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DS90UB638-Q1: We would like to understand DS90UB638-Q1 CRC error relative Pass pin relationship behavior

Roy Chan
Expert 4840 points

Part Number: DS90UB638-Q1
Other Parts Discussed in Thread: DS90UB635-Q1

Tool/software:

Hello Expert :

   We checked DS90UB638-Q1 PASS pin H or L  have relative CRC error in BIST mode. 

base on the datasheet description , I  would like double check for Forward channel video data line transmission , if there have an one  CRC error triggered  , the PASS pin always = High ,

If there have an one CRC error triggered in back channel BIST the pass pin will always will pull low, am I correct? 

another questions is if device get one CRC error founded , that means we might need to check the HW SI quality have any issues , am I correct? 

I'm appreciate if you can give me more information regarding CRC error basic on DS90UB635-Q1 and 638 . 

thank you

Roy

  • +1
    TI__Mastermind 28750 points

    Hello,

    The deserializer is monitoring for forward channel errors when in BIST mode. If there is a error on the forward channel, when operating in BIST mode, the PASS signal will go LOW. You can monitor the total BIST error count using register 0x57. 

    The number of acceptable BIST errors is dependent on the length of time BIST is run and the system requirements. The amount of time that BIST mode is run without any errors can be used to determine the BER level of the system. The acceptable BER level will depend on the system requirements. More details on calculating BER and BIST timings can be found here. However, you are correct if there are a significant number of errors, the hardware and signal integrity of the system should be investigated. Please note that BIST mode is not a mission mode diagnostic, and other errors or operations not related to the FPD-Link channel are not active.