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DS90UB954-Q1: DS90UB954 register error

Sammi Shang
Expert 4450 points
Part Number: DS90UB954-Q1


Dear team,

Customer used 901+954 in their project as serDes and equalizer. When they read the register of 954 through I2C, all register displays 0xFF. But customer has never written the register and the default of the register is also not oxFF. So customer want to know if they missed any important configuration?

Thanks.

Best regards,

Sammi

  • 0
    TI__Mastermind 18755 points

    Hi Sammi,

    To clarify they get a response from the 954 and all registers read 0xff?  Are you able to probe the I2C lines to see if you are getting a valid signal?  It sounds like the device is not properly pulling the I2C lines to ground?

    Regards,

    Nick

  • 0 in reply to Nicholas Darash
    TI__Expert 4450 points

    Hi Nick,

    Customer tried around 5 registers by oscilloscope directly, and each of them showed a value of 0xff with standard I2C timing chart. And they pull the I2C lines to 1.8V through a 10k-ohm register. So what does 'pulling the I2C lines to ground' mean?

    Customer also have below questions:

    1. One board, I2C pull up, when set PDB of 945 to high through software, all I2C level change to 0.

    2. One board, when set PDB of 945 to high through software, 954 could connect with MCU through I2C, but all register read 0xff.

    3. If MCU want to connect with 913 with I2C, should set 954 registers first?

    Thanks.

    Best regards,

    Sammi

  • 0 in reply to Sammi Shang
    TI__Mastermind 18755 points

    Hello Sammi,

    First I would say a typical pull-up value is between 470 and 4.7k Ohms.  10k may be too weak for the signal to work properly.  Also the 'pull to ground' quote was just bad wording on my part.  I meant that the communication is not working properly.

    1.) Are you communicating with the serializer separately?

    2.) Are you able to verify with the probe that you are getting ACKs and is the MCU you are using able to support clock stretching?

    3.) You will need to update register 0x58 backchannel speed for the serializer

    Regards,

    Nick