Why does SDF back annotate a wrong delay value on simulator?

[Peter Chang]

Dear Sir,

I met one strange thing that the cell delay value is different from the delay value in SDF file, while doing a post simulation. From the log file, the sdf file has been read. And only
have some unimportant warnings. Why is the cell delay value in SDF different from what
I see on simulator? Thanks.


Peter:sad:

 

[rca]

1- you backannotated the value with the correct (min:typ:max) from sdf?
2- negative value are change to zero in Questa simulator, for example.

 

[Peter Chang]

Yes. The IOPATH DELAY is

(IOPATH A Y (0.487::0.487) (0.466::0.466))

But the value I saw is 0.213 ns and 0.167ns on simulator.

I used ncverilog to generate FSDB and verdi to check
the waveform.


Peter

 

[rca]

So you backannotate wich the max or the min value, because the typical does not exist, right?

 

[Peter Chang]

Maximum. Thanks.

Peter