how to avoid this warning?

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Hi,

if you really would to get rid of the warning you can use the assignment editor:

Assignments -> Assignments Editor -> ( fill in node name in the "to" column) -> choose assignment "not a clock". Don't forget to set the Value to "on".

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THX for your help first.The method you mentioned above i have tried，but the

warning is still，and another warning happens：

Warning: Found invalid timing assignments -- see Ignored Timing Assignments report for details。

No timing path applicable to specified destination。

By the way，the signal “flg_oc_1” is a internal variable，not a IO。