APPLICATION OF ADAPTED PETRI NETS FOR SIMULATION OF LOGIC SCHEMES DESCRIBED ON BEHAVIOR LEVEL

In logical modeling there is such concept as a race condition – a state at which several input signals switch at the same time, creating ambiguity of an output state. For elimination of such ambiguity it is proposed to use such mathematical apparatus which will allow to simulate parallel events. The main algorithm for simulation of digital circuits, applied in digital simulators, is the algorithm of the event driven simulation. However, the implicit choice of the sequence functioning of simultaneously switching signals may lead to an appearance of differences in the obtained simulation results. A new algorithm of the event driven functional simulation of digital integrated circuits, based on application of the adapted mathematical apparatus of the Petri nets, has been proposed. In the apparatus of the Petri nets the parallel constructions are imitated using the sequential instructions. Hence, there is no need to separate the events using delta-delays. It has been shown that the described approach enables to eliminate the ambiguity of switching signals, which occur at the same time due to failure because of using the delta-delay. The results of the algorithm work have been presented on an example of simulation on behavioral and the gate level of combinational and sequential schemes have been presented. The obtained time diagrams as well as the simulation time show that the algorithm proposed does not yield to existing simulation tools in terms of reliability and simulation time.

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