User Manual

46 DS851F2
CS42L56
4.8 Serial Port Clocking
The CODEC serial audio interface port operates either as a slave or master. It accepts externally generated
clocks in Slave Mode (M/S
= 0b) and will generate synchronous clocks derived from an input master clock
(MCLK) in Master Mode (M/S
= 1b). The RATIO[4:0] bits need to be set appropriately according to the
clocks being used in the system for correct device functionality. Table 3. “Serial Port Clock Ratio Settings”
beginning on page 47 shows possible clock frequencies achievable by the CS42L56 serial port and pro-
vides a reference on how the RATIO[4:0] bits need to be configured for different clock ratios. Figure 31
shows how SCLK and LRCK are internally derived in Master Mode.
MCLK (MHz) LRCK (kHz)
MCLK/ LRCK
Clock Ratio
SCLK (MHz)
MCLK/SCLK
Clock Ratio
RATIO[4:0]
22.5792
(MKPREDIV=1b)
(MCLKDIV2=1b)
11.0250 2048 0.7056 32 11000
22.0500 1024 1.4112 16 10000
44.1000 512 2.8224 8 01000
11.2896
(MKPREDIV=0b)
(MCLKDIV2=1b)
11.0250 1024 0.7056 16 11000
22.0500 512 1.4112 8 10000
44.1000 256 2.8224 4 01000
5.6448
(MKPREDIV=0b)
(MCLKDIV2=0b)
11.0250 512 0.7056 8 11000
22.0500 256 1.4112 4 10000
44.1000 128 2.8224 2 01000
Table 3. Serial Port Clock Ratio Settings
MAX[2:0]
Output
(after Limiter)
Input
RRATE[5:0]ARATE[5:0]
Volume
Limiter
CUSH[2:0]
ATTACK/RELEASE SOUND
CUSHION
MAX[2:0]
Figure 30. Peak Detect & Limiter