Slave to TDM Clock Domain
I want to bring in a TDM8 clock domain (BCLK and LRCLK) to domain 2 (for example) on the ADAU1442 Sigma DSP. I then want to set the Start Pulse Select value to "fs from serial input pair 2" so that the core is synchronized to this domain. Finally, I want to set other clock domains as Master, Enabled Outputs to drive other audio devices.
First Question: I'm counting on the Output Master domains so created being synchronous to the input TDM8 clock domain on 2 since I have set the start pulse select to the "fs from serial input pair 2". Could an ADI person please confirm?
Second Question: I don't anticipate having any audio data on serial input 2. I simply want to use clock domain 2 as a frame sync to the core. Do I still have to set the "Serial Input 2" TDM Type to "TDM8 or Flexible TDM Mode" for the start pulse selection to work? If I have to set the unused serial to TDM8 then I'll end up using 8 channels of automatic channel assignment. If I can leave the serial selection at "TDM2 Stereo" and not use the serial port for data, then I would hope to keep the automatic channel assignment count at 2 for Serial input 2.
Thanks
Audio Signal Processors
adau1442
processors and dsp
SigmaDSP Audio Processors
Processors and Microcontrollers
Hi Dave,
First Question Answer:
Both devices are on asynchronous clock domains (START Pulse = "Fs from serial input Stereo Pair 2", and Output Master Domains set to "internally generated normal rate fsNORMAL"). The Output Master domains could be made synchronous to the input (slave) TDM8 clock domain is if both devices derived their clocks from the same Master Clock source.
Second Question Answer:
In order for the LRCLK2 to be seen as a START PULSE for the core, the serial port has to be enabled. Since it is used, the automatic channel assignment would use a minimum of 2 channels. Even if the LRCLK2 is generated from a TDM8 bus (i.e. 12.288 MHz BLCK, 48 kHZ LRCLK, 8 x 32-bit channels), you can still set the serial port input to TDM2 to save on channel assignments and just ignore (no-connect) the input serial data.
Regards,
-John
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