Harmony Widget for X-free scan testing

摘要

This paper presents a simple innovative Design for Test (DFT) solution for removing one of the major sources of Xs (unknown outputs) during scan testing. The DFT called Harmony Widget is inserted at state elements that a scan test may load with illegal or unspecified state thus causing circuit to misbehave or produce indeterminate or unknown outputs (Xs). The DFT used is far simpler than the current practice in industry and blends with the prevailing scan design methodologies.