A characterization of robust test-pairs for stuck-open faults

Tests for stuck-open faults in static CMOS circuits consist of a sequence of two input vectors. Such test-pairs may be invalidated by delays in the circuit. Test-pairs that are not invalidated by delays in the circuit are known as robust test-pairs. We present a six-valued logic system Ω = {0, 1, r, f, 0h, 1h}. We show how Ω differs from a number of other logic systems that have been proposed for test generation. This logic system abstracts the important aspects of the transition behavior of the circuit, on application of an input pair, that is necessary to characterize robust test-pairs for stuck-open faults. This characterization of robust test-pairs is used to derive:

1. an algorithm for determining if a given test-pair is a robust test-pair for a given stuck-open fault or not; and
2. a simplified algorithm for computing a robust test-pair for a stuck-open fault. The resulting algorithm for computing robust tests for stuck-open faults can be implemented by minor modifications to test generation algorithms for stuck-at faults.

     

A neural network algorithm for testing stuck-open faults in CMOS combinational circuits

In this article, an automatic test pattern generation technique using neural network models for stuck-open faults in CMOS combinational circuits is presented. For a gate level fault model of stuck-open faults in CMOS circuits, SR(slow-rise) and SF(slow-fall) gate transition faults we develop a neural network representation. A neural network computation technique for generating robust test patterns for stuck-open faults is given. The main result is extending previous efforts in stuck-at test pattern generation to stuck-open test pattern generation using neural network models. A second result is an extension of the technique to robust test pattern generation.     

Symbolic fault modelling of MOS combinational circuits

This paper presents a new method for fault modelling of MOS combinational circuits at the transistor level. Every transistor is replaced with a conductance controlled by the gate logic value. The specific advantage of the method is use of a symbolic simulator for circuit function extraction. This function is referred as Transistor Logic Conductance Function (TLCF). Starting from a known TLCF, a simple set of rules is used for output state determination. The method is suitable for multiple fault model generation thanks to the fact that only one symbolic analysis of a circuit is sufficient for modelling different stuck-open, stuck-short and stuck-at faults of a logic gate. Moreover, the method can deal also with bridging and cut faults. Finally, the application of the TLCF for test pattern generation is considered.     

An Exact approach for Complete Test Set Generation of Toffoli-Fredkin-Peres based Reversible Circuits

Reversible logic has gained interest of researchers worldwide for its ultra-low power and high speed computing abilities in the future quantum information processing. Testing of these circuits is important for ensuring high reliability of their operation. In this work, we propose an ATPG algorithm for reversible circuits using an exact approach to generate CTS (Complete Test Set) which can detect single stuck-at faults, multiple stuck-at faults, repeated gate fault, partial and complete missing gate faults which are very useful logical fault models for reversible logic to model any physical defect. Proposed algorithm can be used to test a reversible circuit designed with k-CNOT, Peres and Fredkin gates. Through extensive experiments, we have validated our proposed algorithm for several benchmark circuits and other circuits with family of reversible gates. This algorithm produces a minimal and complete test set while reducing test generation time as compared to existing state-of-the-art algorithms. A testing tool is developed satisfying the purpose of generating all possible CTS’s indicating the simulation time, number of levels and gates in the circuit. This paper also contributes to the detection and removal of redundant faults for optimal test set generation.     

Testing of multiple-output domino logic (MODL) CMOS circuits

Techniques for testing MODL circuits are presented. It is shown that, due to the greater observability of MODL circuits, their test sets can be considerably small than those derived for the conventional domino CMOS circuits. Tests for faults are derived from a comprehensive fault model which includes stuck-at, stuck-open, and stuck-on faults. Test sets for MODL circuits are inherently robust in the presence of circuit delays and timing skews at the inputs. They are also well-protected against the charge distribution problem. It is thus concluded that MODL is an attractive CMOS logic technique     

