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DS100KR401 - 10G-KR mode

Hiroshi Katsunaga
Mastermind 6480 points
Other Parts Discussed in Thread: DS100KR401, DS80PCI402, DS80PCI800

Hello,

My customer has some questions about DS100KR401.

They want to use DS100KR401 for 10G-KR (Server) application between CPUs and LAN SW across a backplane.

Please help me.

[Q1]

In 10G-KR mode, Is the setting of the equalizer and de-emphasis automatically ? or manually ?

 [Q2]

Is there the detailed document about the operation in 10G-KR mode ?

If there are some figures, it looks good.

Best Regards,

Hiroshi Katsunaga

  • 0
    TI__Mastermind 29655 points

    Hi Hiroshi-san,

    Please see answers to questions below:

    1) No matter which mode you are in, you will need to set the equalizer and de-emphasis manually. 

    2) There is not a specific document available that addresses operation in 10G-KR mode. Operation in 10G-KR mode is similar to the Gen-3 mode operation in the PCIe repeaters. In order to facilitate link-training protocols required by the KR standard, the repeater should be placed in 10G-KR mode so that the output is more linearized  (compared to 10G Mode) in order to preserve overall signal transparency along the signal path between link partners.

    Thanks,

    Michael

  • 0 in reply to Michael Lu (Santa Clara)
    Mastermind 6480 points

    Hi Michael-san,

    Thank you for your fast response.

    I told your answers to my customer.

    I received an additional question from them.

    The additional question as follows. 

    [Q]

    The PCIe repeaters for example DS80PCI402 can not set de-emphasis manually in GEN3 mode.

    According to your answer, DS100KR401 can set de-emphasis manually in KR mode.

    both PCIe gen3 and 10G-KR support link-training protocols.

    Why can 10G-KR repeaters set de-emphasis manually ?

    Why can PCIe gen3 repeaters not set de-emphasis manually ?

    Please tell me the details more.

    I found that there was a mistake in DS100KR401 datasheet.

    [Error (probably)]

    ( datasheet P.4 Pin Descriptions DEMA0/1, EMB0/1 Pin descriptions)

    DEMA[1:0] and DEMB[1:0] control the level of de-emphasis of the output driver

    when in Gen1/2 mode.

    [Correct (probably)]

    DEMA[1:0] and DEMB[1:0] control the level of de-emphasis of the output driver.

    Is it right ?

    Best Regards,

    Hiroshi Katsunaga

  • 0 in reply to Hiroshi Katsunaga
    TI__Mastermind 29655 points

    Hi Hiroshi-san,

    Please see answers below:

    Both DS100KR401 and DS80PCI402 can set de-emphasis manually in KR and Gen-3 modes, respectively, by pulling Pin 21 via 1kOhm to VDD (or VIN, depending on the whether you are in 2.5V mode or 3.3V mode). 10G-KR mode invokes the same functionality as Gen-3 with de-emphasis, from the redriver's standpoint.

    You are correct. Gen 1/2 is a typo, since de-emphasis can be controlled whether in 10G-KR or 10G mode.

    Thanks,

    Michael

  • 0 in reply to Michael Lu (Santa Clara)
    Mastermind 6480 points

    Hi Michael-san,

    Thank you for your response.

    Please tell me about it a little in detail.

    There is the following description to the datasheet of DS80PCI402.

    I think de-emphasis does not function in Gen-3 mode (of DS80PCI402).

    Is it right ?

    Is 10G-KR mode (of DS100KR401) similar function ?

    [datasheet P.8 note (1)]

    The DS80PCI800 repeater in GEN3 mode is designed to be transparent,

    so the TX-FIR (de-emphasis) is passed to the RX to support the PCIe GEN3 handshake negotiation link training.


    Best Regards,

    Hiroshi Katsuanga

  • 0 in reply to Hiroshi Katsunaga
    TI__Mastermind 29655 points

    Hi Hiroshi-san,

    The statement you have pointed out is related to how VOD follows VID in a more linear manner than in Gen 1/2 mode in order to help pass TX-FIR conditioning better.

    I see though that there is still some confusion about whether there is de-emphasis from the repeater in Gen-3 mode. The reason that de-emphasis is not directly specified on the first page for Gen-3 is that the TX-FIR may be providing additional de-emphasis of its own. Therefore, for example, if we state that our part is providing -3.5 dB de-emphasis, this would be confusing, because we would actually be providing -3.5 dB de-emphasis mixed with what the TX-FIR is already providing.

    In both 10G-KR mode (for DS100KRxxx parts) and PCIe Gen 3 with De-emphasis (for DS80PCIxxx parts), de-emphasis is enabled and output VOD will track more linearly with input VID. To provide better transparency to pass the TX-FIR to the RX for link training negotiation, it is recommended to minimize the de-emphasis settings on the repeater when possible.

    Thanks,

    Michael

  • 0 in reply to Michael Lu (Santa Clara)
    Mastermind 6480 points

    Hi Michael-san,

    Thank you for your response.

    We understood your devices function.

    Best Regards,

    Hiroshi Katsunaga