spice convertion to ibis , help.

Dear Ibis Users,

I need help to convert spice model from download manufacturer site to
IBIS model.

I have download the s2ibis2 software and i recompile it with the fix.
I have the spectre generator and the spice3 generator. ( no hspice or
spice generator : where can i find this other generator?)

I can generate the examples models from the s2ibis2 software and i have
understand what i need to make a pre-model file ( *.s2i) before running
s2ibis2.
But i don't understand the reason why it is necessary to have 2 models
files : spectre.mod + buffer.sp (ex1 and other)

Generally , manufacturers provide only one file which is *.mod or *.cir
or *.lib but i don't know the different.

Someone could help me on this topics ?

I thank everyone to answer.

Regards,

--
Frank AZEMA                      ALCATEL BUSINESS SYSTEM
Technical Direction             1 rt du Dr A. Schweitzer
Tel:+33(0)3.88.67.77.00    67000 ILLKIRCH Cedex - France
Fax:+33(0)3.88.67.70.83  Franck.Azema@sxb.bsf.alcatel.fr