Test Wrapper and Test Access Mechanism Co-Optimization for System-on-Chip

Test access mechanisms (TAMs) and test wrappers are integral parts of a system-on-chip (SOC) test architecture. Prior research has concentrated on only one aspect of the TAM/wrapper design problem at a time, i.e., either optimizing the TAMs for a set of pre-designed wrappers, or optimizing the wrapper for a given TAM width. In this paper, we address a more general problem, that of carrying out TAM design and wrapper optimization in conjunction. We present an efficient algorithm to construct wrappers that reduce the testing time for cores. Our wrapper design algorithm improves on earlier approaches by also reducing the TAM width required to achieve these lower testing times. We present new mathematical models for TAM optimization that use the core testing time values calculated by our wrapper design algorithm. We further present a new enumerative method for TAM optimization that reduces execution time significantly when the number of TAMs being designed is small. Experimental results are presented for an academic SOC as well as an industrial SOC.     

基于云进化算法的NoC测试规划

针对NoC测试时,如何在功耗限制下利用有限的片上资源最大化并行测试,以优化NoC测试时间的问题,文中提出一种利用云进化算法进行测试规划的方法,可以有效提高测试效率。该方法复用NoC的片上资源作为TAM,采用非抢占式测试和XY路由方式,通过云进化算法优化待测IP核在各条TAM上的分配方式寻找最佳方案。在ITC'02标准电路上的实验结果表明,该方法有效降低了测试时间,提高了测试效率。     

An Integrated Approach to Testing Embedded Cores and Interconnects Using Test Access Mechanism (TAM) Switch

The present paper introduces a new strategy for testing embedded cores using Test Access Mechanism (TAM) switches. An algorithm has been proposed for testing the cores using the TAM switch architecture. In addition, a scheme for testing the interconnections between cores in parallel is also presented. Experiments have been carried out on several synthetic SOC benchmarks. Results show significant optimization of area overhead as well as test time.     

Test-access mechanism optimization for core-based three-dimensional SOCs

Embedded cores in a core-based system-on-chip (SOC) are not easily accessible via chip I/O pins. Test-access mechanisms (TAMs) and test wrappers (e.g., the IEEE Standard 1500 wrapper) have been proposed for the testing of embedded cores in a core-based SOC in a modular fashion. We show that such a modular testing approach can also be used for emerging three-dimensional integrated circuits based on through-silicon vias (TSVs). Core-based SOCs based on 3D IC technology are being advocated as a means to continue technology scaling and overcome interconnect-related bottlenecks. We present an optimization technique for minimizing the post-bond test time for 3D core-based SOCs under constraints on the number of TSVs, the TAM bitwidth, and thermal limits. The proposed optimization method is based on a combination of integer linear programming, LP-relaxation, and randomized rounding. It considers the Test Bus and TestRail architectures, and incorporates wire-length constraints in test-access optimization. Simulation results are presented for the ITC 02 SOC Test Benchmarks and the test times are compared to that obtained when methods developed earlier for two-dimensional ICs are applied to 3D ICs. The test time dependence on various 3D parameters (e.g. 3D placement, the number of layers, thermal constraints, and the number of TSVs) is also studied.     

Test infrastructure design for mixed-signal SOCs with wrapped analog cores

Many system-on-chips (SOCs) today contain both digital- and analog-embedded cores. Even though the test cost for such mixed-signal SOCs is significantly higher than that for digital SOCs, most prior research in this area has focused exclusively on digital cores. We propose a low-cost test development methodology for mixed-signal SOCs that allows the analog and digital cores to be tested in a unified manner, thereby minimizing the overall test cost. The analog cores in the SOC are wrapped such that they can be accessed using a digital test access mechanism (TAM). We evaluate the impact of the use of analog test wrappers on area overhead and test time. To reduce area overhead, we present an analog test wrapper optimization technique, which is then combined with TAM optimization in a cost-oriented heuristic approach for test scheduling. We also demonstrate the feasibility of using analog wrappers by presenting transistor-level simulations for an analog wrapper and a representative core. We present experimental results for three SOCs from the ITC '02 test benchmarks that have been augmented with three analog cores: an I-Q transmit path pair and an audio CODEC path used in cellular phone applications.     

