Path delay fault simulation of sequential circuits

Abstract

To analyze path delay faults in synchronous sequential circuits, stimuli are simulated in a dual-vector mode. The signal states represent the logic and transition conditions for two consecutive vectors. After the simulation of each vector, only the activated paths are traced and the corresponding fault effect, if propagated to a flip-flop, is added to its fault list. A path numbering scheme avoids storage of path data which can be generated, if needed, from the path number. The simulation is independent of the specific delays of the combinational elements, and either robust or nonrobust detection can be simulated as options to the user. For robust simulation, an update rule for state variables is proposed whereby a flip-flop is updated with its correct value, provided it is a destination of at least one robustly activated path. This rule gives a higher and more realistic coverage of robustly detected faults. Experimental results verify the effectiveness of the simulator.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>