Testing ternary content addressable memories with active neighbourhood pattern-sensitive faults

With shrinking transistor sizes and growing transistor density, testing neighbourhood pattern-sensitive faults (NPSFs) is increasingly important for semiconductor memories. A test methodology for detecting active NPSFs (ANPSFs) and static NPSFs (SNPSFs) in ternary content addressable memories (TCAMs) is presented. March-like and two-group test methods are two commonly used testing techniques for NPSFs in random access memories. Because of the special TCAM cell structure, however, using a unique test algorithm with only either a March-like or a two-group test operations are not time-efficient. A test methodology that employs both March-based and two-group testing to cover 100% ANPSFs and SNPSFs in TCAMs is proposed. The total test complexity of the proposed test methodology is 156 N for an N x K-bit TCAM. No TCAM circuit modification is needed to support the proposed test methodology.