SDF Error: Negative Delay ignore and replace by 0

[donald007]

negative delay in sdf

Dear all,
I am running post simulation. I got the following message.
"SDF Error: Negative Delay ignore and replace by 0"


What does this mean?
Is it important?
Can I ignore it?

Thanks,
Donald YEH

 

[jankindt]

sdf negative

It means that your SDF file contains negative delay values.

If you have for example a negative hold value -x, your signal can change x time before the clock event and still not violate the hold requirement.
Your simulator is not accepting these negative values and is setting them to 0. By doing so, the simulator is making the constraints tougher. So if your simulation passes, you can trust on that result.

You might have a compile switch to have the simulator accept those negative values. Bare in mind that your simulation library needs to be capable of correctly simulating this also.