Built-In Test Sequence Generation for Synchronous Sequential Circuits Based on Loading and Expansion of Test Subsequences

We describe an on-chip test generation scheme for synchronous sequential circuits that allows at-speed testing of such circuits. The proposed scheme is based on loading of (short) input sequences into an on-chip memory, and expansion of these sequences on-chip into test sequences. Complete coverage of modeled faults is achieved by basing the selection of the loaded sequences on a deterministic test sequence T 0, and ensuring that every fault detected by T 0 is detected by the expanded version of at least one loaded sequence. Experimental results presented for benchmark circuits show that the length of the sequence that needs to be stored at any time is on the average 10 % of the length of T 0, and that the total length of all the loaded sequences is on the average 46 % of the length of T 0. 1

An Efficient Test Relaxation Technique for Synchronous Sequential Circuits

Testing systems-on-a-chip (SOC) involves applying huge amounts of test data, which is stored in the tester memory and then transferred to the circuit under test (CUT) during test application. Therefore, practical techniques, such as test compression and compaction, are required to reduce the amount of test data in order to reduce both the total testing time and the memory requirements for the tester. Test-set relaxation can improve the efficiency of both test compression and test compaction. In addition, the relaxation process can identify selfinitializing test sequences for synchronous sequential circuits. In this paper, we propose an efficient test relaxation technique for synchronous sequential circuits that maximizes the number of unspecified bits while maintaining the same fault coverage as the original test set

ON EFFICIENT EXTRACTION OF PARTIALLY SPECIFIED TEST SETS FOR SYNCHRONOUS SEQUENTIAL CIRCUITS

Testing systems-on-a-chip (SOC) involves applying huge amounts of test data, which is stored in the tester memory and then transferred to the circuit under test (CUT) during test application. Therefore, practical techniques, such as test compression and compaction, are required to reduce the amount of test data in order to reduce both the total testing time and the memory requirements for the tester. Relaxing test sequences, i.e. extracting partially specified test sequences, can improve the efficiency of both test compression and test compaction. In this paper, we propose an efficient test relaxation technique for synchronous sequential circuits that maximizes the number of unspecified bits while maintaining the same fault coverage as the original test set

The Fifth NASA Symposium on VLSI Design

The fifth annual NASA Symposium on VLSI Design had 13 sessions including Radiation Effects, Architectures, Mixed Signal, Design Techniques, Fault Testing, Synthesis, Signal Processing, and other Featured Presentations. The symposium provides insights into developments in VLSI and digital systems which can be used to increase data systems performance. The presentations share insights into next generation advances that will serve as a basis for future VLSI design

Static Compaction of Test Sequences for Synchronous Sequential Circuits

Today, VLSI design has progressed to a stage where it needs to incorporate methods of testing circuits. The Automatic Test Pattern Generation (ATPG) is a very attractive method and feasible on almost any combinational and sequential circuit. Currently available automatic test pattern generators (ATPGs) generate test sets that may be excessively long. Because a cost of testing depends on the test length. compaction techniques have been used to reduce that length. The motivation for studying test compaction is twofold. Firstly, by reducing the test sequence length. the memory requirements during the test application and the test application time are reduced. Secondly, the extent of test compaction possible for deterministic test sequences indicates that test pattern generators spend a significant amount of time generating test vectors that are not necessary. The compacted test sequences provide a target for more efficient deterministic test generators. Two types of compaction techniques exist: dynamic and static. The dynamic test sequence compaction performs compaction concurrently with the test generation process and often requires modification of the test generator. The static test sequence compaction is done in a post-processing step to the test generation and is independent of the test generation algorithm and process. In the thesis, a new idea for static compaction of test sequences for synchronous sequential circuits has been proposed. Our new method - SUSEM (Set Up Sequence Elimination Method) uses the circuit state information to eliminate some setup sequences for the target faults and consequently reduce the test sequence length. The technique has been used for the test sequences generated by HITEC test generator. ISCAS89 benchmark circuits were used in our experiments, for some circuits which have a large number of target faults and relatively small number of flip-flops, the very significant compactions have been obtained. The more important is that this method can be used to improve the test generation procedure unlike most static compaction methods which blindly or randomly remove parts of test vectors and cannot be used to improve the test generators

Automatic test pattern generation for asynchronous circuits

The testability of integrated circuits becomes worse with transistor dimensions reaching nanometer scales. Testing, the process of ensuring that circuits are fabricated without defects, becomes inevitably part of the design process; a technique called design for test (DFT). Asynchronous circuits have a number of desirable properties making them suitable for the challenges posed by modern technologies, but are severely limited by the unavailability of EDA tools for DFT and automatic test-pattern generation (ATPG). This thesis is motivated towards developing test generation methodologies for asynchronous circuits. In total four methods were developed which are aimed at two different fault models: stuck-at faults at the basic logic gate level and transistor-level faults. The methods were evaluated using a set of benchmark circuits and compared favorably to previously published work. First, ABALLAST is a partial-scan DFT method adapting the well-known BALLAST technique for asynchronous circuits where balanced structures are used to guide the selection of the state-holding elements that will be scanned. The test inputs are automatically provided by a novel test pattern generator, which uses time frame unrolling to deal with the remaining, non-scanned sequential C-elements. The second method, called AGLOB, uses algorithms from strongly-connected components in graph graph theory as a method for finding the optimal position of breaking the loops in the asynchronous circuit and adding scan registers. The corresponding ATPG method converts cyclic circuits into acyclic for which standard tools can provide test patterns. These patterns are then automatically converted for use in the original cyclic circuits. The third method, ASCP, employs a new cycle enumeration method to find the loops present in a circuit. Enumerated cycles are then processed using an efficient set covering heuristic to select the scan elements for the circuit to be tested.Applying these methods to the benchmark circuits shows an improvement in fault coverage compared to previous work, which, for some circuits, was substantial. As no single method consistently outperforms the others in all benchmarks, they are all valuable as a designer’s suite of tools for testing. Moreover, since they are all scan-based, they are compatible and thus can be simultaneously used in different parts of a larger circuit. In the final method, ATRANTE, the main motivation of developing ATPG is supplemented by transistor level test generation. It is developed for asynchronous circuits designed using a State Transition Graph (STG) as their specification. The transistor-level circuit faults are efficiently mapped onto faults that modify the original STG. For each potential STG fault, the ATPG tool provides a sequence of test vectors that expose the difference in behavior to the output ports. The fault coverage obtained was 52-72 % higher than the coverage obtained using the gate level tests. Overall, four different design for test (DFT) methods for automatic test pattern generation (ATPG) for asynchronous circuits at both gate and transistor level were introduced in this thesis. A circuit extraction method for representing the asynchronous circuits at a higher level of abstraction was also implemented. Developing new methods for the test generation of asynchronous circuits in this thesis facilitates the test generation for asynchronous designs using the CAD tools available for testing the synchronous designs. Lessons learned and the research questions raised due to this work will impact the future work to probe the possibilities of developing robust CAD tools for testing the future asynchronous designs

論理シミュレーションとハードウェア記述言語に関する研究

京都大学0048新制・論文博士工学博士乙第7496号論工博第2471号新制||工||842(附属図書館)UT51-91-E273(主査)教授 矢島 脩三, 教授 津田 孝夫, 教授 田丸 啓吉学位規則第5条第2項該当Kyoto UniversityDFA