Table 12. pll clock frequency detection, 9 clock status (address 08h) (read only) – Cirrus Logic CS42426 User Manual
Page 50
50
DS604F2
CS42426
6.9
Clock Status (address 08h) (Read Only)
6.9.1
SYSTEM CLOCK SELECTION (ACTIVE_CLK)
Default = x
0 - Output of PLL
1 - OMCK
Function:
This bit identifies the source of the internal system clock (MCLK).
6.9.2
PLL CLOCK FREQUENCY (PLL_CLKX)
Default = xxx
Function:
The CS42426 detects the ratio between the OMCK and the recovered clock from the PLL. Given the
absolute frequency of OMCK, this ratio may be used to determine the absolute frequency of the PLL
clock.
If a 12.2880 MHz, 18.4320 MHz, or 24.5760 MHz clock is applied to OMCK and the OMCK_FREQX
bits are set accordingly (see
“OMCK Frequency (OMCK Freqx)” on page 48
), the absolute frequency
of the PLL clock is reflected in the PLL_CLKX bits according to
. If the absolute frequency of
the PLL clock does not match one of the frequencies given in
, these bits will reflect the clos-
est available value.
If the frequency of OMCK is not equal to 12.2880 MHz, 18.4320 MHz, or 24.5760 MHz, the contents
of the PLL_CLKX bits will be inaccurate and should be disregarded. In this case, an external controller
may use the contents of the OMCK/PLL_CLK ratio register and the known OMCK frequency to de-
termine the absolute frequency of the PLL clock.
Note:
These bits are set to ‘111’b when the FRC_PLL_LK bit is ‘1’b.
7
6
5
4
3
2
1
0
Reserved
Reserved
Reserved
Reserved
Active_CLK
PLL_CLK2
PLL_CLK1
PLL_CLK0
PLL_CLK2
PLL_CLK1
PLL_CLK0
Description
0
0
0
8.1920 MHz
0
0
1
11.2896 MHz
0
1
0
12.288 MHz
0
1
1
16.3840 MHz
1
0
0
22.5792 MHz
1
0
1
24.5760 MHz
1
1
0
45.1584 MHz
1
1
1
49.1520 MHz
Table 12. PLL Clock Frequency Detection