When Xic generates a SPICE netlist, it automatically includes the text of the required models. For MOS devices, i.e., devices keyed by the letter `m', a spatial binning model selection scheme is available. This same binning mode is available for MOS devices in WRspice. When running WRspice from Xic, the SPICE text is composed by Xic, so the it is usually necessary to resolve the spatial binning within Xic.
Complete information is available in the description of the WRspice MOS model.
The L and W parameters values found in the MOS device param property are used to key different models. The model property specifies the basename of the model. The variations are found in the model library under the basename suffixed with ``.1'', ``.2'', etc. Each of these models may contain parameters LMIN, LMAX, WMIN, WMAX which specify the parameter window for the model. The model with the window containing the device L/W is the one chosen. If a model is missing one of the min/max parameter sets, it will match any value of the parameter.