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DS250DF230: positive / negative signal swap for TX and RX

Ann_Lien
Genius 14330 points
Part Number: DS250DF230

Hello expert,

Customer want to know if they can swap positive / negative signal for TX and RX in order for ease on layout. Could you kindly help to answer it? Thanks a lot!!

Best regards,

Ann Lien

  • 0
    TI__Mastermind 19235 points

    Hi,

    The TI retimer CDR is polarity agnostic, so CDR will be able to achieve lock and output will be present if the data and databar signals are swapped. If the user does this the output bit polarity is obviously flipped relative to input signal.

    Regards,

    Rodrigo Natal

    HSSC Applications Engineer

  • 0 in reply to Rodrigo Natal
    TI__Genius 14330 points

    Hello Rodrigo,

    So the answer is no, right? Thanks!

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Mastermind 19235 points

    Sorry, I may have misunderstood your question. It is possible for the customer to use the retimer to invert the data polarity. If the polarity for all of the FIR taps is inverted then the output polarity is flipped relative to the input. See below info taken from the programming guide.

    Table. Invert the Polarity of the Output Data

    STEP

    SHARED/ CHANNEL REGISTER SET

    OPERATION

    REGISTER ADDRESS [HEX]

    REGISTER VALUE [HEX]

    WRITE MASK [HEX]

    COMMENT

    1

    Channel

    Write

    3D

    80

    80

    Enable FIR

    2

    Channel

    Read

    3D

    Read main-cursor polarity (bit

    6)

    3

    Channel

    Read

    3E

    Read pre-cursor polarity (bit

    6)

    4

    Channel

    Read

    3F

    Read post-cursor polarity (bit

    6)

    5

    Channel

    Write

    3D

    Invert bit 6 from step 1

    40

    Invert the polarity bit for the main-cursor

    6

    Channel

    Write

    3E

    Invert bit 6 from step 2

    40

    Invert the polarity bit for the pre-cursor

    7

    Channel

    Write

    3F

    Invert bit 6 from step 3

    40

    Invert the polarity bit for the post-cursor
  • 0 in reply to Rodrigo Natal
    TI__Genius 14330 points

    Hello Rodrigo,

    Thanks for your reply and will let customer know if, thanks!

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Genius 14330 points

    Hello Rodrigo,

    Customer use two retimers on this case and they would like to know if they can change only one chip polarity and remain one chip polarity as default. Reason is that their connector is custom and the connection would be easier if they change polarity with the one chip in these two retimers. Thanks a lot!

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Mastermind 19235 points

    It would be ok to invert polarity on only one retimer and not the other.

    Cordially,

    Rodrigo Natal

  • 0 in reply to Rodrigo Natal
    TI__Genius 14330 points

    Hello Rodrigo,

    Thanks for confirmation and will let customer know it :)

    Best regards,

    Ann Lien