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cascading 2 1445 dsps

Question asked by chuckwin on Oct 21, 2014
Latest reply on Nov 6, 2014 by chuckwin



My application requires daisy-chaining two ADA1445 dsps. I'm using 4 ADAU1974 ADCs for input, and a single ADAU1966 DAC for output.


I am connecting the serial data outs from the ADCs straight into dsp1, then out of dsp1 directly into the same-numbered serial inputs of dsp2. Then the same-numbered serial outs from dsp2 go directly into the DAC. All are operating at 24-bit, 48k off the same buffered 12.288MHz master clock.. nothing fancy.


Building off a previous design with a single dsp, I am slaving the 1445's off the ADCs and DAC. Clock domains are all connected from each codec to it's own domain, and the domains are connected to both dsps.


My questions concerns clock domain assignments. For the dsp1 inputs, I'm using domains 3, 4, 6, 7; for the dsp2 outputs I'm using domain 5. Simple enough. But now I'm wondering how best to assign clock domains to the output of dsp1 and the input of dsp 2.


Is there any reason I can't assign CD5 to the output of dsp1 and dsp2 at the same time, while also assigning 3,4,6,7 to the inputs of dsp2? Seems to me since all clocks ultimately originate from the same source, there should be no issues. But I seem to be having some problems getting audio to pass on some channels.


Please advise on best clock domain assignment strategy for this application. Or, perhaps better in this case to use one dsp as master, and slave codecs and second dsp?


any help appreciated in advance.