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lizhang86
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Registered: ‎04-25-2017

rfsoc data converter fail timing

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Hello, forum

I keep hitting this timing issue between mts_clk/sync_2 register to rf data converter.  It seems to be part of the logic dealing with sysref and multi-tile synchronization.  I'm not sure if I can safely ignore this timing violation.  Could anyone help answer the following questions:

Since there is a 45 degree phase difference between source clock pl_adc_clk and destination clock pl_adc_clk_45.  The set_max_delay equal to source clk's period will effectively place the sampling edge of the destination clk 1/8th of the period after data's arrival.  See below for a visual explanation. 

20190815_164538.jpgIf this is true, then as long as my setup slack is smaller than 1/8 of the clock I could ignore the timing violation.  Is above assumption correct?  If that's correct, is there any logic that prevents the design using a 90 degree, or even better, 180-degree phase shift between these two clocks?  

I also modified the following two constraints based on my axis4_stream_clock for adc (491.52MHz)and dac(384Mhz).  Can anyone verify if these two constraints should be based on the axis4_stream_clock with respective adc and dac?

set_max_delay -from [get_clocks mts_clk_pl_clk_dac] -to [get_clocks mts_clk_pl_dac_clk_45] 2.6
set_max_delay -from [get_clocks pl_clk_adc_1] -to [get_clocks mts_clk_pl_adc_clk_45] 2.034

The following is the path that failed timing.  Any help appreciated.  

Capture.JPG

Thanks,

Li

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lizhang86
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Registered: ‎04-25-2017

 

Update: 

Found the answer,  Avrumw has a very good explanation in this post https://forums.xilinx.com/t5/Timing-Analysis/delay-vs-phase-shift-in-timing-analysis/td-p/863637.

Also, ug906 chapter 5: phase shift in timing report section.  

Li

 

 

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lizhang86
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Registered: ‎04-25-2017

 

Update: 

Found the answer,  Avrumw has a very good explanation in this post https://forums.xilinx.com/t5/Timing-Analysis/delay-vs-phase-shift-in-timing-analysis/td-p/863637.

Also, ug906 chapter 5: phase shift in timing report section.  

Li

 

 

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