Testing Comparison Faults of Ternary Content Addressable Memories with Asymmetric Cells

Abstract

Ternary content addressable memory (TCAM) is one key component in the dedicated hardware modulars for high-performance networking applications. Symmetric and asymmetric cells are two widely used cell structures in TCAMs. An asymmetric cell consists of a binary content addressable memory (BCAM) bit and a mask bit. This paper proposes two march-like test algorithms, TH it an TPAE, to cover the comparison faults of the BCAM cell and the comparison logic faults of the masking cell. Tan requires IN Write operations and (3N+2B) Compare operations to cover the comparison faults of an NtimesB-bit TCAM with Hit output only. TPAE requires 4N Write operations and (3N+2B) Compare operations to cover the comparison faults of an NtimesB-bit TCAM with priority address encoder (PAE) output.