A Self-Reconfigurable Platform for Built-In Self-Test Applications

This paper discusses the novel idea of testing digital circuits using run-time reconfigurable techniques, in order to minimize circuit area, as well as test generation and application time. The idea revolves around the dynamic partial reconfiguration of circuits under test, in order to inject stuck-at faults at different locations of the circuit, and uncover both detectable and undetectable faults. The paper presents a practical implementation of run-time reconfigurable methodologies using an actual reconfigurable device, the Xilinx Virtex-II, in the development of a test architecture.

The technological revolution witnessed by the telecommunications industry is leading to the development of new applications, products, and protocols, which in turn solicits widely accessible, highly reliable, and high-quality networks. To meet the stringent quality and reliability requirements of today's complex communication networks, efficient test methodologies are necessary at all levels (system, board, circuit, etc.). Conventional test methodologies are being constantly challenged by ever-increasing speed and circuit size, which results in high costs associated with test hardware, test generation, and test application time. Built-in self-test offers a test methodology where the test functions are embedded into the circuit itself. The advantages of using BIST for complex telecommunication systems are numerous. Reduced test development time, low test application time, eliminating the need for very-high-speed hardware testers, provision for at-speed tests, in-field test capability, and high fault coverage are some of them. In this article we present a tutorial on the BIST methodology targeted mainly toward telecommunication systems, the test structures necessary for its incorporation both at the circuit and system levels, and test implementation at the higher levels of design abstraction.

Three issues that are dominating test research today are test application time, test data volume and test power. Researchers have focused on these issues mostly considering the popular serial scan architecture for its relatively low hardware overhead while ignoring the fact that exponential drop in hardware cost offers opportunities for implementing a test architecture that previously may have been unacceptable. This paper takes such a paradigm shift into account and studies the simultaneous solution of all three problems of serial scan by making use of progressive random access scan test architecture. This architecture only increases the hardware cost marginally while providing marked improvements for the three issues. This paper explains the test architecture and then develops a test generation methodology which reduces the test application time by nearly 75%, test data volume by 50% for the benchmark circuits. Above all, the architecture is inherently so efficient that it reduces the test power by nearly 99% or more of the test power consumption compared to serial scan

Single input change (SIC) sequence for VLSI testing has been researched because of effectiveness to more test fault models and low power consumption testing. It is the high fault coverage in deterministic built-in self-test (BIST) with low test cost and short test application time. The sequential single input change (SSIC) sequence used in deterministic BIST is presented in this paper for decreasing the dynamic power, reducing test application time and increasing fault coverage. The selection of seed vectors is the significant technique in deterministic BIST. The critical features of SSIC sequence are proposed for selecting seed vectors. The SSIC sequence generator is designed. The simulation results using benchmark circuits show that the SSIC sequences can increase fault coverage and decrease application time than random SIC sequences. SSIC sequence also has low dynamic power consumption.

With the increasing number of embedded memories in the modern system-on-chips (SOCs), the cost of memory testing becomes significant. Built-in-self-test (BIST) is an effective technique for memory testing. However, BIST has a negative impact on physical design (e.g., area and routing). Moreover, the grouping and placement of memory BIST controllers also greatly influences the test application time. In this paper, we propose an integer linear programming (ILP) approach to optimize the memory BIST design with both physical design (grouping and placement of memory BIST controllers) and test application time considered. Experimental results consistently show that our approach works well in practice.

