In order to actually simulate a circuit that has been extracted from the physical layout, it is necessary to add sources and perhaps other devices, which have no counterparts in the physical layout. In general, this will cause LVS errors in subsequent LVS runs. The nophys property can be added to the additional devices to avoid these errors.
By ``ignoring'' these devices, the device terminals are considered as open circuits. However, there are times when it would be useful to consider these devices as shorted. For example, suppose that one wishes to include parasitic series inductance in a resistor during simulation. However, this inductance would cause LVS to fail, since the series inductor added to the schematic has no explicit physical counterpart.
It is possible to configure the nophys property to indicate that when the electrical netlist is generated for use by the extraction system, the corresponding devices will be forced such that all terminals connect to the same net, i.e., the terminals are effectively shorted together. Thus, the inductor in the example above, if given this property, would disappear properly during LVS.
The numerical value of the property is 5. The property string is either ``nophys'' or ``shorted''. The latter indicates that the shorting feature is to be used. Xic will always set the property string to one of these values. Devices inherit this property from cell definitions in the device library file. The format is
5 5 nophys; or
5 5 shorted;
Devices with the nophys property applied will be rendered using a different color than other devices.