Automatic modeling of switch-level networks using partial orders

A key idea in switch-level simulation is the use of a total ordering of signal strengths to resolve conflicts between opposing signals. For many circuits, however, it is not possible to assign such strengths to circuit elements in a logically consistent fashion without user intervention. It is shown that the use of a partial ordering of strengths avoids these difficulties and allows modeling to be done automatically. The authors also discuss the need to minimize the number of distinct strengths needed to model a circuit, because simulation times are affected by the number of strengths being used. This is especially important for compiled switch-level simulators that generate representations whose size is proportional to the number of strengths. Statistics on the application of these ideas to industrial chips are presented.<>