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DS90UB948-Q1: ds90ub947-q1, ds90ub948-q1: LOCK and PASS pins

Le Dinh Anh Quan
Prodigy 50 points
Part Number: DS90UB948-Q1
Other Parts Discussed in Thread: DS90UB947-Q1

Hello, I am having a project about ds90ub947q1 and ds90ub948q1. I am reading ds90ub948-q1.pdf and ds90ub948-q1.pdf and I am having questions about 2 pins LOCK and PASS on ds90ub948q1 chip. I read about them at section about BIST but I can not still understand about function of these 2 pins clearly. I hope that there is any people can explain for me about function of these 2 pins. Except for using in BIST function, are there functions these 2 pins used for? I will be very happy if I receive your helping

  • 0
    TI__Mastermind 18046 points

    Hello, 

    Independent of BIST, the LOCK and PASS pins are status pins during normal operation. 

    LOCK - confirms that the 948 Deserializer has locked to the incoming serial stream from the 947 serializer. This pin will allow the user to know the SER-DES link has been brought up correctly while the BIST function can help troubleshoot the link between the SER and the DES. 

    PASS - Errors from the recovered serial stream are reported to the PASS pin in addition to being reported on the status registers of the devices. 

    I hope this helps. 

    Best,

    Shu

  • 0 in reply to Shu Huang
    Prodigy 50 points

    Thanks your support! After receiving your support, I understood a part. But I want to confirm again. I find in ds90ub948-q1.pdf bit BIST_EN (like picture below), so I want ask that if I enable this bit, PASS pin and LOCK pin will operate in BIST mode. Otherwise, if bit BIST_EN is disabled, LOCK pin and PASS pin will operate in normal mode. Is that right? In Pin Functions table of ds90ub948-q1.pdf, I can't see the description for function of PASS pin in normal mode (like the first picture you used to answer me). Is there any difference?

  • 0 in reply to Le Dinh Anh Quan
    TI__Mastermind 18046 points

    Hi, 

    Apologies, looks like my reference was an older revision of the UB948 datasheet. Looking at the latest revision, the PASS pin ONLY reflects BIST mode operation.  

    Best,

    Shu

  • 0 in reply to Shu Huang
    Prodigy 50 points

    So, if I don't enable bit BIST_EN (register 0x24 bit 0), I can't use any function of PASS pin. Right?

  • 0 in reply to Le Dinh Anh Quan
    TI__Mastermind 18046 points

    Hello, 

    This is correct. PASS status will not be valid when BIST is not enabled. 

    Best,

    Shu

  • 0 in reply to Shu Huang
    Prodigy 50 points

    Hi,

    I read file ds90ub947-q1.pdf and see BIST CRC Error Port0/Port1 bit (like image below). If I connect ds90ub947-q1 with ds90ub948-q1, this bit and PASS pin of ds90ub948-q1 are same function? If not, what's difference in function of BIST CRC Error Port0/Port1 bit and PASS pin?

     

    Hope receive your help soon!

  • 0 in reply to Le Dinh Anh Quan
    TI__Mastermind 18046 points

    Hello, 

    The 947 serializer and 948 deserializer pair uses a bidirectional control channel for high speed Ser to Des forward channel data transfer and lower speed Des to Ser reverse/back channel signaling. 

    The PASS status in BIST indicates errors detected from the forward channel serial data from the 947 to 948. 

    The CRC Errors in BIST will indicate errors detected from the 948 to the 947 sent on the reverse/back channel

    Best,

    Shu

  • 0 in reply to Shu Huang
    Prodigy 50 points

    Okay, thank you so much!!!