Cirrus Logic CS4202 - Manual (Page 42)

CS4202
42 DS549PP2
5. SERIAL DATA PORTS
5.1 Overview
The CS4202 implements two serial data output
ports that can be used for multi-channel expansion.
Each serial port consists of 4 signals: MCLK,
SCLK, LRCLK, and SDATA. The existing 256 Fs
BIT_CLK will be used as MCLK. The clock pins
are shared between all the serial ports with only the
SDATA pins being separate; SDOUT for the first
output port, and SDO2 for the second output port.
Serial data is transmitted on these ports every
AC-link frame.
The serial data port is controlled by the SDEN,
SDSC, and SDO2 bits in the Serial Port Control
Register (Index 6Ah). All the serial data port pins
are multiplexed with other functions and cannot be
used unless the other function is disabled or pow-
ered down; see Section 7, Exclusive Functions.
Some audio DACs can run in an internal SCLK
mode where SCLK is internally derived from
MCLK and LRCLK. In this case, SCLK generation
in the CS4202 is optional.
A feature has been designed into the CS4202 that
allows the phase of the internal DACs to be re-
versed. This DAC phase reversal is controlled by
the DPC bit in the Misc. Crystal Control Register
(Index 60h). This feature is necessary since the
phase response for external DACs is unknown and
the phase response of the internal DACs can vary
depending on the path determined by the DDM bit
in the AC Mode Control Register (Index 5Eh) and
the output (LINE_OUT or HP_OUT) being used.
This feature guarantees that all DACs in a system
have the same phase response, maintaining the ac-
curacy of spatial cues.
Please note the data sent to the serial ports is
straight from the AC-link. There is no SRC and no
volume control available on this data, so it is the re-
sponsibility of the controller or host software to
provide this functionality if desired.
5.2 Multi-Channel Expansion
For multi-channel expansion, the two serial data
output ports are used to send AC-link data to one or
two external stereo DACs to support up to a total of
six channels. The first serial port takes the digital
audio data from the SDOUT slots. The second seri-
al port takes the digital audio data from the SDO2
slots. See Table 8 on page 30 for the actual slots
used depending on configuration. Figure 10 shows
a six channel application using the CS4202.
8
5 4
3
2
1
4
3
2
1 8
5
AOUTL
AOUTR
SDATA
DEM#/SCLK
LRCK
MCLK
GPIO1/SDOUT
GPIO4/SDO2
44
34
47
43
EAPD/SCLK
GPIO0/LRCLK
LINE_OUT_L
LINE_OUT_R
BIT_CLK
6
36
35
CS4334
AOUTL
AOUTR
SDATA
DEM#/SCLK
LRCK
MCLK
CS4334
270K 270K
10uF
ELEC
10uF
ELEC
47K 47K
560
560
2700pF 2700pF
Left Surround
Right Surround
270K 270K
10uF
ELEC
10uF
ELEC
47K 47K
560
560
2700pF 2700pF
Center
LFE
AGND AGND
AGND AGND
Left Front
Right Front
AGND
AGND
10uF
ELEC
10uF
ELEC
1000pF
AGND
220K 220K
AGND
1000pF
+
+
+
+
+
+
Figure 10. Serial Data Port: Six Channel Circuit