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Original question:

DS90UB933-Q1: Is LINK Detect functionality based on back channel?

DS90UB933-Q1: DS90UB93x link detect funtion

Ted Zhang
Intellectual 2280 points
Part Number: DS90UB933-Q1

HI Team,

My customer is asking how our DS90UB933/4 or 935/936 detect cable link status? I found that only in Serializers we have link detect register, while the DES don't have. This is kinda weird, normally the link detect register should be on the same side as SOC, correct? So if any link down issue happen, the DES can report to SOC the error, right? And if the link down information is only available through register?

Customer mentioned that our competitor the cable link diagnostic is implemented by pure hardware..

Could you please kindly help with the cable link diagnostic logic for our FPDLINK III?

Many thanks

  • 0
    TI__Guru** 103215 points

    Hello Ted,

    For the deserializer side you should monitor the LOCK pin and or LOCK status in the registers to determine if the link has been interrupted.

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Intellectual 2280 points

    HI Casey,

    Thanks for your feedback. 

    However my questions is there are a lot reason that might lead to a lock change, how can you know if it is a cable drop?

    And why we have the cable link diagnostic function in 933, but not 934?

    Thanks

  • 0 in reply to Ted Zhang
    TI__Guru** 103215 points

    Hello Ted,

    Cable fault on the 933 is very similar to 934's LOCK detection and would be used the same way on both sides of the link. The 933 doesn't have any additional knowledge about the cable vs. 934. For example if the 934 is shut down and not outputting anything then the 933 would indicate no cable link detected even if the cable is still connected. The fault registers indicate that between the SER and DES there is no valid link. It doesn't give any specific information about why there is no link.

    Best Regards,

    Casey