A Fault-Collapsing Analysis in Sequential Logic Networks

Abstract

Although a sequential circuit M reduces to a combinational network C M after all feedback paths have been cut, an application of Bossen and Hong's checkpoint labeling procedure to C M does not necessarily yield a minimal solution. The set of checkpoints so obtained will include all feedback lines. In this paper, it is shown that these feedback lines are not necessary checkpoints under a “delay equivalence” relation. In addition to this, we also show that not every fanout branch is a necessary checkpoint. Any “singular fanout branches” can be removed from consideration. The results of our analysis lead to a minimal checkpoint labeling procedure for sequential logic networks.