We describe an integrated framework for system-on-chip (SOC) test automation. Our framework is based on a new test access mechanism (TAM) architecture consisting of flexible-width test buses that can fork and merge between cores. Test wrapper and TAM cooptimization for this architecture is performed by representing core tests using rectangles and by employing a novel rectangle packing algorithm for test scheduling. Test scheduling is tightly integrated with TAM optimization and it incorporates precedence and power constraints in the test schedule, while allowing the SOC integrator to designate a group of tests as preemptable. Test preemption helps avoid hardware and power consumption conflicts, thereby leading to a more efficient test schedule. Finally, we study the relationship between TAM width and tester data volume to identify an effective TAM width for the SOC.

Recent advances in tester technology have led to automatic test equipment (ATE) that can operate at up to GHz speeds. However, system-on-chip (SOC) scan chains are typically run at lower frequencies, e.g., 10-50 MHz. The use of high-speed ATE channels to drive slower scan chains leads to an underutilization of resources, thereby resulting in an increase in SOC testing time. We present a new test planning technique to reduce the testing time and test cost by matching high-speed ATE channels to slower scan chains using the concept of virtual test access architectures. We also present a new TAM optimization framework based on Lagrange multipliers and analyze the impact of virtual TAMs on the overall SOC test power consumption for one of the ITC'02 benchmarks. Experimental results for TAM optimization based on Lagrange multipliers and virtual TAMs are presented for three industrial circuits from the set of ITC'02 SOC test benchmarks.

Motivated by the presence of mega-cores in hierarchical systems-on-a-chip, this paper describes a new framework for the design space exploration of multi-level test access mechanisms. The proposed solution can rapidly analyze the tradeoffs between test application time and area overhead and it facilitates test data reuse for hard mega-cores. 1

Abstract—Concurrent testing of the cores in a core-based systemon-chip reduces the test application time but increases the test power consumption. Power models, test architecture design, and scheduling algorithms have been proposed to schedule the tests as concurrently as possible while respecting the power budget. The commonly used global peak power model, with a single value capturing the power dissipated by a core when tested, is simple for a scheduling algorithm to handle but is pessimistic. In this paper, we propose a cycle-accurate power model with a power value per clock cycle and a corresponding test architecture design and scheduling algorithm. The power model takes into account the switching activity in the scan chains caused by both the test stimuli and the expected test responses during scan-in, launch-and-capture, and scan-out. Furthermore, we allow a unique power model per wrapper-chain configuration as the activity in a core will be different depending on the number of wrapper chains at a core. Through circuit simulations on ISCAS’89 benchmarks, we demonstrate a high correlation between the real test power dissipation and our cycle-accurate test power model. Extensive experiments on ITC’02 benchmarks and an industrial design show that the testing time can be reduced substantially by using the proposed cycle-accurate test power model. Index Terms—Power constraint, power estimation, scan chain, system-on-chip (SoC), test architecture design, test power, test scheduling. I.

Test planning for core-based system-on-a-chip (SOC) designs is necessary to reduce testing time and test cost. In this paper, we survey recent advances in test planning that address the problems of test access and constrained test scheduling for core-based SOCs. We describe several test access architectures proposed by research groups in industry and academia, as well as a wide range of methodologies for the optimization of such architectures. An extensive list of references to prior and current work in the SOC test planning domain is included.

This work discusses the impact of power consumption on the test time of core-based systems, when an available on-chip network is reused as test access mechanism. A previously proposed technique for the reuse of an on-chip network is extended to consider power consumption during test, while minimizing the system testing time. Experimental results with the ITC'02 SoC benchmarks show that although power constraints can preclude the full exploration of the network parallelism, this platform is still a powerful mechanism for the system test time reduction at a very low cost.

Test access mechanisms (TAMs) are an important component of a system-on-chip (SOC) test architecture. TAM optimization is necessary to minimize the SOC testing time. We present a fast, heuristic technique for TAM optimization and demonstrate its scalability for several industrial SOCs. Since the TAM optimization problem is-hard, recently proposed methods based on integer linear programming and exhaustive enumeration can be used to design limited test architectures with only a very small number of TAMs in a reasonable amount of time. In this paper, we explore a larger solution-space to design efficient test architectures with more TAMs. We show that the SOC testing times obtained using the new heuristic algorithm are comparable to or lower than the testing times obtained using enumeration. Moreover, significant reduction can be obtained in the CPU time compared to enumeration.

Abstract—Multilevel test access mechanism (TAM) optimization is necessary for modular testing of hierarchical systems-on-chip (SOCs) that contain older-generation SOCs as embedded megacores. We consider the case where these older-generation SOCs are used as hard cores in new SOC designs, and they are delivered to the system integrator as optimized and technology-mapped layouts. We present three hierarchical test planning and TAM optimization flows that exploit recent advances in TAM design for flattened SOC hierarchies. These techniques are based on the reuse of existing TAM architectures within megacores and the optimization of the top-level TAM under the constraints imposed by “TAM-ed ” megacores that are delivered either with or without a wrapper. We present a new megacore wrapper-design technique for the latter case. Unlike prior methods that assume flat test hierarchies, the proposed methods are directly applicable to real-world design-transfer models involving hard megacores between the core vendor and the system integrator for hierarchical SOCs. Experimental results are presented for four ITC’02 SOC test benchmarks that contain megacores. Index Terms—Design transfer and hand-off model, hard cores, megacores, test access mechanism (TAM), TAM optimization, testing time, test wrappers. I.

Recent advances in tester technology have led to automatic test equipment (ATE) that can operate at up to several hundred MHz. However, system-on-chip (SOC) scan chains typically run at lower frequencies (10-50 MHz). The use of high-speed ATE channels to drive slower scan chains leads to an underutilization of resources, thereby resulting in an increase in testing time. We present a new technique to reduce the testing time and test cost by matching highspeed ATE channels to slower scan chains using the concept of virtual test access mechanisms (TAMs). We also present a new TAM optimization framework based on Lagrange multipliers. Experimental results are presented for three industrial circuits from the ITC'02 SOC test benchmarks.

Abstract — This paper presents a new approach to active sub-threshold leakage reduction using task migration. The main idea is to replicate a hot module in a design so as to actively migrate its computation at regular intervals, reducing the on-chip temperature and thereby the subthreshold leakage. We observe that choosing which blocks to migrate and their placement in a floorplan is a chicken-and-egg problem. To solve this, we propose a two step floorplanning methodology, wherein, given a base floorplan, we first choose the modules to replicate and then effectively utilize the deadspaces in it by exploiting the lateral conduction of heat in the floorplan to place a module’s replica. With an optimized floorplan, using task migration we obtain an average savings of 29 % in the active sub-threshold leakage at the expense of about 6 % additional area. I.