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76 Programmer’s Reference Manual
AC ’97 Audio Controller Registers (D30:F2)
NOTE:
1. Software should not try to access reserved registers
2. Primary Codec ID cannot be changed. Secondary codec ID can be changed via bits 1:0 of configuration
register 40h. Tertiary codec ID can be changed via bits 3:2 of configuration register 40h.
3. The tertiary offset is only available through the memory space defined by the MMBAR register.
The Bus Master registers are located from offset + 00h to offset + 51h and reside in the AC ’97
controller. Accesses to these registers do not cause the cycle to be forwarded over the AC-link to
the codec. S/W could access these registers as bytes, word, DWord or qword quantities, but reads
must not cross DWord boundaries.
In the case of the split codec implementation, accesses to the different codecs are differentiated by
the controller by using address offsets 00h
–7Fh for the primary codec, address offsets 80h–FFh for
the secondary codec and address offsets 100h
–17Fh for the tertiary codec.
The Global Control (GLOB_CNT) (D30:F2:2Ch) and Global Status (GLOB_STA) (D30:F2:30h)
registers are aliased to the same global registers in the audio and modem I/O space. Therefore a
read/write to these registers in either audio or modem I/O space affects the same physical register.
Bus Mastering registers exist in I/O space and reside in the AC ’97 controller. The six channels,
PCM in, PCM in 2, PCM out, Mic in, Mic 2, and S/PDIF out, each have their own set of Bus
Mastering registers. The following register descriptions apply to all six channels. The register
definition section titles use a generic “x_” in front of the register to indicate that the register applies
to all six channels. The naming prefix convention used in Table 2-3 and in the register description
I/O address is as follows:
PI = PCM in channel
PO = PCM out channel
MC = Mic in channel
MC2 = Mic 2 channel
PI2 = PCM in 2 channel
SP = S/PDIF out channel.
5Ah DAh 15Ah Vendor Reserved
7Ch FCh 17Ch Vendor ID1
7Eh FEh 17Eh Vendor ID2
Table 2-2. Intel
®
ICH7 Audio Mixer Register Configuration
Primary Offset
(Codec ID =00)
Secondary Offset
(Codec ID =01)
Tertiary Offset
(Codec ID =10)
NAMBAR Exposed Registers
(D30:F2)