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akhtar2510
Contributor
Contributor
959 Views
Registered: ‎09-26-2018

DDR4 clk to DQS Skew

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I want to simulation Kintex ultrascale  and DDR4 in Hyperlynx . After simulation , Read ,Write , Address and diffrencial pairs are OK, but i have problem in clk to DQS Skew.

I must be change track size of lane  or set delay in lane pins.

can i set delay for pins ?

how can i solve clk to DQS skew problem ?

please help me

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deepalir
Xilinx Employee
Xilinx Employee
820 Views
Registered: ‎02-21-2019

Hi @akhtar2510 

The general guideline and requirement is CK/CK# must arrive after DQS/DQS# at each memory component to ensure calibration can align DQS/DQS# to the correct CK/CK# clock cycle. The Ultrascale device memory controller can internally delay the DQS line to account for negative skew. 

Please refer to UG583 -General Memory Routing Guidelines section, skew constraints range and trace lengths for more information. 

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deepalir
Xilinx Employee
Xilinx Employee
821 Views
Registered: ‎02-21-2019

Hi @akhtar2510 

The general guideline and requirement is CK/CK# must arrive after DQS/DQS# at each memory component to ensure calibration can align DQS/DQS# to the correct CK/CK# clock cycle. The Ultrascale device memory controller can internally delay the DQS line to account for negative skew. 

Please refer to UG583 -General Memory Routing Guidelines section, skew constraints range and trace lengths for more information. 

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watari
Teacher
Teacher
810 Views
Registered: ‎06-16-2013

Hi @akhtar2510 

 

Did you consider the following typologies to resolve DQS skew issue ?

 

- Fly-by topology

- Clamshell topology

 

Best regards,

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kshimizu
Xilinx Employee
Xilinx Employee
780 Views
Registered: ‎03-04-2018

Hello @akhtar2510 ,

 

Xilinx does not support any changes in the IP.  As @deepalir mentioned, memory controller adjust the delay based on the FPGA package delay and PCB skew.  Please check the PCB guideline and routing.

 

 

Best regards,

Kshimizu

 

Product Application Engineer Xilinx Technical Support

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akhtar2510
Contributor
Contributor
745 Views
Registered: ‎09-26-2018

Thank you

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