It is used for post manufacturing testing, not design testing. The total number of single and multiple stuckat faults in a circuit with k. Twinning fault main limit open line and neutral reversed mrlc man. The basic assumptions that characterize single stuckat fault model are2. Ee4301 fall 2004 examples stuckat fault examples problem 1. The model assumes one line or node in the digital circuit is stuck at logic high or logic low. For example, the most common fault model assumes singlestuck faults even though it is clear that this model does not accurately represent all actual physical failures. Many different physical defects may be modeled by the same logical stuck at fault.
Table 102 tests for stuck at faults in figure 104 normal gate inputs a b c d a b p c q r d s t u v w faults tested 0 1 0 1 0 1 0 0 0 1 1 0 1 1 0 1 a1 p1 c1 v1 f1. This chapter presents an easily testable cmos implementation of a combinational circuit based on esop expressions for detecting single stuck open faults. The total number of single and multiple stuckat faults in a circuit with k single fault sites is 3k1. A delay fault model for synchronous sequential circuits in this paper, we describe a new transition fault model for synchronous sequential circuits. Most of the work in diagnosis has been based on the classical single stuckat fault model. The other is to extend the basic diagnosis algorithm for the single stuckat fault model to other defect types 6, 7 or to multiple faults 8.
Testability challenges in any synthesis approach include complete fault e ciency and ease of test generation for a fault model. Fault models kit chair of dependable nano computing. Total number of single and multiple stuckat faults in circuit with k single fault sites 3k1 why taking about multiple sav faults ztests for single sav not necessarily sufficient for detecting multiple sav faults e single fault test can fail to detect target fault if another fault present masking of one fault by another rare. Test generation techniques have also been developed to generate test vectors to distinguish pairs of faults 79. Ssf is technology independent has been successfully used on ttl, ecl, cmos, etc.
Models curtain kinds of fabrication flaws that short circuit. Fault model stuckat model assume selected wires gate input or output are stuck at logic value 0 or 1 models curtain kinds of fabrication flaws that short circuit wires to ground or power, or broken wires that are floating wire w stuckat0. In this paper we introduce a method to calculate the cfm testability of a cellbased. Single stuck at fault single line stuck at fault the given line has a constant value 01 independent of other signal values in the circuit properties only one line is faulty the faulty line is permanently set to 0 or 1 the fault can be at an input or output of a gate simple logical model is independent of technology details. Pdf test generation for single and multiple stuckat faults of a. Testing for single faults will simultaneously test certain multiple faults too but not all multiple faults are tested.
A previously proposed method for diagnosing bridging faults using single stuckat dictionaries was applied only to small circuits, produced large and imprecise diagnoses, and did not take into account the. The vast majority of test tools are based on the single stuck at fault model. Testing of logic circuits fault model fault model fault model. How good are these test vectors for a variety of defects.
But the stuck open fault model covers the physical defects not covered by stuck at fault models. A logic stuckat 1 means when the line is applied a. This model is used because it has been found to be statistically correlated with defectfree circuits 14 single stuckat faults a fault is assumed to occur only on a single net. Xor circuit has 12 fault sites and 24 single stuckat faults c. Even when single stuckat fault does not accurately model some physical defects, the tests derived for logic faults are still valid for most defects. Diagnosis of realistic bridging faults with single stuckat. Many other faults bridging, stuckopen and multiple stuckat are largely covered by stuckat fault tests. Fault modeling electronic circuits mosfet free 30day.
Fault analysis example switch to the fault data tab, and select fault bus number 3 leave as bus fault, single line to ground click calculate the case will be solved first to make sure the analysis will be valid the fault analysis calculation is a linearized calculation about the operating point. Stuckat0 and stuckatl faults are denoted by abbreviations sa0 and sa1, respectively. The faulty line is permanently set to either 0 or 1. With a stuck at fault model you are applying a structural test approach. It assumes that a fault in a logic gate results in one of its inputs or the output is fixed at either a logic 0 stuckat0 or at logic 1 stuckat1. Pdf diagnosing realistic bridging faults with single stuck. Static faults, which give incorrect values at any speed and sensitized by performing only one operation. Gate arrays, standard cell, custom vlsi even when single stuckat fault does not accurately model some physical defects, the tests derived for logic faults are still valid for most defects. Fault models have the advantage of being a more tractable representation than physical failure modes, but risk the omission of vital effects on system operations. Precise failure analysis requires accurate fault diagnosis.
Xor circuit has 12 fault sites and 24 single stuck at faults faulty circuit value c 1 0. Stuckat fault examples problem 1 a b c d e f g h i s. Stuckat based diagnosis algorithms are often classi. Cell fault model cfm is a welladopted functional fault model used for cellbased circuits. Digital circuits and stuck at fault model accendo reliability. A signal, or gate output, is stuck at a 0 or 1 value, independent of the inputs to the circuit. Modeling the effects of physical defects on the logic function and timing. For digital logic single stuckat fault model offers best advantage of tools and experience. Stuckshort and delay faults and technologydependent faults require special tests. If a network contains logical redundancy, then not all faults are detectable 5. Such models can be used to predict the consequences of a given fault.
