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DS90UB914A Question

Kei Sato73562
Expert 2310 points
Other Parts Discussed in Thread: ALP

Is there the Power up sequence of DS90UB914A?

Is there the Power down sequence of DS90UB914A?

What should be written to registers of Reserved.  0? or 1?

 

  • 0
    TI__Genius 14890 points

    Sato-san,


    I believe that this question would be better answered in this forum.

  • 0 in reply to Alexander Scheuermann
    Intellectual 530 points
    Dear support team

    > What should be written to registers of Reserved. 0? or 1?
    My customer has the same upper question.
    Could you answer me?

    Best Regards
    Masaaki Sugiyama
  • 0 in reply to Masaaki Sugiyama
    TI__Expert 5210 points

    Hello,

    As mentioned in datasheet, please DO NOT write to reserved registers. No initialization needs to occur from the customer as these registers are already initialized internally and should not be written to. Some registers have 1 value and others 0 so in order to ensure correct operation of FPD-Link system, please tell your customers not to initialize reserved registers. See page 34 of 914A datasheet for Note (1) which describes this.

    It is also not recommended to initialize registers that are not reserved (public registers). A lot of times, customers will try to initialize public registers and cause issues with the system because they write the wrong value. Public registers SHOULD NOT be initialized, identical to reserved registers.

    The only registers that should be changed are ones that customer explicitly wants to change functionality of from default. The FPD-Link devices are made to start-up with registers initialized to prevent customers from having to perform initialization after power-up over I2C. Thank you.

    -Sean

  • 0 in reply to Sean Thornton1
    Intellectual 530 points

    Dear Sean-san:

    Thank you for your quick reply.

    I understood about reserved register.

    How about reserved bit?

    For example, what should be written to 914A.0x01[7:6]?

    And is all reserved bits the same value?

    Best Regards,

     Masaaki Sugiyama

  • 0 in reply to Masaaki Sugiyama
    TI__Expert 5210 points
    Hello,

    Reserved bits should also NOT be written to. Not all reserved bits are same value; most are certainly 0 but a few are 1.

    I understand that if your microprocessor needs to initialize registers, and it can't initialize bit by bit (through bit masking or another method), what I would recommend is reading the register first during normal system operation (default operation), recording the value of the register (including reserved bits), and then specifically writing the correct values when you initialize the register through I2C communication on your microprocessor.

    Another way to find out default values of reserved register bits is to connect a 913A EVM and a 914A EVM in the lab, make sure that there is stable LOCK and no errors on forward or back channel, and perform register dump over I2C for both 913A and 914A devices using our ALP software (ti.com/tool/ALP). The register dump during normal system operation will give the values of these reserved bits.

    -Sean
  • 0 in reply to Sean Thornton1
    Intellectual 530 points

    Sean-san

    Thank you for your kind support.

    I will replay my customer by the contents mentioned above.

    Best Regards,

     Masaaki Sugiyama