A switch-level test generation system for synchronous and asynchronous circuits

A switch-level test generation system for synchronous and asynchronous circuits has been developed in which a new algorithm for fully automatic switch-level test generation and an existing fault simulator have been integrated. For test generation, a switch-level circuit is modeled as a logic network that correctly models the behavior of the switch-level including bidirectionality, dynamic charge storage, and ratioed logic. The algorithm is able to generate tests for combinational and sequential circuits. BothnMOS and CMOS circuits can be modeled. In addition to the classical line stuck-at faults, the algorithm is able to handle stuck-open and stuck-closed faults on the transistors of the circuit.In synchronous circuits, the time-frame based algorithm uses asynchronous processing within each clock phase to achieve stability in the circuit and synchronous processing between clock phases to model the passage of time. In asynchronous circuits, the algorithm uses asynchronous processing to reach stability within and between modules. Unlike earlier time-frame based test generators for general sequential circuits, the test generator presented uses the monotonicity of the logic network to speed up the search for a solution. Results on benchmark circuits show that the test generator outperforms an existing switch-level test generator both in time and space requirements. The algorithm is adaptable to mixed-level test generation.     

Design of C-testable DCVS binary array dividers

Clocked differential cascode voltage switch (DCVS) circuits are dynamic CMOS circuits that have the advantage of being protected against test-set invalidation due to circuit delays and timing skews. The problem of testing nonrestoring and restoring DCVS binary array dividers is discussed. It is shown that a DCVS nonrestoring array divider can be made C-testable with only four or five vectors. These vectors detect all the detectable single stuck-at, stuck-open, and stuck-on faults in the circuit. The additional hardware required to achieve C-testability for an n×n nonrestoring array divider only consists of n-1 two-input XOR gates and one control input. It is also shown that a restoring DCVS binary array divider can be made C-testable with only six vectors, which also detect all the detectable single stuck-at, stuck-open, and stuck-on faults in the circuit. The hardware overhead required for the C-testable design of the n×n restoring array divider consists of n two-input XOR gates and one control input     

Stuck-open testable scan-based CMOS sequential circuits

A testing methodology for applying two-pattern tests for stuck-open faults in scan-testable CMOS sequential circuits is presented. This method requires shifting in only one pattern and requires no special latches in the scan chain. Sufficient conditions for robust testability of all single field-effect transistor (FET) stuck-open faults and design techniques for robustly scan-testable CMOS sequential circuits are presented. This technique leads to realizations with at most two additional inputs and some additional FET's in the first-level gates     

高效容错可逆的汉明码编码和检测电路

为了检验传输过程中数据的可靠性,设计了容错可逆的汉明码电路。提出了一种新型的可逆逻辑门（FVG）,它是一种四变量奇偶保持门能容错,并且完成了FVG门等价的量子实现。利用FVG 门和现有的容错可逆门,实现了汉明码编码电路和检测电路。以(7,4)汉明码设计为实例,根据量子代价和延迟对其进行性能评估,结果证明该电路比现有电路的性能提高10% ? 20%,仿真实验结果显示,电路逻辑结构正确,性能可靠。     

The effects of transistor source-to-gate bridging faults in complexCMOS gates

A study of the effect of gate-to-source bridging faults in the pull-up section of a complex CMOS gate is presented. The manifestation of these faults depends on the resistance value of the connection causing the bridging. It is shown that such faults manifest themselves either as stuck-at or stuck-open faults and can be detected by tests for stuck-at and stuck-open faults generated for the equivalent logic current. It is observed that for transistor channel lengths larger than 1 μm there exists a range of values of the bridging resistance for which the fault behaves as a pseudo-stuck-open fault     

