Differential pins in IBIS

Hello All,

I am attempting to create an IBIS model of an SSTL register. The register has 14 differential data inputs that are referenced to a common Vref input. How do I spec this in the IBIS model?

When they are added to the differential list I get an error stating:
"ERROR - Component 'sstv16857': inv_pin '35' is not unique."

See pin list:
[Diff Pin] inv_pin vdiff tdelay_typ
38 39 0 NA <-clock pins.
48 35 150mv NA <-Here down are data pins.
47 35 150mv NA
44 35 150mv NA
43 35 150mv NA
42 35 150mv NA
41 35 150mv NA
40 35 150mv NA
33 35 150mv NA
32 35 150mv NA
31 35 150mv NA
30 35 150mv NA
29 35 150mv NA
26 35 150mv NA
25 35 150mv NA

For a datasheet reference of a similar device please see:
http://www-s.ti.com/sc/psheets/scas625c/scas625c.pdf

Thanks.

-- 
Regards,
Stephen M. Nolan