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TUSB542: RX_AP polarity

Takashi Yamaguchi
Genius 13300 points
Part Number: TUSB542

Hi team,

My customer is considering to use the TUSB542. Could you support the question below?

Does this IC distinguish between + and - as internal operations?  For example, is it ok to connect as follows?

- Connect RX_AP+ and other IC USB3SSRX-

- Connect RX_AP- and other IC USB３SSRX+

If this connection is ok, is it necessary to input the RX_Con + / RX_Con- connection with the polarity reversed?

Regards,

Yamaguchi

  • 0
    TI__Guru**** 177071 points

    Yamaguchi

    Lane polarity inversion is covered in section 6.4.2 of the USB 3.1 specification. So TUSB542 supports lane polarity at both inputs and outputs.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Genius 13300 points

    David-san,

    Thank you for the answer.

    Please let me check my understanding. Customer can connect following connection. 

    - Connect RX_AP+ and other IC USB3SSRX-

    - Connect RX_AP- and other IC USB３SSRX+

    In the above case,  customer needs to input the RX_Con + / RX_Con- connection with the polarity reversed. Is my understanding correct?

    Regards,

    Yamaguchi

     

     

  • 0 in reply to Takashi Yamaguchi
    TI__Guru**** 177071 points

    Yamaguchi-san

    For example, 

    Connect TUSB542 RX_AP+ and other IC USB3SSRX-, TUSB542 RX_CON+ can be connected to either + or -.

    Connect TUSB542 RX_AP- and other IC USB３SSRX+, TUSB542 RX_CON- can be connected to either + or -.

    The polarity swap supported is required by the USB spec, but please make sure the device meets USB spec polarity swap requirement.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Genius 13300 points

    Hi David-san,

    Thank you for your support. Customer understood it. 

    I received additional questions from the customer. Could you refer to the following file, and answer to the questions each case?

    /cfs-file/__key/communityserver-discussions-components-files/138/USB-P_2C00_-M-Swap.pptx

    The customer's case this time(above thread) is the case 1 in the file. In addition, there are cases 2 and 3 that are similar to that case, but with different parts that customer wants to swap.

    Could you please answer the questions listed for each case?

    Regards,

    Yamaguchi

  • 0 in reply to Takashi Yamaguchi
    TI__Guru**** 177071 points

    Yamaguchi-san

    The TUSB542 does not implement the polarity inversion. Per the USB3.0 spec

    During the TSEQ training sequence, the Receiver must use the D10.2 Symbol within the TSEQ Ordered Set to determine lane polarity inversion (Rxp and Rxn are swapped). If polarity inversion has occurred, the D10.2 symbols within the TSEQ ordered set will be received as D21.5 instead of D10.2 and the receiver must invert the polarity of the received bits. This must be done before the TSEQ symbols 1-15 are used since these symbols are not all symmetric under inversion in the 8b/10b domain. If the receiver does not use the TSEQ training sequence, then the polarity inversion may be checked against the D10.2 symbol in the TS1 ordered set.

    So the polarity inversion is always done by the host or the external device receiver.

    Thanks
    David