Energy minimization and design for testability

The problem of fault detection in general combinational circuits is NP-complete. The only previous result on identifying easily testable circuits is due to Fujiwara who gave a polynomial time algorithm for detecting any single stuck fault inK-bounded circuits. Such circuits may only contain logic blocks with no more thanK input lines and the blocks are so connected that there is no reconvergent fanout among them. We introduce a new class of combinational circuits called the (k, K)-circuits and present a polynomial time algorithm to detect any single or multiple stuck fault in such circuits. We represent the circuit as an undirected graphG with a vertex for each gate and an edge between a pair of vertices whenever the corresponding gates have a connection. For a (k, K)-circuit,G is a subgraph of ak-tree, which, by definition, cannot have a clique of size greater thank+1. Basically, this is a restriction on gate interconnections rather than on the function of gates comprising the circuit. The (k, K)-circuits are a generalization of Fujiwara'sK-bounded circuits. Using the bidirectional neural network model of the circuit and the energy function minimization formulation of the fault detection problem, we present a test generation algorithm for single and multiple faults in (k, K)-circuits. This polynomial time aggorithm minimizes the energy function by recursively eliminating the variables.     

Delay fault simulation of sequential circuits

This article proposes a 7-valued logic appropriate for test generation and fault simulation, in the area of robust tests for gate delay faults, and a straightforward simulation strategy for sequential circuits. It is shown that a purely qualitative logic of robust testing is inadequate for circuits with edge-triggered flip-flops. The relation between the 7-valued logic and the similar logic proposed before by Smith, Schulz et al., and Lin and Reddy are discussed.     

Highly testable design of BiCMOS logic circuits

Most of the work reported in the literature to date on the testability of BiCMOS circuits has concentrated on fault characterization and the need for a suitable testing method that can address the peculiarities of BiCMOS circuits. The problem of adequately testing large BiCMOS logic networks remains open and complex. In this paper, we introduce a new design for testability technique for BiCMOS logic gates that results in highly testable BiCMOS logic circuits. The proposed design incorporates two features: a test charge/discharge path and built-in current sensing (BICS). The test charge/discharge path is activated only during testing and facilitates the testing of stuck-open faults using single test vectors. BICS facilitates testing of faults that cause excessive IDDQ. HSPICE simulation results show that the proposed design can detect stuck-open faults at a test speed of 10 MHz. Faults causing excessive IDDQ are detected by BICS with a detection time of 1 ns and a settling time of 2 ns. Impact of the proposed design on normal operation is minimal. The increase in propagation delay in normal operation is less than 3%. This compares very favorably with CMOS BICS reported in the literature, where the propagation delay increase was 20%, 14.4% respectively. The increase in the area is less than 15%     

On the design robustness of threshold logic gates using multi-inputfloating gate MOS transistors

In this paper, the design robustness of logic circuits implemented as threshold logic gates with multi-input floating gate transistors is analyzed. The parameter variations of the basic components, namely the coupling capacitances of the floating gate MOSFETs and the sensing circuits for obtaining full logic levels, are investigated separately using appropriate array test structures. It is found that the dominant mismatch originates from the input offset voltage variations of the sensing circuits. Methods are presented for estimating the yield of a given logic circuit from the measured parameter distributions. The estimations are verified with measured data of a multiplier cell and of the encoding logic in a parallel fingerprint sensor architecture. Considerations are given for robust design of circuits based on threshold logic gates that use floating gate transistors     

Testable Designs of Multiple Precharged Domino Circuits

Domino CMOS circuits are an option for speeding up critical units. An inherent problem of Domino logic is that under specific input conditions the charge redistribution between parasitic capacitances at internal nodes of a circuit can violate the noise margins and cause erroneous responses at the output. The dominant solution to this problem is the multiple precharging of the gate's internal nodes. However, the added precharge transistors are not testable for stuck-open faults. Undetectable stuck-open faults at these transistors may cause noise margins reduction and consequently may affect the reliability of the circuit since its operation in the field will be sensitive to environmental factors such as noise. In this paper, we propose new multiple precharging design schemes that enhance Domino circuits' testability with respect to transistor stuck-open and stuck-on faults     