A Graph-Based Approach to Power-Constrained SOC Test Scheduling

The test scheduling problem is one of the major issues in the test integration of system-on-chip (SOC), and a test schedule is usually influenced by the test access mechanism (TAM). In this paper we propose a graph-based approach to power-constrained test scheduling, with TAM assignment and test conflicts also considered. By mapping a test schedule to a subgraph of the test compatibility graph, an interval graph recognition method can be used to determine the order of the core tests. We then present a heuristic algorithm that can effectively assign TAM wires to the cores, given the test order. With the help of the tabu search method and the test compatibility graph, the proposed algorithm allows rapid exploration of the solution space. Experimental results for the ITC02 benchmarks show that short test length is achieved within reasonable computation time.     

Searching for Global Test Costs Optimization in Core-Based Systems

This paper proposes a comprehensive model for test planning and design space exploration in a core-based environment. The proposed approach relies on the reuse of available system resources for the definition of the test access mechanism, and for the optimization of several cost factors (area overhead, pin count, power constraints and test time). The use of an expanded test access model and its concurrent definition with the system test schedule makes it possible the search for a cost effective global solution. Experimental results over the ITC'02 SOC Test Benchmarks show the variety of trade-offs that can be explored using the proposed model, and its effectiveness on optimizing the system test planning.     

Analysis of Test Application Time for Test Data Compression Methods Based on Compression Codes

We present an analysis of test application time for test data compression techniques that are used for reducing test data volume and testing time in system-on-a-chip (SOC) designs. These techniques are based on data compression codes and on-chip decompression. The compression/decompression scheme decreases test data volume and the amount of data that has to be transported from the tester to the SOC. We show via analysis as well as through experiments that the proposed scheme reduces testing time and allows the use of a slower tester. Results on test application time for the ISCAS'89 circuits are obtained using an ATE testbench developed in VHDL to emulate ATE functionality.     

IPRM: IP core resource multiplexing of core wrapper design for reducing test application time in DVFS-based multicore SoCs

A modify wrapper/test access mechanism(TAM) structure is described to explore the maximal potential capacity of TAM, named “IP cores resource multiplexing(IPRM)”, reducing test application time for DVFS-based multicore System-on-Chips(MSoCs). The IPRM core wrappers, different from standard wrappers, enable to isolated core wrapper resource again to store test data for embedded cores under test. An integer linear programming (ILP) formulation with IPRM wrapper is proposed to improve multi-site test. Experimental results of the ITC’02 SoC Benchmark show that IPRM core wrapper reduces the burdens on ATE effectively, and can reduce the test application time by 10–50%.     

Test Scheduling for Network-on-Chip Using XY-Direction Connected Subgraph Partition and Multiple Test Clocks

It is attractive to reuse the on-chip functional interconnects as test access mechanism (TAM) in network-on-chip (NoC) system testing. However, in the methodology of NoC-reuse as TAM, the influence factors in NoC testing significantly increased. To further reduce test time and show significant gains over other work, we propose XY-direction connected subgraph partition (XYCSP) approach to eliminate the path conflicts before testing, and concurrently determine the position of test access points. We then present a multiple test clock strategy to bridge the gap between the NoC channel bandwidth and the core test wrapper bandwidth. With the help of adaptive probability gate quantum-inspired evolutionary algorithm (APGQEA) strategy, which blends adaptive strategy and multi-nary oriented techniques, the proposed NoC test scheduling algorithm permits quick exploration and exploitation of the solution space. Moreover, power constraints are also taken into account. Experimental results for the ITC’02 benchmarks show that the proposed scheme can achieve shorter test time compared to prior works.     

