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DS125DF410: Packet Lost at Rx in Low Temperature

Allan Fan
Expert 6700 points
Part Number: DS125DF410

Hi expert,

Customer used DS125DF410 x2 but has issue on U13 Rx side only that eye diagram can't properly open in low temperature -20 ~ -30degC. Would you please let us know what registers customer can tune and possibly improve it? Or what else we can check from hardware point of view to clarify the issue? 

status:

1. U11: no problem at all. 

2. U13: no problem at high temp and room temp. 0.51UI at room temp.

0.37UI at -30degC. 

Register config: 

note:

retimer0  is u11

retimer1  is u13

retimer new code.txt 
/retimer0 6 => 1  tx port
/retimer0 7 => 2 tx port
/retimer1 4 => 4 tx port
/retimer1 5 => 3 tx port

/retimer0 5 => 1 rx port
/retimer0 4 => 2 rx port
/retimer1 7 => 3 rx port
/retimer1 6 => 4 rx port

Reset channel registers, selfclearing.
i2c write retimer0 1 3 6 00 04
i2c write retimer0 1 3 7 00 04
i2c write retimer1 1 3 4 00 04
i2c write retimer1 1 3 5 00 04

i2c write retimer0 1 3 4 00 04
i2c write retimer0 1 3 5 00 04
i2c write retimer1 1 3 6 00 04
i2c write retimer1 1 3 7 00 04

assert CDR RESET
i2c write retimer0 1 3 6 0a 0C
i2c write retimer0 1 3 7 0a 0C
i2c write retimer1 1 3 4 0a 0C
i2c write retimer1 1 3 5 0a 0C

i2c write retimer0 1 3 4 0a 0C
i2c write retimer0 1 3 5 0a 0C
i2c write retimer1 1 3 6 0a 0C
i2c write retimer1 1 3 7 0a 0C

Select 10.31. Select 10.3125 Gbps standard rate mode for
i2c write retimer0 1 3 6 2F C0
i2c write retimer0 1 3 7 2F C0
i2c write retimer1 1 3 4 2F C0
i2c write retimer1 1 3 5 2F C0

i2c write retimer0 1 3 4 2F C0
i2c write retimer0 1 3 5 2F C0
i2c write retimer1 1 3 6 2F C0
i2c write retimer1 1 3 7 2F C0

Set Adapt Mode 1 or 0.
i2c write retimer0 1 3 6 31 20
i2c write retimer0 1 3 7 31 20
i2c write retimer1 1 3 4 31 20
i2c write retimer1 1 3 5 31 20

i2c write retimer0 1 3 4 31 00
i2c write retimer0 1 3 5 31 00
i2c write retimer1 1 3 6 31 00
i2c write retimer1 1 3 7 31 00

EQ=0x00, Select the right value depending on the channel loss.
i2c write retimer0 1 3 4 03 00
i2c write retimer0 1 3 5 03 00
i2c write retimer1 1 3 6 03 00
i2c write retimer1 1 3 7 03 00
Same as Reg_0x03
i2c write retimer0 1 3 4 3A 00
i2c write retimer0 1 3 5 3A 00
i2c write retimer1 1 3 6 3A 00
i2c write retimer1 1 3 7 3A 00
Same as Reg_0x03
i2c write retimer0 1 3 4 40 00
i2c write retimer0 1 3 5 40 00
i2c write retimer1 1 3 6 40 00
i2c write retimer1 1 3 7 40 00


Set fixed EQ setting value for divide by 4 and divide by 8 rates.
i2c write retimer0 1 3 6 3A 00
i2c write retimer0 1 3 7 3A 00
i2c write retimer1 1 3 4 3A 00
i2c write retimer1 1 3 5 3A 00


Power down DFE.
i2c write retimer0 1 3 6 1E 08
i2c write retimer0 1 3 7 1E 08
i2c write retimer1 1 3 4 1E 08
i2c write retimer1 1 3 5 1E 08

i2c write retimer0 1 3 4 1E 08
i2c write retimer0 1 3 5 1E 08
i2c write retimer1 1 3 6 1E 08
i2c write retimer1 1 3 7 1E 08

Configure VOD, 600 mV or 800mV.
i2c write retimer0 1 3 6 2d 00
i2c write retimer0 1 3 7 2d 00
i2c write retimer1 1 3 4 2d 00
i2c write retimer1 1 3 5 2d 00

i2c write retimer0 1 3 4 2d 0a
i2c write retimer0 1 3 5 2d 0a
i2c write retimer1 1 3 6 2d 0a
i2c write retimer1 1 3 7 2d 0a

Configure the tx DEM, -3 db.
i2c write retimer0 1 3 6 15 62
i2c write retimer0 1 3 7 15 62
i2c write retimer1 1 3 4 15 03
i2c write retimer1 1 3 5 15 03

Configure the rx DEM, 0 db.
i2c write retimer0 1 3 4 15 00
i2c write retimer0 1 3 5 15 00
i2c write retimer1 1 3 6 15 00
i2c write retimer1 1 3 7 15 00

Release CDR reset.
i2c write retimer0 1 3 6 0A 00
i2c write retimer0 1 3 7 0A 00
i2c write retimer1 1 3 4 0A 00
i2c write retimer1 1 3 5 0A 00

i2c write retimer0 1 3 4 0A 00
i2c write retimer0 1 3 5 0A 00
i2c write retimer1 1 3 6 0A 00
i2c write retimer1 1 3 7 0A 00

//serdes show 1 3 1 0 1000000 10000000
//serdes show 1 3 2 0 1000000 10000000
//serdes show 1 3 3 0 1000000 10000000
//serdes show 1 3 4 0 1000000 10000000

Regards,

Allan

  • 0
    TI__Mastermind 24272 points

    Hi Allan,

    Is there a difference in insertion loss between U11 and U13?  I'm curious if variation in insertion loss over temperature might impact this.  Also is the retimer locking and adapting to the signal at this cold temperature, or is it locking at another temperature and then ramped down to a lower temperature?

    In terms of what can be done to adjust this, typically CTLE and DFE are the best tools we have to work with to improve how the signal is equalized.  If we can better understand the mechanism that is causing the eye to degrade, this will help us understand how to approach the problem.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 10 points

    The retimer  locking at another temperature(50℃) and then ramped down to a lower temperature(-40℃).

    We are following the "Front-Port Ingress (Module-to-Host)" <snla323.pdf>, used the Adapt mode 0 (that is CTLE fixed, DFE Powered Down);Should we used the "DFE Powered up"?

  • 0 in reply to jian li
    TI__Mastermind 24272 points

    Hi Jian,

    The front-port ingress configuration recommends adapt mode 0 (manual adaptation) since many front port applications have very little insertion loss between the front port and the retimer.  We have also observed that in cases with very low insertion loss, automatic CTLE adaptation can sometimes continue to increase the CTLE index beyond 0, over equalizing the signal.  With that said, do you have an estimate for how much insertion loss is between the front port and retimer in your application.  Additionally, have you tried any of the adapt modes?  It would be valuable to check if adapt mode 1 or 2 have better eye openings.  If they do, it might be worth implementing some of the settings they adapt to.

    If you are observing eye closure as temperature is ramped down, it is worth trying to enable DFE and see how it impacts this.  You can use channel register 0x24[2] to re-adapt DFE at low temperature.

    Thanks,

    Drew