Negative values in SDF

[engr]

Hi,

can some one please explain, what does the meaning of negative timing values in SDF file?

Thanks

 

[randyest]

I assume the negative value is in a cell hold check triplet, not interconnect, right?

Usually negative values in SDF are from negative-hold flops. In case you don't know, negative-hold DFF trade more setup requirement for less hold, to the point that negative hold time is required. These are often used for hold-time fix when there is plenty of setup slack.

 

[engr]

Thanks randyest.

Its like taking the advantate and setup and hold interdependency to fix the hold violations right, by having negative hold time at flop

 

[ljxpjpjljx]

because the library can support negative sdf, so the tools should also add compile option to support it!