Interface Ports information
Interface ports provide connectivity between different levels of hierarchy and serve as named connectors in or out of a design. The interface port parameters specify the port name, its impedance, a reference node, and (optionally) one or more power, current, or voltage source specifications.
An interface port can have a source associated with it that provides excitation when the parent circuit is not part of the simulation. When a parent is simulated, port sources in a subcircuit have no effect and communication occurs between the parent and the child through the port. When the subcircuit is simulated directly, rather than as part of a parent simulation, excitation at ports (if any) is provided by port sources.
Similarly, a conservative interface port may have a sink associated with it. This may be a ground reference or an impedance (to ground). These have no effect when a parent is simulated, but are part of direct simulation of the subcircuit.
For conservative ports, the available sources and impedances depend on the port's nature. See Twin Builder Options: Port Options Tab for detailed information on setting up lists of port source and impedance components.
For non-conservative ports in a subcircuit, the symbol pin for the component shows the type as Input or Output.