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Independent Input Channels Capability
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AC ’97 Programmer’s Reference Manual 49
8 Independent Input Channels
Capability
ICH5 AC ’97 controller provides capability for two DMA channels dedicated to independent PCM
and Microphone audio streams. These allow improved features that enable applications such as
audio mobile docking and microphone arrays. Before the DMA transfer can occur software must
determine the proper codec topology in the AC-link in order to program proper volume values and
other relevant properties.
8.1 Link Topology Determination
While the SDATA_Out lines are shared by all AC ’97 Component Specification, Revision 2.3-
compliant codecs, the input DMA engines must be properly steered to specific SDATA_IN[0:2]
lines on the link. Software must determine the specific codec ID assignment to the
SDATA_IN[0:2] lines to properly adjust codec properties for operation. Software must fill a table
similar to the following:
Table 26. Topology Descriptor
Input Channels SDATA_IN[0:2] Codec ID[00:10]
PCM IN & MIC ? ?
PCM IN 2 & MIC 2 ? ?
Software uses a recurrent algorithm using the SDATA_IN Map Register to determine the values
for the table above.
MBBAR + 80h: SDATA_IN Map Register.
Table 27. SDATA_IN Map
Bit Description
7:6
PCM In 2, Microphone In 2 Data In Line (D21L): When the SE bit is set, these bits indicates which
SDATA_IN line should be used by the hardware for decoding the input slots for PCM In 2 and
Microphone In 2. When the SE bit is cleared, the value of these bits are irrelevant, and PCM In 2 and
Mic In 2 DMA engines are not available.
00 SDATA_IN0
01 SDATA_IN1
10 SDATA_IN2
11 Reserved
5:4
PCM In 1, Microphone In 1 Data In Line (DI1L): When the SE bit is set, these bits indicates which
SDATA_IN line should be used by the hardware for decoding the input slots for PCM In 1 and
Microphone In 1. When the SE bit is cleared, the value of these bits are irrelevant, and the PCM In 1
and Mic In 1 engines use the OR’d SDATA_IN lines.
00 SDATA_IN0
01 SDATA_IN1
10 SDATA_IN2