Xic contains a ``hypertext'' capability, which is active in electrical mode. By default, the names of circuit nodes and devices are internally assigned, implying that the name of a particular device or node name of a particular wire net might not be well defined. This poses a problem when one wishes to identify a specific device or wire net by name. The hypertext feature addresses this issue, as do the node name mapping and name property assignment features.
This is necessary, for example, when setting device properties which reference other devices or nodes. The device names and node numbers might change, thus property text could become invalid if it were static. Instead, internally, strings are stored as data structures which reference pure text as well as devices and nodes by internal reference. Thus, these hypertext strings are always valid.
One creates a hypertext reference by clicking on the schematic while text input is being solicited in the prompt area. The returned data can be a node reference, a device branch reference, or a device name. The string, as currently defined, is inserted into the displayed text in the prompt area in color. Note that one can only delete the whole item with the Delete and Backspace keys, the hypertext references are treated as single items.
<p> One will encounter hypertext when using the prompt line editor as itemized below. In these cases, one could type in the text, however if due to future modifications that text changes, the present text would be wrong. If is therefor advantageous to use hypertext, by, e.g., clicking on a device in a drawing window rather than typing its name.
When creating a label, clicking on a connection point in the drawing, for example, will enter a hypertext link to the node into the label. The hypertext is shown in a different color in the prompt line. The label will always display the correct name for the node, should the name subsequently change. This is the means by which node labels can be added to the drawing.
There are three types of reference that can be defined by clicking in a schematic.
The node references and hidden targets are also the sensitive points when using the plot and iplot commands.
Note that these targets are active at any level of the hierarchy. However, they are generally not selectable unless the containing subcell is shown expanded as a schematic. If a subcircuit is shown as a symbol, one can still select internal points for hypertext references by using a proxy window. This is described in the next section.
This feature can be used to set up specialized SPICE output. Suppose one wishes to use a .save line in WRspice. A spicetext label can be created, where the nodes to be included in the save are inserted in the label by clicking on the drawing. The resulting .save line will always save the clicked-on nodes, whether or not the actual node names change.
For another example, suppose one needs to apply a functional dependence to a voltage source in the circuit to the voltage of some node. One would accomplish this with the following procedure.
The equation should appear in the property label near the voltage source. This could be, for example, ``2*v(4) + v(5)'', if default node names are used. Later, after modifying the circuit, one might notice that the label now reads ``2*v(6) + v(8)''. The internal node numbering has changed due to the modification, but the source still references the correct circuit nodes. This would not be the case if ordinary text was used for the equation string.