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Disparity error checking in TLK1501?

1243558
Prodigy 190 points
Other Parts Discussed in Thread: TLK1501, TLK3134

Does the TLK1501 receiver check running disparity of the incoming serial signal?  There appears to be no comment on this in the datasheet.  Similar parts, like the TLK3134, report an error on the output bus if the disparity is not correct.  Is this also true of the TLK1501, or does it ignore disparity on the input signal?  If disparity is checked, how is the status reported?

  • 0
    TI__Mastermind 20820 points

    Hi,

    The TLK1501 uses 8B/10B encoding/decoding to transmit data to ensure DC balanced signalling. It also uses this to do the error checking. Pages 11-13 of the data sheet, synchronization and initialization, explains this in detail.

    Regards,

    Mike

  • 0
    TI__Mastermind 20820 points

    Hi,

    Checked with the design team on this and the TLK1501 uses both running disparity and a look up table to do the error checking.

    Regards,

    Mike

  • 0 in reply to Michael Peffers
    Prodigy 190 points

    Hi Michael,

    Thanks for the response.  I'd like to know if the TLK1501 detects a disparity error, how does it signal the error detection?  We have a significant amount of data acquired from the output of the 1501, and most of the time the data (a ramp test pattern generated by our source device) is numerically correct, but an error is indicated (that is, both the RX_DV and RX_ER pins are high).  If the data is correct, why is the RX_ER pin high?  I'm suspicious that our source device may not be generating disparity correctly, and that the 1501 is signaling a received disparity error, so that's why I'm trying to get a better description of how the 1501 signals a detected disparity error.

    If a disparity error is not signaled by asserting RX_ER, is there any other reason the 1501 would be asserting an error indicator on data that is verifiably correct?

  • 0 in reply to 1243558
    TI__Mastermind 20820 points

    Hi,

    Thank you for the additional information, it helped me understand your problem better.

    The TLK1501 signals an error through the RX_DV/LOS and RX_ER pins. The section "comma detect and 8-bit/10-bit decoding" and table 2 on page of 11 of the data sheet gives a good description of the meaning of each state that the RX_DV/LOS and RX_ER can be in on TLK1501.

    The TLK1501s decoder block is simply going to decode whatever data that is feed into it so a disparity error would be coming from your source. I would check the source that is generating the data and make sure that the disparity is correct when it is transmitted. Please let me know if you have any more questions.

    Regards,

    Mike