Cirrus Logic CS42518 - Manual (Page 55)

DS584F2 55
CS42518
6.9.4 RECEIVER CLOCK FREQUENCY (RCVR_CLKX)
Default = xxx
Function:
The CS42518 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 52 ), the absolute frequency
of the PLL clock is reflected in the RCVR_CLKX bits according to Table 16 . If the absolute frequency
of the PLL clock does not match one of the frequencies given in Table 16 , these bits will reflect the
closest 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 RCVR_CLKX bits will be inaccurate and should be disregarded. In this case, an external con-
troller may use the contents of the OMCK/PLL_CLK ratio register and the known OMCK frequency to
determine the absolute frequency of the PLL clock.
Note: These bits are set to ‘111’b when the FRC_PLL_LK bit is ‘1’b.
6.10 Burst Preamble PC and PD Bytes (addresses 09h - 0Ch)(Read Only)
6.10.1 BURST PREAMBLE BITS (PCX & PDX)
Default = xxh
Function:
The PC and PD burst preamble bytes are loaded into these four registers.
RCVR_CLK2 RCVR_CLK1 RCVR_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 14. Receiver Clock Frequency Detection
7 6 5 4 3 2 1 0
PCx-7 PCx-6 PCx-5 PCx-4 PCx-3 PCx-2 PCx-1 PCx-0
PDx-7 PDx-6 PDx-5 PDx-4 PDx-3 PDx-2 PDx-1 PDx-0