STAC9708 Datasheet, PDF (34/56 Pages) List of Unclassifed Manufacturers – Multi-Channel AC97 Codec With Multi-Codec Option

SigmaTel, Inc.
Preliminary
STAC9708/11
NOTE: The lower half of the Vendor ID2 register (index 7Eh) currently contains the value 08h
identifying the STAC9708/11. This value can be used by the audio driver, or miniport driver in the
case of WIN98^®, to adjust software functionality to match the feature-set of the STAC9708/11. This
portion of the register will likely contain different values if the software profile of the STAC9708/11
changes, as in the case of silicon level device modifications. This will allow the software driver to
identify any required operational differences between the existing STAC9708/11 and any future
versions.
5. LOW POWER MODES
The STAC9708/11 is capable of operating at reduced power when no activity is required. The state of power
down is controlled by the Powerdown Register (26h). There are 7 commands of separate power down. The
power down options are listed in Table 18. The first three bits , PR0..PR2, can be used individually or in
combination with each other, and control power distribution to the ADC’s, DAC’s and Mixer. The last analog
power control bit, PR3, affects analog bias and reference voltages, and can only be used in combination with PR1,
PR2, and PR3. PR3 essentially removes power from all analog sections of the codec, and is generally only
asserted when the codec will not be needed for long periods. PR0 and PR1 control the PCM ADC’s and DAC’s
only. PR2 and PR3 do not need to be "set" before a PR4, but PR0 and PR1 must be "set" before PR4.
Table 20. Low Power Modes
GRP BITS
FUNCTION
PR0
PCM in ADC’s & Input Mux Powerdown
PR1
PCM out DACs Powerdown
PR2
Analog Mixer powerdown (Vref still on)
PR3
Analog Mixer powerdown (Vref off)
PR4
Digital Interface (AC-Link) powerdown (extnl clk off)
PR5
Internal Clk disable
PR6
Not implemented
PRJ
Powerdown Surround DACs
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10/02/98