Testing content-addressable memories using functional fault models and march-like algorithms

Abstract

Functional tests for content-addressable memories (CAM's) are presented in this paper. In addition to several traditional functional fault models for RAM's, we also consider the fault models based on physical defects, such as shorts between two circuit nodes and transistor stuck-on and stuck open faults. Accordingly, several functional fault models are proposed. In order to make our approach suited to various application-specific CAM's, we propose tests which require only three fundamental types of operation (i.e., write, erase, and compare), and the test results can be observed entirely from the single-bit Hit output. A complete, compact test is also proposed, which has low complexity and is suitable for modern high-density and large-capacity CAMs-it requires only 2N+3w+2 compare operations and 8N write operations to cover the functional fault models discussed, where N is the number of words and w is the word length.