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NuvKFC's avatar
NuvKFC
Icon for Contributor rankContributor
3 years ago
Solved

How to constraint max skew between two net or balance the delay between two net?

I have two end point (two path) that need to balance the delay. The design is as follows. Path1: PAD1-->clock of module A: clock_a Path2: PAD2-->data of module A: data_a How t...
Nurina's avatar
Nurina
Icon for Regular Contributor rankRegular Contributor
3 years ago

Hello,


Thank you for the clear explanation.


You may find this training video useful: https://www.youtube.com/watch?v=RTcZOl2e8PI


You will have to add a synchronizer chain after path 1 as mentioned in the training video.

Could it be that the set_net_delay constraint is ignored because of a typo? It should be like so, it needs to be "-to" not "to":

set_net_delay -max 5.0 -from PAD1 -to clock_a


For set_max_skew you can try this rather than derive a value as mentioned in the video:

-get_skew_value_from_clock_period


Regards,

Nurina


  • NuvKFC's avatar
    NuvKFC
    Icon for Contributor rankContributor
    3 years ago

    Hi Nurina

    Thank you, Nurina, very much.

    Yes, to is a typo.

    And how to constraint the path from PAD1 to clock_a (Path1) and the path from PAD2 to data_a (Path2)?

    Path1 and Path2 aren't a grouped paths, like R2 to R3 in the video.

    I had tried following constraint. But "report_max_skew" command don't report any path.

    Constraint:

    set_max_skew 1.0 -from [get_ports {PAD1 PAD2}] \

    -to [get_nets {A|clock_a A|data_a}]]