Test Cost Reduction for X-Value Elimination By Scan Slice Correlation Analysis

Abstract

X-values in test output responses corrupt an output response compaction and can cause a fault coverage loss. X-Masking and X-Canceling MISR methods have been suggested to eliminate X-values, however, there are control data volume and test time overhead issues. These issues become significant as the complexity and the density of the circuits increase. This paper proposes a method to eliminate X's by applying a scan slice granularity X-value correlation analysis. The proposed method exploits scan slice correlation analysis, determines unique control data for the scan slice groups sharing the same control data, and applies them for each scan slice. Hence, the volume of control data can be significantly reduced. The simulation results demonstrate that the proposed method achieves greater control data and test time reduction compared to the conventional methods, without loss of fault coverage.