ZHCSAC2C August 2012 – October 2018 PCM5121 , PCM5122
PRODUCTION DATA.
In Master Mode, the device generates bit clock (BCK) and left-right clock (LRCK) and outputs them on the appropriate pins. To configure the device in this mode, first put the device into reset, then use registers BCKO and LRKO (Pg 0, Reg 9 0x09). Then reset the LRCK and BCK divider counters using bits RBCK and RLRK (Pg 0, Reg 12 0x0C). Finally, exit reset.
An example of this is given in register programming examples in the PCM5242 data sheet (SLASE12.)
Figure 64 shows a simplified serial port clock tree for the device in master mode.
In master mode, SCK is an input and BCK/LRCK are outputs. BCK and LRCK are integer divisions of SCK. Master mode with a non-audio rate master clock source will require external GPIOs to use the PLL in standalone mode.
The PLL will also need to be configured to ensure that the onchip audio processor processor can be driven at its maximum clock rate.
Register changes that need to be done include switching the device into master mode, and setting the divider ratio.
Here is an example of using 24.576 MCLK as a master clock source and driving the BCK and LRCK with integer dividers to create 48 kHz.
In this mode, the DAC section of the device is also running from the PLL output. While the PLL inside the PCM512x is one that has been specified to achieve the stated performance, using the SCK CMOS Oscillator source will have less jitter.
To switch the DAC clocks (SDAC in the Figure 63) the following registers should be modified.
An example configuration can be found in the PCM5242 data sheet (SLASE12).