User`s guide

Interface Subcircuit Selection by PSpice A/D 15
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it provides a more accurate, less optimistic answer. However,
this behavior may not be appropriate when the input rise and fall
times are long, or when the input voltage never leaves the
threshold region. If this is the case, you may want to use the level
2 interface.
Level 2 Interface
The level 2 AtoD interface transitions directly from 0 to 1 and 1
to 0 without passing through intermediate R, F, or X levels. That
is, an exact switching voltage is assumed (again, the specific
voltage depends on the technology you are using). It provides a
more optimistic, and therefore less accurate, response than level
1. Level 2’s behavior is appropriate when the input voltage
oscillates around the threshold voltage.
Simulations can therefore avoid getting bogged down with the
greater detail of R, F, and X states around these oscillations.
Thus, you may want to specify level 2 on only those devices for
which this behavior is critical to a successful simulation. This
mechanism is described below.