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AD73322L Digital loop-back mode

Question asked by jesortsan on Jan 20, 2017


I need to be able to enable/disable AD73322L digital loop-back mode feature for
diagnostic purposes while the device is running.

The device is configured in mixed mode and is properly working with audio
samples and control words. I am able to change any register value (input gain,
output gain, analog loop-back, mute, etc.) on the run without any issue on any
of the 8 channels present in my design (4 x AD73322L chips). But when I make a
digital loop-back, I have some issues:
* I set SLB bit in control register A to '1' in order to enable the DLM feature
and it works fine. The loop is correctly done.
* The problem comes when I try to get back to normal operation without DLM. I'm
setting SLB bit in control register A to '0' and the loop seems to be disabled,
but the incoming audio to that DAC is not transmitted. I have checked SDI and
SDIFS signals and they are completely correct, audio samples are being properly
sent through SPORT to the AD73322L, but audio is not coming out.

After reading the datasheet several times, my understanding is that I only need
to set SLB bit in control register A to '0' in order to get back to normal
operation, but maybe I'm wrong and some other instruction is needed, or maybe a
reset, I don't know.

I would appreciate your help on this issue, since I don't know how to solve it.

Best regards