
256
Registers
Chapter 4
AMD-8111 HyperTransport I/O Hub Data Sheet
24674
Rev. 3.00
April 2003
AMD Preliminary Information
AC
‘
97 Audio Controller Microphone In Descriptor Shadow
DevB:5x48
Default:
0000_0000h
Attribute:
Read-only
AC
‘
97 Audio Controller General Control
DevB:5x4C
Default:
00h
Attribute:
See below
4.8.1.2
AC '97 Audio Mixer Registers
The audio mixer registers are physically located in the codec. Accesses to these registers are
forwarded through the AC link to the codec. Writes to a codec are completed when the data are
inserted in the output slot. Reads from a codec may cause a PCI retry cycle. For more information
about these registers see the AC '97 spec.
Table 61 on page 256 shows the register address space for the audio mixer registers. These registers
are exposed in I/O space. The base address register for these registers is DevB:5x10.
Table 61.
Audio Mixer Register
Bits
31:1
0
Description
DESCR. Descriptor current value
. This is a test register for reading the current descriptor value.
Read-only.
Bits
7:3
2
Description
Reserved
SWLSB. Subwoofer is LSB
.Read-write. When cleared to 0b the Center Front channel sample is
always placed in the least signi
fi
cant sample of the Subwoofer/Center Front information pair, i.e., the
audio data stream as represented in the host memory buffer pages must start with a Center Front
channel sample. When set to 1b the Subwoofer channel sample is always placed in the least
signi
fi
cant sample of the Center Front/Subwoofer information pair, i.e., the audio data stream as
represented in the host memory buffer pages must start with a Subwoofer channel sample.
RRLSB. Right Rear is LSB
. Read-write. When cleared to 0b the Left Rear channel sample is always
placed in the least signi
fi
cant sample of the Right Rear/Left Rear information pair, i.e., the audio data
stream as represented in the host memory buffer pages must start with a left rear channel sample.
When set to 1b the Right Rear channel sample is always placed in the least signi
fi
cant sample of the
Right Rear/Left Rear information pair, i.e., the audio data stream as represented in the host memory
buffer pages must start with a Right Rear channel sample.
RFLSB. Right Front is LSB
. Read-write. When cleared to 0b the left channel sample is always
placed in the least signi
fi
cant sample of the stereo information pair, i.e., the stereo audio data stream
as represented in the host memory buffer pages must start with a left channel sample. When set to 1b
the right channel sample is always placed in the least signi
fi
cant sample of the stereo information pair,
i.e., the stereo audio data stream as represented in the host memory buffer pages must start with a
right channel sample.
1
0
Address
Audio Mixer Registers
Primary
Secondary
1