Cirrus Logic CDB8422 - Manual (Page 25)

DS692DB2 25
CDB8422
3.3 Hardware Mode Control
This section provides a full description for the hardware mode control switches S3, S4, and S7, see the ta-
bles below. Switches S3 and S4 control the pull-up or pull-down resistor value attached to the MS_SEL and
SAOF pins of the CS8422, respectively. Each resistor value is sensed during the power-up sequence to
configure the device correctly. Consequently, for a modification to S3 or S4 to take affect, the CDB8422
should be reset by pressing push-button S5. For all switch positions, 0 = OPEN and 1 = CLOSED. See the
CS8422 data sheet for complete details of hardware mode behavior.
Due to a limited number of switches, the following CS8422 hardware mode configuration settings are not
changeable on the CDB8422: de-emphasis auto-detect is always enabled and the SRC MCLK is always the
PLL clock.
Also, some FPGA register settings are fixed in hardware mode. The MCLK sent to the SAO2 header J25 is
always the CS8422’s RMCK, the TDM subclocks at header J30 are always from SAO1, and the CS8406’s
V, U, C, TCBL, and AUDIO pins are always low.
Switch S3 controls the master/slave and clock ratio options for both serial output ports, see Table 3 for
switch configurations. For SDOUT1, when the serial port is set to master mode, the master clock ratio de-
termines what the output sample rate will be based on the MCLK selected for SDOUT1 (chosen by
position 6 on S7). For SDOUT2, the output sample rate is equal to the sample rate of the incoming receiver
data, and the master mode clock ratio determines the frequency of RMCK relative to the incoming receiver
sample rate.
Note: If SDOUT1 is set to slave mode, the SAO1 header J24 will be the master (not the CS8406) and the
CS8406’s OMCK/ILRCK ratio will be set to 256xFs.
Note: If TDM Mode is selected for SDOUT1 by switch S4, then SDOUT1 cannot be set to “Master Mode,
Fso = MCLK/128”
MS_SEL[3:0] SDOUT1 SDOUT2
0000 Slave Mode
Slave Mode,
RMCK = 256*Fsi
0001 Master Mode, Fso = MCLK/128
0010 Master Mode, Fso = MCLK/256
0011 Master Mode, Fso = MCLK/512
0100 Slave Mode
Master Mode,
RMCK = 128*Fsi
0101 Master Mode, Fso = MCLK/128
0110 Master Mode, Fso = MCLK/256
0111 Master Mode, Fso = MCLK/512
1000 Slave Mode
Master Mode,
RMCK = 256*Fsi
1001 Master Mode, Fso = MCLK/128
1010 Master Mode, Fso = MCLK/256
1011 Master Mode, Fso = MCLK/512
1100 Slave Mode
Master Mode,
RMCK = 512*Fsi
1101 Master Mode, Fso = MCLK/128
1110 Master Mode, Fso = MCLK/256
1111 Master Mode, Fso = MCLK/512
Table 3. S3 Settings