Testability Measures Research Articles

Exact probabilistic testability measures for multi-output circuits

The computation of probabilistic testability measures has become increasingly important and some methods have been proposed, although the exact solution of the problem is NP-hard. An exact analytical method for singleoutput combinational circuits is extended to deal with multi-output circuits. Such circuits are reduced to singleoutput ones by introducing a dummy gate, the “X-gate,” and applying to the resulting graph the analysis based on supergates.

Germination characteristics in tropical provenances of Allocasuarina littoralis and A. torulosa

Germination of tropical provenances of Allocasuarina littoralis (Salisb.) L. Johnson and A. torulosa (Ait.) L. Johnson as affected by time of seed collection, light, temperature and storage conditions were examined. Changes in viability with seed development, as indicated by colour, were described. As seed colour darkened, viability increased, then levelled off or declined. The germination level of each provenance was found to be constant between 15 and 35°C, but germination rate reached an optimum between 25 and 35°C. Greater variation in germination rate was found in provenances of A. littoralis and of A. torulosa, with germination being delayed by up to 11.8 days in A. littoralis in the absence of light. Seed of both species was stored for 6 months at a range of temperatures and humidities without significant effect on germination level. Median germination time is recommended as a statistically testable measure of germination rate. Guidelines are given for handling seed for germination with respect to tropical agroforestry programmes.

Built-in self-test of the Macrolan chip

The implementation of self-test in the medium access controller chip for Macrolan, a fibre-optic, local area network, is described. The test style for 80% of the chip's combinational logic is quasiexhaustive testing. This approach, despite its apparent inefficiency in terms of the number of patterns used, gives considerable flexibility to the designer in arranging linear-feedback shift registers and so is easier to implement than some other techniques. The chip also uses a form of random-pattern test, not normally considered for memory testing, instead of a specialized pattern generator. Built-in self-test was implemented without using fault simulation or approximate testability measures. >

Testability analysis in a VLSI high-level synthesis system

This paper deals with the problem of defining testability measures for register-transfer level designs in order to incorporate them into the high-level synthesis system of VLSI circuits. First, a design representation and its observability and controllability measures are defined. Second, an algorithm for testability analysis is described. Third, some discussion about how the testability measures can be used to influence the synthesis process is given. Finally, some practical impact and applications of the presented approach are also indicated.

Measures of testability as a basis for quality assurance

Program testing is the most used technique for analytical quality assurance. A lot of time and effort is devoted to this task during the software lifecycle, and it would be useful to have a means for estimating this testing effort. Such estimates could be used, on one hand, for guiding construction and, on the other, to help organise the development process and testing. Thus the effort needed for testing is an important quality attribute of a program; they call it its testability. They argue that a relevant program characteristic contributing to testability is the number of test cases needed for satisfying a given test strategy. They show how this can be measured for glass (white) box testing strategies based on control flow. In this case, one can use structural measures defined on control flowgraphs which can be derived from the source code. In doing so, two well researched areas of software engineering testing strategies and structural metrication are brought together.< >

Measures of testability for automatic diagnostic systems : Nael A. E. Aly and Adel A. Aly. IEEE Trans. Reliab.37(5), 531 (December 1988)

Measures of testability for automatic diagnostic systems : Nael A. E. Aly and Adel A. Aly. IEEE Trans. Reliab.37(5), 531 (December 1988)

DYTEST: a self-learning algorithm using dynamic testability measures to accelerate test generation

A self-learning algorithm called DYTEST, which uses a dynamic testability measure (DTM) to accelerate test generation, is presented. DYTEST's DTM guides the choice of a potential main sensitizing path during test generation. A full-logic value label backward implication creates estimates of logic values for the primary inputs. Dependent and k-limited backtracks are used to further reduce the number of backtracks. >

Experimental evaluation of testability measures for test generation (logic circuits)