We represent the fault free value and the propagation bit. The most commonly used model is a single stuck at fault. Xor circuit has 12 fault sites and 24 single stuckat faults faulty circuit value c 1 0. The single stuck at fault has previously being used for modeling path delay faults 4. Stuck at fault models operate at the logic model of digital circuits. Enhancing diagnosis resolution for delay defects based. The other is to extend the basic diagnosis algorithm for the single stuck at fault model to other defect types 6, 7 or to multiple faults 8. Single stuck line is a fault model used in digital circuits. Figure 101 testing and and or gates for stuckat faults. Jan 10, 2014 single stuck at fault three properties define a single stuck at fault only one line is faulty the faulty line is permanently set to 0 or 1 the fault can be at an input or output of a gate. For example, the most common fault model assumes single stuck faults even though it is clear that this model does not accurately represent all actual physical failures.
Single stuckat fault three properties define a single stuckat fault only one line is faulty the faulty line is permanently set to 0 or 1 the fault can be at an input or output of a gate. Pdf single stuck line is a deficiency model utilized as a part of computerized circuits. Only one line is faulty the faulty line is permanently set to 0 or 1 the fault can be at an input or output of a gate. Fully testable circuit synthesis for delay and multiple stuck. However in 7 it is shown that simple extra gate errors could be rectified using only gate substitution error model. Nand gate has 3 fault sites and 6 single stuckat faults a b 1 1 z sa0 fault, sa1 fault. Multiple stuck at fault model analysis semantic scholar. A stuck open fault in a combinational circuit may induce a. Xor circuit has 12 fault sites and 24 single stuck at faults c. The total number of single and multiple stuck at faults in a. Fault dictionaries have commonly been used for fault diagnosis 6. I have done decoder but am stuck with sub circuits. Single stuckat fault model other fault models redundancy. Single stuck at tests cover a large percentage of multiple stuck at faults.
Section 4 a connection between fault models of shared robdd and single stuckat faults of. Switch stuck open, should be closed water sensed circuit open water sensed blower fault blower unable to run internal control fault blocked drain fault 59 should be present. Single stuckfault model ssf is the classical or standard fault model. The two level logic network of andor gates shown below has inputs a, b, c, d, e, f, g, h, i, an output s. This technique allows simulation and test generation for the modeled fault by any single fault simulator or test generator. Statistically, single fault tests cover a very large number of multiple faults. This model is used because it has been found to be statistically correlated with defectfree circuits 14 single stuck at faults a fault is assumed to occur only on a single net. Single stuckat fault three properties define a single stuckat fault only one line is faulty the faulty line is permanently set to 0 or 1 the fault can be at an input or output of a gate example. Fault modeling electrical engineering and computer science. Ee4301 fall 2004 examples stuck at fault examples problem 1. Fundamental algorithms for system modeling, analysis, and. The total number of single and multiple stuck at faults in a circuit with k single fault sites is 3k1. Stuckat fault the most common model used for logical faults is the single stuckat fault. Test generation and fault simulation for cell fault model.
Some definitions why modeling faults various fault models. Table 102 tests for stuckat faults in figure 104 normal gate inputs a b c d a b p c q r d s t u v w faults tested 0 1 0 1 0 1 0 0 0 1 1 0 1 1 0 1 a1 p1 c1 v1 f1. Ifa ineffective fault analysis stuckat fault model assumed, e. The vast majority of test tools are based on the single stuckat fault model. A single fault test can fail to detect the target fault if another fault is also present, however, such masking of one fault by another is rare.
In our experiment, the single stuck fault model isnt very accurate. In this paper we introduce a method to calculate the cfm testability of a cellbased circuit using any single stuckat. Proposition 1 under the single stuckat fault model a test set is complete if and only if each. Path delay fault pdf and multiple stuckat faultmsaf models uncover defects that are missed by the ssaf model. Single stuckat fault model other fault models redundancy and untestable faults fault equivalence and fault dominance method of boolean difference. In fault simulation we use a fault model which models physical faults that may occur in actual circuits. The single stuckat faultssaf model is a popular model which covers many defects but not all. The single stuckat fault has previously being used. The total number of single and multiple stuckat faults in a circuit with k single fault sites is 3 k1. Its usefulness results from the following attributes. Instead of testing all combination of 1s and 0s to a vlsi device, you will test with a reduced set of test vectors.
But the stuckopen fault model covers the physical defects not covered by stuckat fault models. A multiple fault is a simultaneous presence of several single faults. Single stuckat fault single line stuckat fault the given line has a constant value 01 independent of other signal values in the circuit properties only one line is faulty the faulty line is permanently set to 0 or 1 the fault can be at an input or output of a gate simple logical. In this paper we introduce a method to calculate the cfm testability of a cellbased circuit using any single stuck at. Most of the work in diagnosis has been based on the classical single stuck at fault model. The number of single stuckat faults is 2k a single fault test can fail to detect the target fault if another fault is also present however, such masking of one fault by another is rare. Since the ssf model was not accurate for 23 of the defective cuts, one might suppose that test sets generated using this inaccurate model would miss as many as 66% of the defective cuts. Single stuck fault model ssf is the classical or standard fault model. Single stuckat fault model other fault models redundancy and. I need some help here engineers on digital circuits. The results of applying ssf test sets with coverage. Ssf is technology independent s has been successfully used on ttl, ecl, cmos, etc. This technique allows simulation and test generation for the modeled fault by any singlefault simulator or test generator.
Despite of the wide adoption of cfm, no test tool is available for the estimation of cfm testability. Test generation and fault simulation for cell fault model using. Design error diagnosis in digital circuits with stuckat fault model. Many different physical defects may be modeled by the same logical stuckat fault. Activates the fault sa0 on line g by applying a logic. Single stuckat tests cover a large percentage of multiple stuckat faults.
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