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DS280DF810: DS280DF810 with auto-nego

Yang PETER
Prodigy 30 points
Part Number: DS280DF810
Other Parts Discussed in Thread: DS280BR820, DS280BR810

Tool/software:

Hi Ti team

I have a project use DS280DF810 x2 for 2x QSFP28 port.

So I have 8 Tx serdes and 8 Rx serdes.

One DS280DF810 connect with all of TX signal , another one DS280DSF810 connect with all of RX signal .

The DS280DF810 was on switch A  the output port was QSFP28 , and the Switch B with SFP+*4.

We set the switch A QSFP port as breakout mode 4*10G connect switch B SFP+*4 via QSFP to SFP*4 breakout DAC cable.

Due to cable was DAC , we will enable auto-nego and link-training on both switch.

Note : DS280DF810 was setting on 10G mode in this time.

 

We found the port link up will take long time when auto-nego enable.

IF disable auto-nego and link-training , we will not observed this behavior.

In general use , if we use dac cable , we need enable auto-nego and link training.

In particular , our serdes support 25G and 10G speed.

Also in data sheet , it shows 

"For applications which require IEEE802.3 100GBASE-CR4 or 25GBASE-CR auto-negotiation and link training, a
linear repeater device such as the DS280BR820 (or similar) is recommended."

Could you let me know the detail or rule for that ?

Does DS280DF810 support copper cable with auto-nego ? 

thanks

PEter

  • 0
    Prodigy 30 points

    Update ~

    Hi Ti Team 

    When config as 4x10G link takes approximately 5 minutes to come up.

    Mac side media type : 10G-KR + Auto-nego + link-training

    When config as 4x25G breakout two links are continuously flapping.

    Mac side media type : 25G-CR + Auto-nego + link-training.

    ##################################################

    I also saw the case feedback about the auto-nego and link training on Fourms.

    https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1513866/ds280df810-ds280df810-and-kr---sfi-conversion?tisearch=e2e-sitesearch&keymatch=DS280DF810#

    Should I config the DS280F810 to Raw mode (CDR bypass) before I enable the auto-nego ?

    If yes , could you let me know about the setting ?

    thanks

    PEter

  • 0 in reply to Yang PETER
    TI__Mastermind 18950 points

    Hi Peter,

    Our team is currently on US holiday. We will get back to you next week.

    Best,

    Evan Su

  • 0 in reply to Evan Su
    TI__Mastermind 36803 points

    Hi Peter,

    • Auto-negotiation takes place at 312.5 Mbps.  To support auto negotiation, you must enable RAW data output when CDR is not clocked.  You can enable this by setting channel register 0x1E[7:5]=0.  See programming guide for details on register.
    • The DS280DF810 does not support link training.

    Thanks,
    Drew

  • 0 in reply to Drew Miller1
    Prodigy 30 points

    hi Drew

    Sorry~ late for the response.

    About the 0x1E setting , my default value was 0xe3.

    I change the 0x1E form 0xe3 to 0x03.

    After that I initial the port as 4X10G and connect to another switch 4 port SFP+.

    If enable the auto-nego , I saw  link up 2 ports in sometimes or sometimes link up 3 ports.

    Is it correct behavior ? Or I need check CDR status first ?

    thanks

    PEter

  • 0 in reply to Yang PETER
    TI__Mastermind 36803 points

    Hi Peter,

    Did you disable link training?  I would recommend reviewing the CDR and signal detect status to better understand the status from the retimer perspective.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 30 points

    Hi Drew

    0x18 was retimer A for TX signal. 0x19 was retimer B for RX signal.

    I saw the retimer A exist CDR unlock  but retimer B under lock status. 

    root@(none):/# i2cget -y 0 0x18 0x78
    0x20
    root@(none):/# i2cget -y 0 0x18 0x78
    0x20
    root@(none):/# i2cget -y 0 0x18 0x78
    0x20
    root@(none):/# i2cget -y 0 0x18 0x78
    0x20
    root@(none):/# i2cget -y 0 0x18 0x1E
    0x03
    root@(none):/# i2cget -y 0 0x19 0x1E
    0x03
    root@(none):/# i2cget -y 0 0x19 0x78
    0x30

    It's seem that Broadcom driver keep enable the DFE and link-training when system enable the Auto-nego.

    And Mac serdes keep receive the remote /local fault and cause those ports link down .

    If disable the AN + LT , those ports link well.

    root@(none):/# ps xe12-xe15
                     ena/        speed/ link auto    STP                  lrn  inter   max   cut   loop
               port  link  Lns   duplex scan neg?   state   pause  discrd ops   face frame  thru?  back
          xe12( 29)  down   1   25G  FD   SW  Yes  Forward  TX RX   None   FA     KR 12284
          xe13( 30)  up     1   10G  FD   SW  Yes  Forward  TX RX   None   FA     KR 12284
          xe14( 31)  down   1   10G  FD   SW  Yes  Forward  TX RX   None   FA    XFI 12284
          xe15( 32)  up     1   10G  FD   SW  Yes  Forward  TX RX   None   FA     KR 12284

    root@(none):/# phy control xe12
    Current PHY control settings of xe12 ->
    Preemphasis              = 0x1b4405
    DriverCurrent            = 0xffffffff
    DFE ENable               = True
    LP DFE ENable            = False
    BR DFE ENable            = False
    LinkTraining Enable      = True
    Interface                = 0xb
    CL74                     = False
    CL91                     = False
    CL108                    = False
    root@(none):/# phy control xe12
    Current PHY control settings of xe12 ->
    Preemphasis              = 0x1b4405
    DriverCurrent            = 0xffffffff
    DFE ENable               = False
    LP DFE ENable            = False
    BR DFE ENable            = False
    LinkTraining Enable      = False
    Interface                = 0x27
    CL74                     = False
    CL91                     = False
    CL108                    = False

    if I change to DS280BR820 , can it support Auto-nego and Link-Training ?

    Could you let me know the difference between DS280BR820 and DS280BR810?

    thanks

    PEter

  • +1 in reply to Yang PETER
    TI__Mastermind 36803 points

    Hi Peter,

    I'm wondering if disabling AN is an option for this application.

    The DS280BR820 can support auto-negotiation and link-training since this is a linear redriver device.

    The DS280BR810 has AC coupling capacitors on RX and TX.  The DS280BR820 only has AC coupling capacitors on RX.  Due to removal of AC coupling capacitors on DS280BR820, it has improved high speed performance relative to DS280BR810.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 30 points

    Hi Drew

    Got it , thanks your support.

    We will evaluate DS280BR820 with customer.

    thanks

    PEter

  • 0 in reply to Yang PETER
    Prodigy 30 points

    Hi Drew

    Sorry one more question.

    Does DS280BR820ZBLR pin to pin compatible with DS280DF810ABVR ?

    thanks

    PEter

  • 0 in reply to Yang PETER
    TI__Mastermind 36803 points

    Hi Peter,

    Yes it is pin to pin compatible, but note that DS280BR820 requires external AC coupling caps on TX.  DS280BR810 has integrated AC coupling caps on TX, but DS280BR820 has better high speed performance than DS280BR810.

    Please see app note below on co-designing DS280BR8x0 and DS280DF810.

    https://www.ti.com/lit/an/snla475/snla475.pdf

    Thanks,

    Drew