Path delay faults and ENF

Single path delay faults (PDFs) are considered. They are reduced to temporal faults of ENF literals. These temporal faults exist during delay time of the relevant paths and then disappear. Deriving test pair v₁, v₂ for robust and non-robust PDFs is based on analyses of products of free fault and fault ENF. Some properties of these test pairs are determined. Possibilities of using these properties to cut the length of the test detecting all PDFs of a combinational circuit are shown.