A Hierarchical Simulator Based on Formal Semantics

Abstract

Simulation consists of exercising the representation of a design on a general purpose computer. It differs from programming only because the ultimate implementation will be in a different medium, say a VLSI chip. In order for simulation to be in any sense effective, the simulated system must perform the same function as the ultimate implementation. A VLSI chip is a highly concurrent object; the simulation of such a chip amounts to programming a highly concurrent system. It follows that any demonstrably correct simulation technique will be one of the two types: (1) The entire design is represented as an implementation with objects which are abstract models of the medium at the bottom level (e.g. transistor model). The simulation operates on a representation which is a direct image of the fully instantiated implementation in the medium. (2) The design is represented as a hierarchy of implementations. Each level of implementation is constructed of objects which are abstract models of the implementation at the level below it. The simulation operates on a hierarchical representation where each level is refined by the level below it.