To produce high-quality and cost-effective multichip systems, they must be designed with test and fault diagnosis as critical design requirements. However, deciding on where and when to test, and whether to apply design for test (DFT) and built-in self test (BIST) at the IC, multichip module (MCM) or board level requires considerable study and evaluation to determine the economics of the various solutions and the payback. In this paper we explore the tradeoffs between various test and rework strategies for multichip module designs. Some of these strategies incorporate various DFT options at both the MCM and IC levels. We will analyze the impact of various cost, yield, and test effectiveness parameters on the final cost and quality of multichip modules. Experimental tradeoff analysis data generated for some leading-edge multichip designs will also be presented. The results clearly indicate that incorporating DFT and BIST with varying degrees at the chip or MCM levels is economically justifiable and results in cost reduction as well as quality improvement. The results also indicates that the MCM cost could vary by about 10–20% depending on the test strategy used. However, proper determination of where and how to test, and whether to employ DFT and BIST at the IC or MCM levels, requires an evaluation of the economics of the various solutions and the payback. That process is highly dependent on the design under consideration and the parameters associated with the available manufacturing environment(s). Hence, one has to be careful about generalizing the lessons learned from specific cases, since it could lead to non optimal solutions. A careful economic modeling of the various design, test and manufacturing parameters is clearly necessary for producing cost-effective high-quality products.

Single input change (SIC) test sequence has been investigated in recent years because it is effective to reduce the test power consumption. Deterministic built-in self-test (BIST) can achieve the high fault coverage with relatively short test application time and low test cost. In this paper, seeds selection scheme of SIC sequences based on deterministic ATPG test patterns is proposed for decreasing the test power consumption and test application time with high test fault coverage. Proper selection of SIC seeds is the key aspect to a successful low power deterministic BIST technique. Furthermore, simulated annealing algorithm is used to optimize the numbers of seeds. A simple hardware structure can implement the generation of SIC sequences. Experimental results based on ISCAS'85 benchmark circuits demonstrate that the proposed algorithm can reduce the number of SIC seeds. Test application time and average power can be decreased, and test fault coverage also keep high compared to random SIC (RSIC) test sequences.

Built-In Self Test (BIST) has been proposed as a powerful technique for addressing the highly complex testing problems of VLSI circuits. In the BIST methodology, two major problems which must be addressed are test generation and response analysis. In this paper, we present an efficient unified procedure, named three-phase cluster partitioning, to automatically synthesize a pseudo-exhaustive test generator for VLSI BIST design. Previous approaches to the problem of test generation have optimized computational efficiency at the expense of the required hardware overhead, or vice versa. Our design procedure is computationally efficient and produces test generation circuitry with low hardware overhead. The procedure minimizes the number of test patterns that are required for pseudo-exhaustive test. Based on three-phase cluster partitioning, a design generator named BISTSYN has been developed and implemented to facilitate the BIST design. The input to the design generator is a circuit description at the gate level which is viewed as a netlist. BISTSYN provides the BIST mechanisms as the output. For those conventional circuits which are extremely unsuitable for pseudo-exhaustive test, BISTSYN employs a circuit partitioning tool, named Autonomous, to partition the combinational portion of the circuit into different structural subcircuits so that each subcircuit can be pseudo-exhaustively tested. We demonstrate the effectiveness of BISTSYN by applying the method to different examples and practical VLSI designs. The detailed comparisons of our benchmark simulation results against those that would be obtained by existing techniques are also presented. >

A new technique called input reduction is proposed for built-in self test (BIST) test pattern generator (TPG) design and test set compaction. This technique analyzes the circuit function and identifies sets of compatible and inversely compatible inputs; inputs in each set can be combined into a test signal in the test mode without sacrificing fault coverage, even if they belong to the same circuit cone. The test signals are used to design BIST TPGs that guarantee the detection of all detectable stuck-at faults in practical test lengths. A deterministic test set generated for the reduced circuit obtained by combining inputs into test signals is usually more compact than that generated for the original circuit. Experimental results show that BIST TPGs based on input reduction achieve complete stuck-at fault coverage in practical test lengths (/spl les/2/sup 30/) for many benchmark circuits. These are achieved with low area overhead and performance penalty to the circuit under test. Results also show that the memory storage and test application time for external testing using deterministic test sets can be reduced by as much as 85%.

