A Hierarchical Simulation Environment for VLSI

In order to aid the debugging of complex circuits, our multiple-window hierarchical object-oriented simulation environment for VLSI circuits provides powerful features for navigation in the cell hierarchy of the simulated circuit. The environment mimics this hierarchy in that each cell (instance) is treated as an object which can show its structure (static) and simulation state (dynamic signal values, probes, etc.) in its own screen window. The structural description is obtained from a circuit database. The dynamic description is accessed by interposing virtual cell simulation objects between the interface and the simulator. These objects map the possibly flattened simulation structure back onto the structural hierarchy and provide a homogeneous access for controlling the simulator and for observing the simulation results in every cell. The parallel object hierarchies of structure, dynamic descriptors and interface windows allow easy replacement of objects in a simulation at multiple levels of abstraction, and it can be adapted for a distributed simulator.