Cirrus Logic CS4205 - Manual (Page 55)

CS4205
DS489PP4 55
6.3 Digital Docking
The CS4205 features three serial data input ports
used to receive data from three stereo ADCs inside
a docking station. One serial data output port is
used to transmit data to a stereo DAC inside the
docking station. To fully utilize digital docking, the
CS4205 should be configured for digital centric
mode; see Section 3.2, Digital Centric Mode. This
will allow the docking sources to be mixed with the
analog sources from the notebook. The resulting
mix is available for listening on both the notebook
and the docking station and for capturing on the
host. Figure 16 shows a block diagram for digital
docking applications of the CS4205.
Note the BIT_CLK output should be buffered be-
fore sending it as MCLK to the docking station
converters. The capacitance loading of the docking
station connector, the relatively long trace, and the
multiple loads on this signal may exceed the load-
ing restrictions on BIT_CLK. Buffering of SCLK
and LRCLK should also be considered.
6.4 Serial Data Formats
In order to support a wide variety of serial audio
DACs and ADCs, the CS4205 can transmit and re-
ceive serial data in four different formats. The de-
sired format is selected through the SDF[1:0] bits in
the Serial Port Control Register (Index 6Ah). All se-
rial ports use the same serial data format when en-
abled. In all cases, LRCLK will be synchronous
with Fs, and SCLK will be 64 Fs (BIT_CLK/4). Se-
rial data is transitioned by the CS4205 on the falling
edge of SCLK and latched by the DACs on the next
rising edge. Serial data is shifted out MSB first in all
supported formats, but LRCLK polarity as well as
data justification, alignment, and resolution vary.
Table 23 shows the principal characteristics of each
serial format.
Stereo DAC
Stereo ADC
SCLK
CS4205
Line Out L
Line Out R
Mic In L
Mic In R
LRCLK
SDOUT
SDI1
SDI2
SDI3
Stereo ADC
Line In L
Line In R
Stereo ADC
CD In L
CD In R
BIT_CLK
SDATA_IN
SDATA_OUT
SYNC
RESET#
MCLK
DC '97
Controller
Notebook Side Docking Station Side
Figure 16. Digital Docking Connection Diagram