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PCM1865 8ch TDM transmissiondata

kyt
Expert 2355 points
Other Parts Discussed in Thread: PCM1865, PCM1808, PCM4204

In D/S as below section,it is semme that PCM1865 does not support 8ch(4ch/L+R) TDM.

supports only 2ch,4ch,6ch TDM.

Page 0 / Register 12 (Hex 0x0C),TDM_OSEL[1:0]

http://www.ti.com/lit/ds/symlink/pcm1865.pdf

So, can PCM1865  be support 8ch TDM datastream?

best regards,

kyt

  • 0
    TI__Mastermind 27920 points

    Hi Kyt,

    The PCM1865 must have BCK at 256*fs when running in TDM mode. This means there are 8 32-bit channels available on the data line. The register you are referring to in your post allows you to choose if you want this part to use 2, 4 or 6 of those 8 available channels. Then the remaining channels can be used by another device.

    Justin

  • 0 in reply to Justin Bohr
    Expert 2355 points

    Hi Justin,

    Thank you for your reply.

    You mentioned that it can be connect for  Two PCM1808 devices like PCM4204 using as below D/S Fig.7?

    http://www.ti.com/lit/ds/symlink/pcm4204.pdf

    I'd like to make 8ch/TDMcompose by one device.

    Is such composition possible by TI product portfolio?

    best regards,

    kyt

  • 0 in reply to kyt
    TI__Mastermind 27920 points

    Hi Kyt,

    Yes you could use two PCM1865 (both in 4 channel TDM mode) or 4 PCM186X (1 or 3 in 2 channel TDM mode) and get 8 channel TDM just as the PCM4204 is showing in figure 7. You would set to TDM mode, and then with the right TDM offset settings you can have an single 8 channel TDM signal to go to a DSP.

    The PCM1808 does not have a TDM mode. We also do not have an 8 channel Audio ADC in our portfolio.

    Justin

  • 0 in reply to Justin Bohr
    TI__Intellectual 2155 points

    Justin,

    You state that you can run 2x PCM1865 on an 8-Ch TDM stream. My question for you is what happens to the DOUT line (Assuming both PCM are driving the same DOUT line) when it is not driving. Does it go into high impedance?

  • 0 in reply to Scott McElroy1
    TI__Mastermind 27920 points
    Hi Scott,

    I have just tested the TDM mode both in master and in slave. In both modes when not outputting a word, the lines will be left in High Z so that another device on the bus can drive the line.

    One thing to note is that in master mode the pulse function cannot be used. The LRCK will have to be a 50% duty cycle, but because TDM only cares about the rising edge for the frame sync this should not be a problem.

    Justin