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Old 16th October 2012, 12:53 PM   #1
Phisci is offline Phisci  South Africa
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Default Help a newbie understand digital glue

Digital newbie looking for good info:
So I have 11.xxMHz transport, a CS8412 and PCM63 dac and I'd like to create a zero-oversampling dac. The schematic for this is here:
Cs8412 - Pcm63 Non-oversampling

I can solder the thing together and it will probably work, but I'd like to understand how the various bits fit together, how the timings work etc.


Any help would be much appreciated!
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Old 16th October 2012, 02:02 PM   #2
Phisci is offline Phisci  South Africa
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So question 1:
The SPDIF is received by the CS8412, which then generates a clock and data output.
How do you determine what the clock should be for a given DAC?
How do you know if it should be 256*Fs or 384*Fs, where Fs is 44.1kHz?
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Old 16th October 2012, 02:21 PM   #3
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The CS8412 produces a clock at 256*fs, but this isn't required by the PCM63. A clock at 256*fs is typically called 'MCLK' for 'Master Clock' - but older style multibit DACs don't need this clock because they have no digital processing internally that requires such a clock.

PCM63 just needs bit clock, data and a frame sync pulse which indicates the data start.
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Old 16th October 2012, 02:54 PM   #4
Phisci is offline Phisci  South Africa
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Thx abraxalito, when I look at the CS8412 data sheet, it says it can output MCK at 256Fs, SCK at 64Fs, and FS.

But how do you know what the PCM63 needs? Where does it say "I need 256Fs or 384Fs or 64Fs"?
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Old 16th October 2012, 03:40 PM   #5
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Have you pulled up the datasheet for the PCM63? Fig 2 on page 7 shows the timing diagram - the top three traces are the inputs: CLOCK, DATA and LE. Seeing as the CS8412 produces CLK at 64fs, you just need to check that this frequency is acceptable to the PCM63 - page 2 shows the maximum permitted is 25MHz. LE isn't produced by the CS8412 - that's the purpose of the logic in the schematic you linked to.
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Old 16th October 2012, 04:09 PM   #6
Phisci is offline Phisci  South Africa
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So I could feed 64Fs or 256Fs to the PCM63?
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Old 16th October 2012, 04:34 PM   #7
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Technically both are possible though if you sent 256fs to it you'd not like the sound of the noise coming out - the digital data is synchronized to the 64fs clock, not the 256fs one. Consult the CS8412 datasheet.
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