Method for propagating unknown digital values in a hardware based complex circuit simulation system

摘要

In a circuit system simulation model which may comprise a combination of the physical device to be modeled and means for controlling the physical device at normal operating speeds, a method is provided for propagating a simulated unknown signal value which comprises exciting the simulation model with differing pattern sequences a plurality of times, during each excitation sequence changing at least one input value in the input sequence, comparing the sampled values of each resultant output signal, and setting or recognizing as an unknown value any specific output signal which differs as a result of the change in the input sequence. Modification, repetition, sampling and comparison of patterns may be repeated a number of times. Only a fraction of the possible input patterns need to be presented to indicate the propagation of unknown values.