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Altera_Forum's avatar
Altera_Forum
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12 years ago

2 FFs synchronizer constraint

Hi,

I am using a 2 FFs synchronizer in my design, and it requires a constraint that tells quartus to place the 2 FFs as close as possible to each other.

how do i set this constraint? is it in the sdc file? what is the syntax?

Thanks.

G.

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    set_max_delay -from FF1 -to FF2 1.0

    That puts a 1ns constraint on it. That's quick and easy. Note that TQ has metastability analysis tools, whereby you can get it to recognize synchronizers. The fitter then automatically puts them close together, and will calculate an MTBF for each synchronizer and the whole design. This takes more work though, which is why most people do the first.