3.6.3.1 Determining the Presence of Secondary and Tertiary Codecs
To determine that optional secondary and tertiary codecs are present, the driver needs to check
three Codec Ready bits located in the Global Status Register at:
Codec Ready: I/O Address: MBBAR + 30h (MBAR +40h) bits 8,9,28
If two of these three bits are set to 1, it indicates that a secondary codec is active in the AC-link.
If all three of these bits are set to 1, it indicates that a tertiary codec is active in the AC-link.