Testing content addressable memories with physical fault models
Lin Ma, Xu Yang, Zhong Shiqiang, and Chen Yunji · Journal of Semiconductors · 2009
Content addressable memory (CAM) is widely used and its tests mostly use functional fault models. However, functional fault models cannot describe some physical faults exactly. This paper introduces physical fault models for write-only CAM. Two test algorithms which can cover 100% targeted physical faults are also proposed. The algorithm for a CAM module with N -bit match output signal needs only 2 N +2 L +4 comparison operations and 5 N writing operations, where N is the number of words and L is the word length. The algorithm for a HIT-signal-only CAM module uses 2 N +2 L +5 comparison operations and 8 N writing operations. Compared to previous work, the proposed algorithms can test more physical faults with a few more operations. An experiment on a test chip shows the effectiveness and efficiency of the proposed physical fault models and algorithms.