The results of an extensive study of five existing testability measures when used to aid heuristics for automatic test pattern generation algorithms are presented. Each measure was evaluated using over 60000 faults in circuits of varying size and complexity. The performance of these measures was rated using several different criteria. Based on these results the performance of a composite test generation strategy that uses multiple guidance heuristics was evaluated. The results indicate that this strategy not only provides better fault coverage but also reduces the average time taken to generate a test or determine that a given fault is undetectable. >

Influence of guiding testability measure on number of backtracks of ATPG program

A major problem, in accelerating an algorithm for test generation, is how to reduce the number of backtracks. The paper considers different measures of controllability and observability, and compares the number of backtracks obtained on large combinational circuits. The paper proposes a new controllability measure which is, on average, more efficient than the others. >

Ambiguity groups and testability

An efficient method has been developed for determining component ambiguity groups which arise in analog circuit testing. The method makes use of the sensitivity model of the circuit. The ambiguity groupings are shown to depend on the test points selected and the measurement accuracy and are therefore a useful tool for determining where to add or delete test points. The concept of ambiguity groups can be used to refine the testability measure of a circuit. An example that demonstrates the effects of ambiguity groups on parameter estimation and performance prediction is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The reliability of approximate testability measures

Techniques for gauging the accuracy of approximate testability measures that estimate the random-pattern testability of gate-level faults in designs with combinational logic are considered. The measures examined are overall fault-exposure distribution, high coverage, and fault grading. Sampling techniques are compared with the Stafan and Protest approximate testability measures. For random-pattern testing, it is clear that state-of-the-art testability measures like Stafan and Protest do provide some information about the testability of single faults or complete designs, but this information is not accurate; in many areas of use they cannot compete with carefully chosen sampling techniques. The three techniques described here are applicable to testing strategies other than the random-pattern testing of stuck-at faults; they are equally useful in a weighted random-pattern testing environment, for example.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Dynamic testability measures for ATPG

Two automatic test pattern generation (ATPG) algorithms, PODEM and FAN, use heuristics that rely on testability measures (TMs). The use of random-pattern (probabilistic) TMs in these heuristics has already been proposed and investigated. The types of TMs proposed for such use are static. Static TMs (STMs) become increasingly unjustifiable as the search for a test pattern progresses. Dynamic TMs (DTMs) are introduced as a method to overcome the deficiency in the quality of STMs while still observing linear time and storage constraints. Based on results from several experiments, test-set generation strategy is devised that utilizes the advantages of both STMs and DTMs. From the experiments performed on benchmark circuits, compared to the strategy wherein only STMs are used to attain a given fault coverage, the proposed strategy requires considerably less CPU time to obtain a test set which attains the same fault coverage.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reconvergent-fanout-oriented testability measure

This paper describes the theory and implementation of a testability measure program called RFOTM. It is suggested that the real difficulty in test generation should be reflected in testability measure. We analyse the behavior of fanout and reconvergent fanout which cause inconsistency in generating tests. A classification of fanouts is given and a class of fanouts which behaves like fanout-free lines is described. Based on this observation, the new measure is developed with emphasis on the influence of fanout and reconvergent fanout, and is shown with more accurate prediction for testing difficulty and acceptable computing complexity.

Measures of testability for automatic diagnostic systems

Evaluation models of automatic diagnostic systems are investigated taking into consideration their imperfections such as failure to diagnose, incorrect isolation, false alarms, and inability to duplicate. Three measures of effectiveness are developed that enable the decision-maker to assess accurately the real capability of the diagnostic system and to evaluate and compare the performances of alternative automatic diagnostic systems based on their mean life-cycle cost. Analytic procedures for using these measures are developed, and an example is presented. It is concluded that the capability and performance of automatic diagnostic systems can be assessed using three measures of effectiveness; false removal, failure to diagnose, and false alarm correction. The three measures can be used to predict the mean life-cycle cost of automatic diagnostic systems, including the mean cost of imperfections of such systems. >

Test-point selection and testability measures via QR factorization of linear models

An efficient algorithm is presented for selecting test points for use in applications such as calibration and fault diagnosis of electronic networks. The algorithm, based on QR factorization of the circuit sensitivity matrix, minimizes the prediction or estimation errors which result from random measurement error. A definition of testability based on the concept of minimum estimation error is also introduced. Practical examples are given.

