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DS90UH940N-Q1: Questions for 940N BIST

Harry Shin1
Expert 6000 points
Part Number: DS90UH940N-Q1

Hello Team,

My customer has several question for 940N BIST option.

Could you pls help answer it??

1) For BISTC, this is for clock selection for BIST, if BISTC is enabled, internal CLK 33MHz will be used.

if so, FC rate would be 33MHz*35bit=1.155Gbps??

2) Can 940N support BIST mode with dual ink with BISTC=high? if so, FC rate for port0 and port1 will have 1.155Gbps repectively or each port will output half of 1.155Gbps??

3) For BIST sequence, there is no requirement for bist with power on sequence. So my customer will enable BIST by resistor. then 940N device will start with BIST mode once power on. Is this no problem??

Or 940N should be enter normal mode first before enabled by bist pin??

Thank you.

  • 0
    TI__Mastermind 22520 points

    Hey Harry,

    Harry Shin1 said:

    1) For BISTC, this is for clock selection for BIST, if BISTC is enabled, internal CLK 33MHz will be used.

    if so, FC rate would be 33MHz*35bit=1.155Gbps??

    Yes, that's correct. 

    Harry Shin1 said:
    2) Can 940N support BIST mode with dual ink with BISTC=high? if so, FC rate for port0 and port1 will have 1.155Gbps repectively or each port will output half of 1.155Gbps??

    In dual FPD mode, the PCLK rate is split between the 2 lanes.

    Harry Shin1 said:

    3) For BIST sequence, there is no requirement for bist with power on sequence. So my customer will enable BIST by resistor. then 940N device will start with BIST mode once power on. Is this no problem??

    Or 940N should be enter normal mode first before enabled by bist pin??

    You need to run BIST once both Ser and Des have fully been powered up and are stable. Also, it's best to clear the CRC registers prior to testing to make sure you don't have CRC error residual from power-up.

    Regards,
    Fadi A.

  • 0 in reply to Fadi Abdulhameed
    TI__Expert 6000 points

    Hello Fadi,

    Thanks for your answer. but I am still not clear about this.

    Fadi Abdulhameed said:
    You need to run BIST once both Ser and Des have fully been powered up and are stable. Also, it's best to clear the CRC registers prior to testing to make sure you don't have CRC error residual from power-up.

    Do you mean that Ser-Des should be linked in normal mode first and customer can enable BIST??

    Of course, they will use clear CRC as you recommended.

    Thank you.

  • 0 in reply to Harry Shin1
    TI__Mastermind 22520 points

    Hi Harry,

    Yes power-up the Ser and the Des. Make sure you have link between Ser and Des. Then clear CRC errors, and then run BIST test. 

    Regards,
    Fadi A.