Fault detection for multiple-valued logic circuits with fanout-free

The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits with n primary inputs is not more than n + 1, for linear tree circuits is two, and for multiplication modulo circuits is two if n is an odd number or if n is an even number and m > 3, where the optimal test set of a circuit has minimal number of test vectors. Secondly, it is indicated that the cardinality of optimal multiple fault test set for linear tree circuits with n primary inputs is 1 + [n/(m - 1)], for multiplication modulo circuits is n + 1, for fanout-free circuits that consist of 2-input linear tree circuits and 2-input multiplication modulo circuits is not greater than n+ 1, where [x] denotes the smallest integer greater than or equal to x. Finally, the single fault location approaches of linear tree circuits and multiplication modulo circuits are presented, and all faults in th     

Differential current switch logic: a low power DCVS logic family

Differential current switch logic (DCSL), a new logic family for implementing clocked CMOS circuits, has been developed. DCSL is in principle a clocked differential cascode voltage switch logic circuit (DCVS). The circuit topology outlines a generic method for reducing internal node swings in clocked DCVS logic circuits. In comparison to other forms of clocked DCVS, DCSL achieves better performance both in terms of power and speed by restricting internal voltage swings in the NMOS tree. DCSL circuits are capable of implementing high complexity high fan-in gates without compromising gate delay. Automatic lock-out of inputs on completion of evaluation is a novel feature of the circuit. Three forms of DCSL circuits have been developed with varying benefits in speed and power. SPICE simulations of circuits designed using the 1.2 μm MOSIS SCMOS process indicate a factor of two improvement in speed and power over comparable DCVS gates for moderate tree heights     

Dynamic effects in the detection of bridging faults in CMOS ICs

Dynamic effects in the detection of bridging faults in CMOS circuits are taken into account showing that a test vector designed to detect a bridging may be invalidated because of the increased propagation delay of the faulty signal. To overcome this problem, it is shown that a sequence of two test vectors < T ₀, T ₁ >, in which the second can detect a bridging fault as a steady error, can detect the fault independently of additional propagation delays if T₀ initializes the faulty signal to a logic value different from the fault-free one produced by T ₁. This technique can be conveniently used both in test generation and fault simulation. In addition, it is shown how any fault simulator able to deal with FCMOS circuits can be modified to evaluate the impact of test invalidation on the fault coverage of bridging faults. For any test vector, this can be done by checking the state of the circuit produced by the previous test vector.     

FAULT DETECTION TEST SET FOR TESTABLE REALIZATIONS OF LOGIC FUNCTIONS WITH ESOP EXPRESSIONS

The circuit testable realization and its fault detection for logic functions with ESOP （EXOR-Sum-Of-Products） expressions are studied. First of all, for the testable realization by using XOR gate cascade, a test set with 2n ＋ m ＋ 1 vectors for the detections of AND bridging faults and a test set with 2n ＋ m vectors for the detections of OR bridging faults are presented. Secondly, for the testable realization by using ）（OR gate tree, a test set with 2n ＋ m vectors for the detections of AND bridging faults and a test set with 3n ＋ m ＋ 1 vectors for the detections of OR bridging faults are presented. Finally, a single fault test set with n ＋ 5 vectors for the XOR gate tree realization is presented. Where n is the number of input variables and m is the number of product terms in a logic function.     

Generation and evaluation of current and logic tests for switch-level sequential circuits

This article presents an approach to developing high quality tests for switch-level circuits using both current and logic test generation algorithms. Faults that are aborted or undetectable by logic tests may be detected by current tests, or vice versa. An efficient switch level test generation algorithm for generating current and logic tests is introduced. Clear definitions for analyzing the effectiveness of the joint test generation approach are derived. Experimental results are presented for demonstrating high coverage of stuck-at, stuck-on, and stuck-open faults for switch level circuits when both current and logic tests are used.This is expanded version of the work originally presented at the 1991 International Test Conference.