Timing mismatch between SDF and RSPF

[sunrise]

Hi all,

Do you have ever met this case?
Timing result based on RSPF file is different from that based on SDF file.
The RSPF file was extracted from post-layout database by HyperExtract. And the SDF file was converted from that RSPF file by Pearl or PKS. The design can pass STA in PKS with RSPF file but cannot pass with SDF file.

I don't know what's difference between RSPF and SDF. but it seems very strange. Do you know how Pearl/PKS converts RSPF into SDF? And what's the difference of timing calculation algorithm for RSPF and SDF in Pearl/PKS.


-sunrise

 

[yasonwang]

Is timing difference from different clock domains?

SDF represents worst timing arc, but rspf can be used by delay calculator to compute multiple timing arcs between two nodes, especially for crossing region of different clock domains.

For STA, we only trust in rspf results.

 

[haosg]

right, for STA, we should trust on parasitisc extraction.
the SDF is only for simulation.

 

[kfy]

F.Y.I

you can use primetime to get a accuracy timing !
or
use celtic-dc to generate a accuracy SDF !

 

[diablo1222]

The rspf represents RC delay in terms of a pi model(2C's and 1 R). The accuracy of this model is better than sdf format.

 

[daniel@2004]

we only trust the result from PT + RSPF

 

[funzero]

THEY USE DIFFERENT TIMING MODEL , AND THE RESULT MAY BE A LITTLE DIFFERENT.

 

[siawklai]

When using SDF file for postlayout STA, you also need set_load/set_resistance file as SDF file didn’t contain of capacitance and transition times information.

 

[Atre]

Ca anyone explain how to annotate dspf into PrimeTime or so? Cause I am encountering problems in doing that. Is there a flow or something?

Thanks in advance!