The multiple scan chain has been used in DFT (design for test) architectures primarily to reduce test application time. Since power is an emerging problem, in this paper, we present a design technique for multiple scan chains in BIST (built-in self test) to reduce average power dissipation and test application time, while maintaining the fault coverage. First, we partition the scan chain into a set of smaller chains of similar lengths in such a way that the total number of scan transitions in the scan chain is minimized. Then, we use a novel scan re-ordering algorithm in each smaller chain to further reduce the transitions. Experiments on ISCAS'89 benchmarks show up to 46.2% (average 24.4%) power reduction using the proposed technique, compared to the scan partitions given in the RTL description. Unlike previous approaches, our solution is computationally efficient and test-set independent and thus, can be effectively applied to large BIST circuitry.

In recent years, dynamic reconfigurable processor which can achieve reconfiguration with a few cycles is proposed. The fast reconfiguration makes run-time reconfiguration possible, and the run-time reconfiguration gives a new possibility to the dynamic reconfigurable processor, i.e. the dynamic reconfigurable processor can also execute partitioned independent subtasks with repeated reconfigurations and executions. However, to achieve an execution with the run-time reconfiguration, performance should be evaluated with various overheads: reconfiguration, memory accesses, etc. The overheads depend on reconfigurable architectures, and it is generally difficult to evaluate the overhead. As the overhead may critically affect the performance, designers should carefully explore design space for suitable architectures. In this paper, we propose a dynamic reconfigurable architecture exploration method based on Parameterized Reconfigurable Processor model (PRP-model) and task partitioning optimization algorithm for architecture exploration corresponding to proposed PRP-model. Experimental results showed that the proposed PRP-model and the task partitioning algorithm for PRP-model can fast evaluate various reconfigurable architectures, and designers can easily find suitable reconfigurable architectures by changing the PRPmodel parameters.

This paper presents a smoothing technique for the output sequence of linear feedback shift registers (LFSR) to reduce power consumption in test-per-scan built-in self-test (BIST) applications. The proposed smoother is implemented by adding one multiplexer between the LFSR and scan-chain input of a single scan-chain. The size of the multiplexer is determined the desired smoothing degree. When the smoothed sequence of the LFSR is used to feed the test patterns in test-per-scan BIST, it reduces the number of transitions that occur at scan-chain input during scan shift operations by 25% to 50% depending on the smoothing degree, and hence reduces switching activity in the circuit-under-test (CUT) during test application. The proposed technique can be extended to multiple scan-chains BIST, also to test-per-clock applications. Various properties of the proposed technique and the methodology of the design are presented in this paper. Experimental results for the ISCAS'89 benchmark circuits show that the proposed design can reduce the switching activity up to 55% with a negligible effect on the fault coverage and test application time.

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.

Application specific integrated circuits are used to provide real-time performance of handheld devices within the compact physical size and low energy dissipation. However, these circuits are inflexible for any modification like redesign and refabrication. Reconfigurable architectures are promising alternative for conventional computing devices such as application-specific integrated circuits. It provides high-level flexibility to adapt the applications through dynamic hardware customization even after fabrication. A reconfigurable computing system design considers the peculiarities of the targeted application domain along with architectural issues like dynamic reconfiguration, partial reconfiguration, hardware/software co-design and context management. A brief survey has been carried out to understand the concepts and applications of CGRA, FPGA, SoC, NoC, MPSoC, dynamic partial reconfiguration, hardware/software co-design, design-space exploration, multi-objective optimization, genetic algorithm and reconfigurable computing on wireless communications. This paper deals with the survey on modeling, design, implementation and evaluation of coarse-grained dynamically reconfigurable processor architectures targeting the real-time embedded computing domain.

A hybrid DFT method is proposed to reduce the hardware penalty of traditional DFT methods and test generation time. It takes advantages of both traditional DFT methods like scan and DFT methods which control clocks for testability. The hardware scheme and test generation algorithm are presented. Test generation results for ISCAS '89 circuits have been generated and showed an improvement in test generation time and fault coverage.