Design of reconfigurable access wrappers for embedded core based SoC test

Testing of embedded core based system-on-chip (SoC) ICs is a well known problem, and the upcoming IEEE P1500 Standard on Embedded Core Test (SECT) standard proposes DFT solutions to alleviate it. One of the proposals is to provide every core in the SoC with test access wrappers. Previous approaches to the problem of wrapper design have proposed static core wrappers, which are designed for a fixed test access mechanism (TAM) width. We present the first report of a design of reconfigurable core wrappers which allow for a dynamic change in the width of the TAM executing the core test. Analysis of the corresponding scheduling problem indicates that good approximate schedules can be achieved without significant computational effort. Specifically, we derive a O(N/sub C//sup 2/B) time algorithm which can compute near optimal SoC test schedules, where N/sub C/ is the number of cores and B is the number of top level TAMs. Experimental results on benchmark SoCs are presented which improve upon integer programming based methods, not only in the quality of the schedule, but also significantly reduce the computation time.     

Wafer-Level Modular Testing of Core-Based SoCs

Product cost is a major driver in the consumer electronics market, which is characterized by low profit margins and the use of core-based system-on-chip (SoC) designs. Packaging has been recognized as a significant contributor to the product cost for such SoCs. To reduce packaging cost and the test cost for packaged chips, wafer-level testing (wafer sort) is used in the semiconductor industry to screen defective dies. However, since test time is a major practical constraint for wafer sort, even more so than for package test, not all the scan-based digital tests can be applied to the die under test. We present an optimal test-length selection technique for wafer-level testing of core-based SoCs. This technique, which is based on a combination of statistical yield modeling and integer linear programming, allows us to determine the number of patterns to use for each embedded core during wafer sort such that the probability of screening defective dies is maximized for a given upper limit on the SoC test time. We also present a heuristic method to handle large next-generation SoC designs. Simulation results are presented for five of the ITC'02 SoC Test benchmarks, and the optimal test-length selection approach is compared with the heuristic method.     

Constructing IP cores’ transparency paths for SoC test access using greedy search

Today’s SoC design demands efficient test access mechanism to develop and perform manufacturing test. Transparency based methods have their advantages for IP cores’ test reuse in SoC level. In this paper, an IP core transparency paths construction approach employing greedy search strategy based on gate-level heuristic information is proposed. With these transparency paths, IP cores can consecutively transfer one test per clock cycle from their inputs to outputs, and thus can be used in transparency-based test scheme to benefit at-speed testing and decrease the demand of parallel TAMs. The experimental results show lower extra overhead needed in our approach than conventional boundary scan and previous RT level approaches.     

Deterministic Test Vector Compression/Decompression for Systems-on-a-Chip Using an Embedded Processor

A novel approach for using an embedded processor to aid in deterministic testing of the other components of a system-on-a-chip (SOC) is presented. The tester loads a program along with compressed test data into the processor's on-chip memory. The processor executes the program which decompresses the test data and applies it to scan chains in the other components of the SOC to test them. The program itself is very simple and compact, and the decompression is done very rapidly, hence this approach reduces both the amount of data that must be stored on the tester and reduces the test time. Moreover, it enables at-speed scan shifting even with a slow tester (i.e., a tester whose maximum clock rate is slower than the SOC's normal operating clock rate). A procedure is described for converting a set of test cubes (i.e., test vectors where the unspecified inputs are left as X's) into a compressed form. A program that can be run on an embedded processor is then given for decompressing the test cubes and applying them to scan chains on the chip. Experimental results indicate a significant amount of compression can be achieved resulting in less data that must be stored on the tester (i.e., smaller tester memory requirement) and less time to transfer the test data from the tester to the chip.     

ATE射频测试板低成本解决方案

近年来国内无线通讯市场发展迅猛,射频芯片的出货量也快速增长,射频芯片不同于其他SoC芯片,往往是市场周期短,更新速度快,这给芯片的量产测试带来挑战,ATE射频测试板作为测试的重要组件,成为制约测试开发和成本的最关键因素,ADVANTEST推出的低成本射频测试板兼顾了开发效率和测试成本的平衡性,给射频芯片的量产测试带来了...     

