Test Point Insertion with Control Points Driven by Existing Functional Flip-Flops

Abstract

This paper presents a novel test point insertion method for pseudorandom built-in self-test (BIST) to reduce the area overhead. The proposed method replaces dedicated flip-flops for driving control points by existing functional flip-flops. For each control point, candidate functional flip-flops are identified by using logic cone analysis that investigates the path inversion parity, logical distance, and reconvergence from each control point. Four types of new control point structures are introduced based on the logic cone analysis results to avoid degrading the testability. Experimental results indicate that the proposed method significantly reduces test point area overhead by replacing the dedicated flip-flops and achieves essentially the same fault coverage as conventional test point implementations using dedicated flip-flops driving the control points.