Additional Notes

This section provides some additional notes to clarify technical issues. Most of this information was developed as a result of customer interaction.

Keywords

Parameters fwf_tune , rwf_tune specify transition time for circuitry (either pullup or pulldown) that goes from the ON to OFF state as a fraction of time, delta_T , for a transition for the opposite circuitry (either pulldown or pullup) from OFF to ON state. The delta_T value for ramp data transition time is different from the value for single waveform transition time ( delta_T depends on parameters ramp_fwf and ramp_rwf). Consequently, the absolute values for transition time from the ON to OFF state are different for ramp data and single waveform data.

Voltage Thresholds

Voltages applied to the input node and enable node are digital signals. They should be either 0 or 1. It is acceptable to specify input voltage as:

V_in nd_in 0 pulse (0 3.3 0 0.5n 0.5n 4n 8n)

However, Star-Hspice currently detects only two thresholds, 20% and 80% of [0,1] swing, i.e., 0.2V and 0.8V. If a buffer is non-inverting and in a LOW state, it will start transition to a HIGH state, if V_in > 0.8V. If the buffer is in HIGH state, it will start the transition to LOW state, if V_in < 0.2V. Specifying input voltage in the range [0 , 3.3V] as in the above example does not make LOW -> HIGH transitions better in any way, but can add uncertainty over time interval 0.5ns, when the transition actually occurs.

.OPTION D_IBIS

The new option d_ibis is introduced to specify the directory where IBIS files are located. Example of usage:

.OPTION d_ibis='/home/user/ibis/models '

If several directories are specified, then Hspice will look for IBIS files in the local directory (the directory where Hspice is run), then in the directories specified through .option d_ibis in the order that .option cards appear in the netlist. At most, four directories can be specified through d_ibis option. Examples of usage:

.OPTION d_ibis='/nfs/port/user/hspice/run/subckt/optd'

+ buffer nd_pu nd_pd nd_out nd_in

+ file = 'opt.ibs'

+ model = 'DS92LV090A_DOUT'

Option d_ibis is case-sensitive.