Issue No. 10 - October (2000 vol. 49)
ISSN: 0018-9340
pp: 1054-1063
ABSTRACT
<p><b>Abstract</b>—This paper presents an extensive model and algorithms for detecting faults in SRAM-based dual-port and uni-port CAMs (Content Addressable Memories). This model is based on analyzing the functionalities of a cell of an SRAM-based CAM and dividing it into two parts (storage and comparison parts). It is shown that faults can affect one or both parts. While storage faults can be detected using a traditional test algorithm (such as the March C), faults affecting the comparison part of the cell require a substantially different approach. A complete characterization of these faults is presented; by analyzing the structure of the cell in the dual and uni-port configurations, physical faults (such as stuck-at, stuck-open, stuck-on, bridge) in lines and transistors can be mapped to three functional fault sets by the execution of the comparison operation. Two new detection algorithms (directly compatible with the word-oriented March C algorithm, as widely used in existing commercial tools) are proposed; 100 percent coverage is achieved. The first algorithm (Concurrent Detection Algorithm or CDA) employs concurrent operations for testing a dual-port CAM; the second algorithm (Non Concurrent Detection Algorithm or NCDA) uses nonconcurrent operations and can be used for testing dual-port as well as uni-port CAMs. CDA requires eight passes and (<tmath>$10N+2L$</tmath>) tests, where <tmath>$N$</tmath> is the number of words of the CAM and <tmath>$L$</tmath> is the width of a word. NCDA requires eight passes, too, but (<tmath>$12N+2L$</tmath>) tests. The number of tests required by CDA (and NCDA, too) is significantly less than required by existing algorithms.</p>
INDEX TERMS
Content addressable memory, memory testing, fault detection, March C algorithm, fault modeling.
CITATION
M. Puri, S. Irrinki, F. Lombardi, J. Zhao, "Testing SRAM-Based Content Addressable Memories", IEEE Transactions on Computers, vol. 49, no. , pp. 1054-1063, October 2000, doi:10.1109/12.888041