Graceful Degradation of Reconfigurable Scan Networks

Abstract

Modern integrated circuits (ICs) include thousands of on-chip instruments to ensure that specifications are met and maintained. Scalable and flexible access to these instruments is offered by reconfigurable scan networks (RSNs), e.g., IEEE Std. 1687. As RSNs themselves can become faulty, there is a need to exclude and bypass faulty parts so that remaining instruments can be used. To avoid keeping track and updating description languages for each individual IC, we propose an on-chip hardware block that makes adjustments according to the fault status of a particular IC. We show how this block enables test for faulty scan chains, localization of faulty scan chains, and repair by excluding faulty scan chains. We made implementations and experiments to evaluate the overhead in terms of transported data and area.