Cirrus Logic CS4297A - Manual (Page 11)

CS4297A
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data in its Slot 2. Write operations are similar, with
the register index in Slot 1 and the write data in Slot
2 of a SDATA_OUT frame. The function of each
input and output frame is detailed in Section 3,
AC Link Frame Definition. Individual register de-
scriptions are found in Section 4, Register Inter-
face.
2.3 Output Mixer
The CS4297A has two output mixers, illustrated in
Figure 8. The stereo output mixer sums together
the analog inputs to the CS4297A, including the
PC_BEEP and PHONE signals, according to the
settings in the volume control registers. The stereo
output mix is sent to the LINE_OUT and
ALT_LINE_OUT pins on the CS4297A. The
mono output mixer generates a monophonic sum of
the left and right channels from the stereo input
mixer. The mono output mix is sent to the
MONO_OUT output pin on the CS4297A.
2.4 Input Mux
The input multiplexer controls which analog input
is sent to the ADCs. The output of the input mux is
converted to stereo 18-bit digital PCM data and
sent to the controller by means of the AC-link
SDATA_IN signal.
2.5 Volume Control
The CS4297A volume registers control analog in-
put levels to the input mixer and analog output lev-
els, including the master volume level, and the
alternate volume level. The PC_BEEP volume con-
trol uses 3 dB steps with a range of 0 dB to -45 dB
attenuation. All other analog volume controls use
1.5 dB steps. The analog inputs have a mixing
range of +12 dB signal gain to -34.5 dB signal at-
tenuation. The analog output volume controls have
from 0 dB to -94.5 dB attenuation for LINE_OUT
and from 0 dB to -46.5 dB attenuation for
ALT_LINE_OUT and MONO_OUT.
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CS4297A