Cirrus-logic CS4202 User Manual download pdf (Page 13)

CS4202

DS549PP2 13

2.2 Control Registers

The CS4202 contains a set of AC ’97 compliant

control registers, and a set of Cirrus Logic defined

control registers. These registers control the basic

functions and features of the CS4202. Read access-

es of the control registers by the AC ’97 controller

are accomplished with the requested register index

in Slot 1 of a SDATA_OUT frame. The following

SDATA_IN frame will contain the read data in Slot

2. Write operations are similar, with the register in-

dex 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 descriptions

are found in Section 4, Register Interface.

2.3 Sample Rate Converters

The sample rate converters (SRC) provide high ac-

curacy digital filters supporting sample frequencies

other than 48 kHz to be captured from the CS4202

or played from the controller. AC ’97 requires sup-

port for two audio rates (44.1 and 48 kHz). In addi-

tion, the Intel

I/O Controller Hub (ICHx)

specification [9] requires support for five more au-

dio rates (8, 11.025, 16, 22.05, and 32 kHz). The

CS4202 supports all these rates, as shown in

Table 10 on page 32.

2.4 Mixers

The CS4202 input and output mixers are illustrated

in Figure 8. The stereo input mixer sums together

the analog inputs to the CS4202 according to the

settings in the volume control registers. The stereo

output mixer sums the output of the stereo input

mixer with the PC_BEEP and PHONE signals. The

stereo output mix is then sent to the LINE_OUT

and HP_OUT pins of the CS4202. The mono out-

put mixer generates a monophonic sum of the left

and right audio channels from the stereo input mix-

er. The mono output mix is then sent to the

MONO_OUT pin on the CS4202.

2.5 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

transmitted to the controller by means of the

AC-link SDATA_IN signal.

2.6 Volume Control

The CS4202 volume registers control analog input

levels to the input mixer and analog output levels,

including the master volume level. The PC_BEEP

volume control uses 3 dB steps with a range of 0 dB

to -45 dB attenuation. All other analog volume con-

trols use 1.5 dB steps. The analog inputs have a

mixing range of +12 dB signal gain to -34.5 dB sig-

nal attenuation. The analog output volume controls

have a range of 0 dB to -46.5 dB attenuation for

LINE_OUT, HP_OUT and MONO_OUT.

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Cirrus-logic CS4202 User Manual Page 13

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