Non-Masking Non-Robust Tests for Path Delay Faults

A test set for transition faults detects smaller delay defects if transition faults are detected through longer paths. Conversely, this paper observes that it is advantageous for a test set for path delay faults, which targets small delay defects, to detect larger delay defects along the paths. The paper defines a notion of masking that prevents larger delay defects from being detected. It defines a non-masking non-robust test for a path delay fault that guarantees the detection of larger delay defects along the path. It also defines masking metrics that allow the level of masking of larger delay defects for a test, and a test set, to be evaluated. Using these metrics, the paper describes a procedure that computes a test set for path delay faults with reduced levels of masking for larger delay defects. Experimental results are presented to demonstrate the extent to which masking of larger delay defects occurs under tests for path delay faults in benchmark circuits.