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DS90UB927Q-Q1: 927-940, link detect status is 0 not detected, but the screen picture is normal

Iris Shen
Expert 4002 points
Part Number: DS90UB927Q-Q1

Hi team,

My customer use 927 with 940, they found the 927 0x0C register bit 0 is 0, cable link not detected, but the screen picture seems to be normal. They want to know the cause. 

The 927 register dump is shown as below, they can't get access to 940 I2C address:

  • 0
    TI__Guru 66840 points

    Hi Iris, 

    Link detect from 927 is representative of an operational back-channel. In this case, if Foward-channel video data is still operational; then this might indicate an issue with the back channel operation. This seems potentially the case here considering the DES Error indicated also in 0xC register. 

    What is getting reported from 940 side? Is there lock? 

    Customer isn't actually doing local 940 PG by mistake?

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    TI__Expert 4002 points

    Hi Logan,

    Customer tested the lock pin status of 940 and said it is always high. They double checked the local pattern generation and they didn't use. Do you have some idea? Thanks!

  • 0 in reply to Iris Shen
    TI__Guru 66840 points

    Hi Iris, 

    Thanks for the follow-up. 

    Can you provide their schematic as well? I'd like to double check their configuration, AC cap values, etc. 

    Is this able to be replicated at all? Was this on bench or vehicle? 

    There might be a couple other tests we can try as well if possible.

    Regards, 

    Logan