82C931 Datasheet, PDF (28/64 Pages) List of Unclassifed Manufacturers – Plug and Play Integrated Audio Controller

82C931
4.2 16-Bit Codec/Mixer
4.2.1 Codec
Features of the built-in 16-bit stereo sigma-delta codec
include:
• Sigma-delta stereo ADC with 128X over-sampling
• Sigma-delta stereo DAC with 128X over-sampling
• On-chip 8X Interpolation Filter
• On-chip analog post filter
• Single-ended input and output
• Sampling rate of 5KHz to 48KHz
The codec serial interface provides a means to read and
write 16-bit stereo data from the ADC or to the DAC respec-
tively. The interface (as shown in Figure 4-1) consists of the
following lines:
• DAC[15:0] - to write to the DAC 16-bit input
• ADC[15:0] - to read the ADC 16-bit output
• L/R - to select between the left and right channels for both
the ADC and DAC data.
• MCLK - This internal master clock signal is synthesized by
the frequency synthesizer from the crystal reference of
14.318MHz. One of 236 frequencies may be selected
through the 8-bit FSEL line. MCLK is not active when the
frequency synthesizer is powered down. The frequency of
MCLK is 256 times the sampling frequency.
The DAC left/right 16-bit input data are multiplexed onto
DAC[15:0] and fed into the codec. The L/R signal qualifies
the data. The period of L/R is equal to that of the codec sam-
pling frequency. One set of left/right 16-bit input data to the
DAC is sent every L/R cycle. When L/R is low, the data on
DAC[15:0] is meant for the left channel; when L/R is high, the
data is meant for the right channel. This means that the DAC
treats data packets L1 and R1 as belonging to the same sam-
pling instance; while L2 and R2 are data for the next sam-
pling instance.
The ADC left/right 16-bit output data are similarly multiplexed
onto the ADC[15:0] bus.
Figure 4-1 Functional Block Diagram
AVCC
AGND
CINR
CINL
Stereo 16-Bit Sigma-Delta ADC
Analog
Sigma-Delta
Modulator
Analog
Sigma-Delta
Modulator
1
128fs
1
128fs
128:1
16
Decimation
Filter
fs
128:1
16
Decimation
Filter
fs
DACL
DACR
VREF
MCLK
Stereo 16-Bit Sigma-Delta DAC
Analog
Low-Pass
Filter
Digital
16
Sigma-Delta
Modulator _8fs
8X
Interpolator
Analog
Low-Pass
Filter
Digital
16
Sigma-Delta
Modulator 8fs
8X
Interpolator
Voltage Reference
Clock Generation
Power Supply
VCC VCC
PD
OPTi
®
Page 20
912-3000-035
Revision: 2.1