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How to constraint min delay between LCELLs?

NuvKFC
New Contributor I
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Some asynchronous need to use LCELLs to generate pulses, like following example.

However, the delay of LCELLs is different on the difference FPGA device.

So, I use following constraints to constraint the min delay of LCELL. 

But it doesn't work.

How to constraint min delay between LCELLs?

Thank you very much.

 

Ex.:

lcell dly1d (.out(y1), .in(A) );

lcell dly4d (.out(y), .in(y1) );

 

Constraints:

set_min_delay 5.0 -from [get_pins dly1d|combout] \

                                  -to      [get_pins dly4d|combout]

set_net_delay -min 5.0  -from [get_pins dly1d|combout] \

                                            -to      [get_pins dly4d|combout]

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Nurina
Employee
2,203 Views

Hi,


Right so I don't think this constraint works on LCELLS alone. Because you would need a setup/hold relationship in the first place.

Which brings us back to using set_data_delay, which definitely should work on LCELL alone.

Since it isn't supported on Quartus II 13.1, I suggest you migrate to Quartus Standard 21.1 as this would have the set_data_delay.


On the other hand, you are using LCELL to generate a pulse to wake up the clocks right? Maybe you could consider using clock control IP: https://www.intel.com/content/dam/support/jp/ja/programmable/support-resources/bulk-container/pdfs/literature/ug/ug-altclkctrl.pdf


Regards,

Nurina


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26 Replies
NuvKFC
New Contributor I
472 Views

Hi Nurina
    Thank you, Nurina, very much.

 

OK. I  get it. Thank you very, very much. ^.^

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NuvKFC
New Contributor I
470 Views

Hi Nurina
    Thank you, Nurina, very much.

 

Sorry that I have a question.

 

Using set_min_delay need a setup/hold relationship on that path.

Why set_net_delay can't work on LCELLS?

 

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Nurina
Employee
462 Views

Hello,


Just like set_max/min_delay, set_net_delay requires the path to have a setup/hold relationship (reg to reg path). So it doesn't go through comb logic.


Regards,

Nurina


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NuvKFC
New Contributor I
456 Views

Hi Nurina
    Thank you, Nurina, very much.

 

OK, I get it. Thank you very, very much.

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Nurina
Employee
455 Views

Hello,


No problem! I’m glad that your question has been addressed, I now transition this thread to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.

 

Regards,

Nurina


P/S: If you like my comment, feel free to give Kudos. If my comment solved your problem, feel free to accept my comment as solution.


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NuvKFC
New Contributor I
448 Views

Hi Nurina
    Thank you, Nurina, very much.

 

OK. No problem! Thank you very, very much.

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