I have made a lot of models from spice using SPI2MOD. For the most
accurate model, you should use the VT waveforms and not the 10290. You
will have to give two sets of waveform data. they should be generated
with loads of 50ohm to VCC and 50ohm to gnd (for CMOS). This turns out
to be the same manner used in IBIS (see IBIS cookbook on the IBIS web
page). You should not change the time scale of the input data as long as
you use the same input waveform to excite the signals in the spice deck
(ie. use the same spice deck, just change the load). The only thing you
may want to adjust is the absolute error value in spi2mod (-ae). This
makes SPI2MOD use more points in the resultant file.
For more advice, I recommend you contact the Viewlogic support line or
you can send me more details (like the resultant XTK model).
Senior Scientist, Viewlogic Consulting Services