SOC芯片的高速模拟IP测试方法学

很多SoC芯片里会使用SATA物理层,PCIE物理层以及DDR2/DDR3物理层等高速模拟IP。这些高速模拟IP需要被自动测试设备完整的测试。自动测试设备的高速测试选项就是用来测试高速IP,但随之而来的是测试成本的增加。智原科技利用内建自测试方法来取代费钱的自动测试设备的高速测试选项。内建自测试提供了最具成本效率的方法。高速模拟IP内建自测试的故障覆盖率很高,所以我们不再需要自动测试设备的高速测试选项及其所带来的高成本。     

复用NoC测试IP芯核测试存取链优化配置

论述了层次型IP芯核不同测试模式之间的约束关系,给出了层次型IP芯核的测试壳结构,提出了一种复用片上网络测试内嵌IP芯核的启发式测试存取链优化配置方法.该方法可有效减小测试数据分组数量和被测芯核的测试时间.使用片上网络测试平台,在测试基准电路集ITC'02中的基准电路p22810上进行了实验验证.     

Fast algorithms for test optimization of core based 3D SoC

The use of 3D-IC technology has become quite widespread in designing core-based systems-on-chip (SoCs). Concomitantly, testing of cores and inter-layer through-silicon-vias (TSVs) spanning through different layers of 3D chips has become an important problem in the manufacturing cycle. Testing 3D-SoCs is more challenging compared to their 2D counterparts because of the complexity of their design and power management issues. Also, the test procedure demands substantially more power than what is required in the normal functional mode, and hence, stringent thermal constraints during test need to be fulfilled to safeguard future performance and reliability of the chip. Since the overall 3D infrastructure depends on routing layer assignments, core allocation, and the geometry of TSV locations, these parameters should be given due consideration while designing the test-access-mechanism (TAM) that aims for minimizing overall test time satisfying power and TSV constraints. In this paper, we present a three-stage algorithm for reducing the test time in automated post-bond core-based 3D-SoCs, under a set of given constraints on test power, TAM-width, and the number of available TSVs. The proposed algorithm, when run on several ITC-02 SoC benchmarks, outperforms the algorithms presented in earlier work with respect to CPU-time, and additionally, reduces test time in many instances.     

System-on-chip test scheduling with reconfigurable core wrappers

The problem with increasing test application time for testing core-based system-on-chip (SOC) designs is addressed with test architecture design and test scheduling. The scan-chains at each core are configured into a set of wrapper-chains, which by a core wrapper are connected to the test access mechanism (TAM), and the tests are scheduled in such a way that the test time is minimized. In this paper, we make use of reconfigurable core wrappers that, in contrast to standard wrappers, can dynamically change (reconfigure) the number of wrapper-chains during test application. We show that by using reconfigurable wrappers the test scheduling problem is equivalent to independent job scheduling on identical machines, and we make use of an existing preemptive scheduling algorithm that produces an optimal solution in linear time (O(n); n is the number of tests). We also show that the problem can be solved without preemption, and we extend the algorithm to handle: 1) test conflicts due to interconnection tests and 2) cases when the test time of a core limits an optimal usage of the TAM. The overhead in logic is given by the number of configurations, and we show that the upper-bound is three configurations per core. We compare the proposed approach with the existing technique and show, in comparison, that our technique is 2% less from lower bound.     

基于跨度和虚拟层的三维芯核测试外壳扫描链优化方法

为减少三维芯核绑定前和绑定后的测试时间,降低测试成本,提出了基于跨度和虚拟层的三维芯核测试外壳扫描链优化方法.所提方法首先通过最大化每条测试外壳扫描链的跨度,使得绑定前高层电路和低层电路的测试外壳扫描链数量尽可能相等.然后,在TSVs(Through Silicon Vias)数量的约束下,逐层的将虚拟层中的扫描元素分配到测试外壳扫描链中,以平衡绑定前后各条测试外壳扫描链的长度.实验结果表明,所提方法有效地减少了三维芯核绑定前后测试的总时间和硬件开销.