Software interfaces for integrated simulation applications

In integrated simulation applications, simulation tools interact with other components of computer-aided-design systems at the level of internal structures, sharing some internal data and communicating through procedural invocations. There are two basic types of interactions between interacting tools, the so-called reverse and indirect communication methods. Reverse communication returns to the invocation environment after each required task; it is a rather flexible technique, but it requires global control methods which can be quite unreliable and difficult for modifications in nontrivial applications. Indirect communication uses local control at different levels of hierarchical organization, passing global information from one level of the hierarchy to another; it corresponds thus to hierarchical structure of tools and to different levels of abstraction at different levels of hierarchy. Several integrated applications built around a circuit simulation environment are described, and interfaces designed for the integration of different tools are discussed