The following digital models are supplied with XSPICE. The descriptions included below consist of an example model Interface Specification File and a description of the model's operation. This is followed by an example of a simulator-deck placement of the model, including the .MODEL card and the specification of all available parameters. Note that these models have not been finalized at this time.

Some information common to all digital models and/or digital nodes is included here. The following are general rules that should make working with digital nodes and models more straightforward:

1. All digital nodes are initialized to ZERO at the start of a simulation (i.e., when INIT=TRUE). This means that a model need not post an explicit value to an output node upon initialization if its output would normally be a ZERO (although posting such would certainly cause no harm).
2. Digital nodes may have one out of twelve possible node values. See 12.5.1 for details.
3. Digital models typically have defined their rise and fall delays for their output signals. A capacitive input load value may be defined as well to determine a load-dependent delay, but is currently not used in any code model (see 28.7.1.4).
4. Several commands are available for outputting data, e.g. eprint, edisplay, and eprvcd. Digital inputs may be read from files. Please see Chapt. 12.5.4 for more details.
5. Hybrid models (see Chapt. 12.3) provide an interface between the digital event driven world and the analog world of ngspice to enable true mixed mode simulation.