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pcm1793 sample rate determination

Tobyn VanVeghten
Intellectual 700 points
Other Parts Discussed in Thread: PCM1793

Greetings,


According to the data sheet for the PCM1793 on page 13, it says the device automatically detects the system clock frequency.  However, when I look at Table 1, 96 kHz sampling frequency at  128 fs has the same system clock frequency (12.288 MHz) as 48 kHz sampling frequency at 256 fs (12.288 MHz).  How does the device differentiate between the two sampling frequencies?  What do I have to do to help it distinguish between the two?  Do I have to maintain a certain relationship between the bit clock (BCK) and the system clock?  Page 15 mentions that the bit clock (BCK) and system clock have to be in sync, but it does specify anything further than that.  By sync, do they need to be at the same frequency, 1/2, ?


Thanks,

Tobyn

  • 0
    TI__Guru**** 189399 points

    Hi, Tobyn,

    My understanding is any of those combinations will be automatically selected and work.

    -d2

  • 0 in reply to Don Dapkus
    Intellectual 700 points

    The datasheet doesn't give any information on the size and length of the data format or the relationship to the system clock.  It says it supports standard data formats, but what is TI's interpretation of these formats?  Are these 32 bit words, where the 2 x word size is framed to equal sample rate?  E.g. at 128 fs of 192 kHz sampling frequency (system clock = 24.576 MHz).  Should BCK be 1/2 of system clock (12.288 MHz), so 64 bits (left + right words) fits evenly and completely into one sampling interval at 192 kHz sampling frequency?  Is this how it figures out the desired sampling frequency?


    Thanks,

    Tobyn