Table 11. master clock source select, 8 omck/pll_clk ratio (address 07h) (read only) – Cirrus Logic CS42428 User Manual
Page 49
DS605F2
49
CS42428
6.7.4
MASTER CLOCK SOURCE SELECT (SW_CTRLX)
Default = 00
Function:
These two bits, along with the UNLOCK bit in register
“Interrupt Status (address 20h) (Read Only)”
, determine the master clock source for the CS42428. When SW_CTRL1 and SW_CTRL0
are set to '00'b, selecting the output of the PLL as the internal clock source, and the PLL becomes
unlocked, RMCK will equal OMCK, but all internal and serial port timings are not valid.
When the FRC_PLL_LK bit is set to ‘1’b, the SW_CTRLX bits must be set to ‘00’b. If the PLL becomes
unlocked when the FRC_PLL_LK bit is set to ‘1’b, RMCK will not equal OMCK.
6.7.5
FORCE PLL LOCK (FRC_PLL_LK)
Default = 0
Function:
This bit is used to enable the PLL to lock to the ADC_LRCK with the absence of a clock signal on
OMCK. When set to a ‘1’b, the auto-detect sample frequency feature will be disabled and the SW_C-
TRLX bits must be set to ‘00’b. The OMCK/PLL_CLK Ratio (address 07h) (Read Only) register con-
tents are not valid, and the PLL_CLK[2:0] bits will be set to ‘111’b. Use the DE-EMPH[1:0] bits to
properly apply de-emphasis filtering.
6.8
OMCK/PLL_CLK Ratio (address 07h) (Read Only)
6.8.1
OMCK/PLL_CLK RATIO (RATIOX)
Default = xxxxxxxx
Function:
This register allows the user to find the exact absolute frequency of the recovered MCLK coming from
the PLL. This value is represented as an integer (RATIO7:6) and a fractional (RATIO5:0) part. For
example, an OMCK/PLL_CLK ratio of 1.5 would be displayed as 60h.
SW_CTRL1 SW_CTRL0 UNLOCK
Description
0
0
X
Manual setting, MCLK sourced from PLL.
0
1
X
Manual setting, MCLK sourced from OMCK.
1
0
0
1
Hold, keep same MCLK source.Auto switch, MCLK
sourced from OMCK.
1
1
0
1
Auto switch, MCLK sourced from PLL.
Auto switch, MCLK sourced from OMCK.
Table 11. Master Clock Source Select
7
6
5
4
3
2
1
0
RATIO7(2
1
)
RATIO6(2
0
)
RATIO5(2
-1
)
RATIO4(2
-2
)
RATIO3(2
-3
)
RATIO2(2
-4
)
RATIO1(2
-5
)
RATIO0(2
-6
)