using IBIS in HSPICE

Hi!

I tried to do some simulation in HSPICE with a differential driver in
IBIS format. The driver is a HSTL output and by connecting the driver
just to a simple 50 ohm load, I observed unrealistic sharp falling edge.
When I check the HSPICE log file, I have the following message:

 ** warning** iob_eles2:102:
    Inconsistency between Ramp and PD/PU data is detected.
    dV_f= 3.2680E-01 V_fwf_max= 3.3000E+00 V_fwf_min= 3.3000E+00
    transition from 80% to 20% is not satisfied

 ** warning** iob_eles2:186:
    099 instances of out-of-range states at falling ramp
    this can detriment accuracy

Any idea how I can correct the problem?

Thanks in advance.

Perry Qu