Algorithm to detect reconvergent fanouts in logic circuits

Testability measures have been advocated by many authors as aids in the designing and testing of logic circuits. These have been shown to be inaccurate for circuits which contain reconvergent fanouts. An algorithm is presented which will detect all sources of reconvergence in a circuit by processing a normal textual circuit description. As well as identifying all the gates at which reconvergence occurs, the reconvergent sites, the algorithm lists all the fanout nodes that reconverge at each of these sites. The automatic detection of reconvergence can be used for improving the testability analysis of circuits containing such fanouts. This algorithm is also being used as the basis of an analysis which identifies the undetectable faults in a circuit.

Multifrequency measurement of testability with application to large linear analog systems

With increasing electronic circuit complexity, assessing the testability features becomes a necessity during the design, implementation, and operational or maintenance phases of an analog system. A quantitative measure of testability, based on several multifrequency stimuli, is adopted which is able to handle multiple faults and may provide information also on the degree of complexity encountered in a specific test. An efficient and practical algorithm is proposed which is associated with the result of Sen and Saeks and has a well-defined interpretation even with a large number of circuit parameters liable to failure. The described technique is a basis for optimizing the number and allocation of the selected test points; furthermore, it may serve as an aid in functional partitioning of the same system to facilitate testing and/or reduce computational complexity. An application to a classical active filter is also given.

Fault diagnosis of analog circuits

In this paper, various fault location techniques in analog networks are described and compared. The emphasis is on the more recent developments in the subject. Four main approaches for fault location are addressed, examined, and illustrated using simple network examples. In particular, we consider the fault dictionary approach, the parameter identification approach, the fault verification approach, and the approximation approach. Theory and algorithms that are associated with these approaches are reviewed and problems of their practical application are identified. Associated with the fault dictionary approach we consider fault dictionary construction techniques, methods of optimum measurement selection, different fault isolation criteria, and efficient fault simulation techniques. Parameter identification techniques that either utilize linear or nonlinear systems of equations to identify all network elements are examined very thoroughly. Under fault verification techniques we discuss node-fault diagnosis, branch-fault diagnosis, subnetwork testability conditions as well as combinatorial techniques, the failure bound technique, and the network decomposition technique. For the approximation approach we consider probabilistic methods and optimization-based methods. The artificial intelligence technique and the different measures of testability are also considered. The main features of the techniques considered are summarized in a comparative table. An extensive, but not exhaustive, bibliography is provided.

A testability measure to improve algebraic test generation

The paper deals with testability measures of digital systems. Specifically, a new algorithm to evaluate testability measures for circuits described in terms of Boolean equations is presented, and its application to speed up (algebraic) test generation for sequential networks is discussed.

New measures of testability and test complexity for linear analog failure analysis

The failure analysis of analog electronic systems is characterized by numerous, difficult problems. Assessing the testability and test complexity of a given system is one such problem. In fact, robust, quantitative measures of these important features have not been available to the analog testing community. This paper introduces new measures for both testability and test complexity which: 1) are quantitative, 2) are capable of handling multiple faults, and 3) have a well-defined interpretation. These measures are based upon published results from optimal experiment designs as developed in the discipline of systems identification. Parameter testability is defined in terms of information (in the sense of Fisher) return, while test complexity is functionally related to the experiment time required to achieve specified accuracy with regard to the uncertain parameters of interest. Thus both of the new measures introduced depend, not only upon the specific system at hand, but also upon the experimental conditions used in performing the tests. The results of this approach lead to quantitative measures that have optimality features based upon the Cramer-Rao bound.