CS42516
26
DS583PP5
4.5.2
OMCK System Clock Mode
A special clock switching mode is available that allows the clock that is input through the OMCK pin to be
used as the internal master clock. This feature is controlled by the SW_CTRLx bits in register “Clock Con-
trol (address 06h)” on page 52. An advanced auto switching mode is also implemented to maintain master
clock functionality. The clock auto switching mode allows the clock input through OMCK to be used as a
clock in the system without any disruption when the PLL loses lock; for example, when the input is re-
moved from the receiver. This clock switching is done glitch free. A clock adhering to the specifications
detailed in the Switching Characteristics table on page 12 must be applied to the OMCK pin at all times
that the FRC_PLL_LK bit is set to ‘0’ (See “Force PLL Lock (FRC_PLL_LK)” on page 53).
4.5.3
Master Mode
In master mode, the serial interface timings are derived from an external clock attached to OMCK or the
output of the PLL with an input reference to either the S/PDIF Receiver recovered clock or the SAI_LRCK
input from the Serial Audio Interface Port. Master clock selection and operation is configured with the
SW_CTRL1:0 bits in the Clock Control Register (See “Clock Control (address 06h)” on page 52).
The supported PLL output frequencies are shown in Table 2 below.
4.5.4
Slave Mode
In Slave mode, CX_LRCK, CX_SCLK and/or SAI_LRCK, SAI_SCLK operate as inputs. The Left/Right
clock signal must be equal to the sample rate, Fs, and must be synchronously derived from the supplied
master clock, OMCK or the output of the PLL. The serial bit clock, CX_SCLK and/or SAI_SCLK, must be
synchronously derived from the master clock and be equal to 128x, 64x, 48x or 32x Fs depending on the
interface format selected and desired speed mode. One Line Mode #1 is supported in Slave Mode. One
Line Mode #2 is not supported. Refer to Table 3 for required clock ratios. The sample rate to OMCK ratios
and OMCK frequency requirements for Slave mode operation are shown in Table 1.
Single Speed
Double Speed
Quad Speed
One Line Mode #1
OMCK/LRCK Ratio
256x, 384x, 512x
128x, 192x, 256x
64x, 96x, 128x
256x
Table 3. Slave Mode Clock Ratios
Sample
Rate
(kHz)
OMCK (MHz)
Single Speed
(4 to 50 kHz)
Double Speed
(50 to 100 kHz)
Quad Speed
(100 to 192 kHz)
256x
384x
512x
128x
192x
256x
64x
96x
128x
48
12.2880 18.4320 24.5760
-
-
-
-
-
-
96
-
-
-
12.2880 18.4320 24.5760
-
-
-
192
-
-
-
-
-
-
12.2880 18.4320 24.5760
Table 1. Common OMCK Clock Frequencies
Sample
Rate
(kHz)
PLL Output (MHz)
Single Speed
(4 to 50 kHz)
Double Speed
(50 to 100 kHz)
Quad Speed
(100 to 192 kHz)
256x
256x
256x
32
8.1920
-
-
44.1
11.2896
-
-
48
12.2880
-
-
64
-
16.3840
-
88.2
-
22.5792
-
96
-
24.5760
-
176.4
-
-
45.1584
192
-
-
49.1520
Table 2. Common PLL Output Clock Frequencies