Test point insertion based on path tracing

This paper presents an innovative method for inserting test points in the circuit-under-test to obtain complete fault coverage for a specified set of test patterns. Rather than using probabilistic techniques for test point placement, a path tracing procedure is used to place both control and observation points. Rather than adding extra scan elements to drive the control points, a few of the existing primary inputs to the circuit are ANDed together to form signals that drive the control points. By selecting which patterns the control point is activated for, the effectiveness of each control point is maximized. A comparison is made with the best previously published results for other test point insertion methods, and it is shown that the proposed method requires fewer test points and less overhead to achieve the same or better fault coverage.