On Fault Modeling and Testing of Content-addressable Memories

Associative or content addressable memories can be used for many computing applications. This paper discusses fault modeling for the content addressable memory (CAM) chips. Detailed examination of a single CAM cell is presented. A functional fault model for a CAM architecture executing exact match derived from the single cell model is presented. An efficient testing strategy can be derived using the proposed fault mode

Faulty Behavior of Storage Elements and Its Effects on Sequential Circuits

It is often assumed that the faults in storage elements (SEs) can be modeled as output/input stuck-at faults of the element. They are implicitly considered equivalent to the stuck-at faults in the combinational logic surrounding the SE cells. Transistor-level faults in common SEs are examined here. A more accurate higher level fault model for elementary SEs that better represents the physical failures is presented. It is shown that a minimal (stuck-at) model may be adequate if only modest fault coverage is desired. The enhanced model includes some common fault behaviors of SEs that are not covered by the minimal fault model. These include data-feedthrough and clock-feedthrough behaviors, as well as problems with logic level retention. Fault models for complex SE cells can be obtained without a significant loss of information about the structure of the circuit. The detectability of feedthrough faults is considered

Data-Feedthrough Faults in Circuits using Unclocked Storage Elements

Some faults in storage elements (SEs) do not manifest as stuck-at-0/1 faults. These include data-feedthrough faults that cause the SE cell to exhibit combinational behaviour. The authors investigate the implications of such faults on the behaviour of circuits using unclocked SEs. It is shown that effects of data-feedthrough faults at the behavioural level are different from those due to stuck-at faults, and therefore tests generated for the latter may be inadequat

A novel ultrasound technique to detect early chronic kidney disease [version 2; referees: 2 approved]

Chronic kidney disease (CKD) of unknown etiology is recognized as a major public health challenge and a leading cause of morbidity and mortality in the dry zone in Sri Lanka. CKD is asymptomatic and are diagnosed only in late stages. Evidence points to strong correlation between progression of CKD and kidney fibrosis. Several biochemical markers of renal fibrosis have been associated with progression of CKD. However, no marker is able to predict CKD consistently and accurately before being detected with traditional clinical tests (serum creatinine, and cystatin C, urine albumin or protein, and ultrasound scanning). In this paper, we hypothesize that fibrosis in the kidney, and therefore the severity of the disease, is reflected in the frequency spectrum of the scattered ultrasound from the kidney. We present a design of a simple ultrasound system, and a set of clinical and laboratory studies to identify spectral characteristics of the scattered ultrasound wave from the kidney that correlates with CKD. We believe that spectral parameters identified in these studies can be used to detect and stratify CKD at an earlier stage than what is possible with current markers of CKD

Antirandom Testing: Beyond Random Testing

Random testing is a well known concept that requires that each test is selected randomly regardless of the test previously applied. In actual practice it takes the form of pseudo-random testing, where each test pattern is a shifted version of the previous one with one new bit added. This paper introduces the concept of antirandom testing. In this testing strategy each test applied is chosen such that its total distance from all previous tests is maximum. This spans the test vector space to the maximum extent possible for a given number of vectors. This strategy results in a higher fault coverage when the number of vectors that are applied is limited. Algorithm for generating antirandom tests is presented. A Reed-Solomon code based test set is also introduced that results in test vectors with antirandom characteristics. Results comparing the different test strategies on ISCAS benchmarks show these strategies to be very effective when a high fault coverage needs to be achieved with a lim..

On Growth of Parallelism within Routers and Its Impact on Packet Reordering 1

Abstract — The network link speeds increase at a higher rate compared to processing speeds. This coupled with the increase in size of router tables demand higher levels of parallelism within router hardware. However, such parallelism introduces unintended consequences that potentially may negate some of the performance gains provided by the improved technology. The growth trends of computing speeds, link speeds, and routing table sizes are used to evaluate one such consequence, packet reordering within routers. Results presented show the trends related to the degree of hardware parallelism and packet reordering I