Gert Jervan

Test cost minimization for hybrid BIST

This paper describes a hybrid BIST solution for testing systems-on-chip which combines pseudorandom test patterns with stored deterministic test patterns. A method is proposed to find the optimal balance between pseudorandom and stored test patterns to perform core test with minimum time and memory, without losing test quality. Two accurate algorithms are proposed for finding the optimal time-moment to stop pseudorandom test generation and to apply stored patterns. To speed up the optimization procedure, a method is proposed for fast estimation of the expected cost for different possible solutions with very low computational cost. Experimental results have demonstrated the feasibility of the proposed approach for cost optimization of hybrid BIST.

High-level and hierarchical test sequence generation

Test generation at the gate-level produces high-quality tests but is computationally expensive in the case of large systems. Recently, several research efforts have investigated the possibility of devising test generation methods and tools to work on high-level descriptions. The goal of these methods is to provide the designers with testability information and test sequences in the early design stages. The cost for generating test sequences in the high abstraction levels is often lower than that for generating test sequences at the gate-level, with comparable or even higher fault coverage. This paper first analyses several high-level fault models in order to select the most suitable one for estimating the testability of circuits by reasoning on their behavioral descriptions and for guiding the test generation process at the behavioral level. We assess then the effectiveness of high-level test generation with a simple ATPG algorithm, and present a novel high-level hierarchical test generation approach to improve the results obtained by a pure high-level test generator.

A hybrid BIST architecture and its optimization for SoC testing

This paper presents a hybrid BIST architecture and methods for optimizing it to test system-on-chip in a cost effective way. The proposed self-test architecture can be implemented either only in software or by using some test related hardware. In our approach we combine pseudorandom test patterns with stored deterministic test patterns to perform core test with minimum time and memory, without losing test quality. We propose two algorithms to calculate the cost of the rest process. To speed up the optimization procedure, a Tabu search based method is employed for finding the global cost minimum. Experimental results have demonstrated the feasibility and efficiency of the approach and the significant decreases in overall test cost.

Turbo Tester: A CAD System for Teaching Digital Test

Traditional VLSI CAD/CAT systems for workstations are both costly and unable to handle large numbers of students simultaneously in educational courses. During recent years, many different low-cost tools running on PCs have been developed to fill this gap. They include the major basic tools for IC design: schematic capture, layout editors, simulators and place-and-route tools. However, low-cost systems for solving a wide class of tasks from the test domain, especially for teaching purposes, are missing.

Hybrid BIST time minimization for core-based systems with STUMPS architecture

This paper presents a solution to the test tone minimization problem for core-based systems that contain sequential cores with STUMPS architecture. We assume a hybrid BIST approach, where a test set is assembled, for each core, from pseudo-random test patterns that are generated online, and deterministic test patterns that are generated offline and stored in the system. We propose a methodology to find the optimal combination of pseudorandom and deterministic test sets of the whole system, consisting of multiple cores, under given memory constraints, so that the total test time is minimized. Our approach employs a fast estimation methodology in order to avoid exhaustive search and to speed-up the calculation process. Experimental results have shown the efficiency of the algorithm to find near optimal solutions.

Fast test cost calculation for hybrid BIST in digital systems

The paper presents a hybrid BIST solution for testing systems-on-chip which combines pseudorandom test patterns with stored precomputed deterministic test patterns. A procedure is proposed for fast calculation of the cost of hybrid BIST at different lengths of pseudorandom test to find an optimal balance between test sets, and to perform a core test with minimum cost of both time and memory, and without losing test quality. Compared to the previous approach, based on iterative use of deterministic ATPG for evaluating the cost of stored patterns, a new, extremely fast procedure is proposed, which calculates costs on a basis of fault table manipulations. Experiments on the ISCAS benchmark circuits show that the new procedure is about two orders of magnitude faster than the previous one.

Energy minimization for hybrid BIST in a system-on-chip test environment

This paper addresses the energy minimization problem for system-on-chip testing. We assume a hybrid BIST test architecture where a combination of deterministic and pseudorandom test sequences is used. The objective of our proposed technique is to find the best ratio of these sequences so that the total energy is minimized and the memory requirements for the deterministic test set are met without sacrificing test quality. We propose two different heuristic algorithms and a fast estimation method that enables considerable reduction of the computation time. Experimental results have shown the efficiency of the approach for finding reduced energy solutions with low computational overhead.

An improved estimation methodology for hybrid BIST cost calculation

This paper presents an improved estimation methodology for hybrid BIST cost calculation. In a hybrid BIST approach the test set is assembled from pseudorandom and deterministic test patterns. The efficiency of the hybrid BIST approach is largely determined by the ratio of those test patterns in the final test set. Unfortunately exact algorithms for finding the test sets are computationally very expensive. Therefore in this paper we propose an improved estimation methodology for fast calculation of the hybrid test set. The methodology is based on real fault simulation results and experimental results have shown that the method is more accurate than the statistical method proposed earlier.

Test time minimization for hybrid BIST of core-based systems

This paper presents a solution to the test time minimization problem for core-based systems. We assume a hybrid BIST approach, where a test set is assembled, for each core, from pseudorandom test patterns that are generated online, and deterministic test patterns that are generated off-line and stored in the system. In this paper we propose an iterative algorithm to find the optimal combination of pseudorandom and deterministic test sets of the whole system, consisting of multiple cores, under given memory constraints, so that the total test time is minimized. Our approach employs a fast estimation methodology in order to avoid exhaustive search and to speed-up the calculation process. Experimental results have shown the efficiency of the algorithm to find near optimal solutions.

A Framework for Combining Concurrent Checking and On-Line Embedded Test for Low-Latency Fault Detection in NoC Routers

The focus of the paper is detection of faults in NoC routers by combining concurrent checkers with embedded on-line test to enable cost-effective trade-offs between area-overhead and test coverage. First, we propose a framework of tools for formally evaluating the quality of the checkers and for optimizing the overhead area with given fault coverage constraints. The stress is in particular on the minimization of the error detection latency, which is a crucial aspect in order to eliminate (or limit) error propagation. Second, the concurrent checkers will be complemented by embedded on-line test packets which are to be applied as a periodic routine during the idle periods in router operation. The framework together with the corresponding methodology has been successfully applied to a realistic case-study of a fault tolerant NoC router design. The case study shows that combining concurrent routers with embedded test allows reducing the area overhead of the checkers from 31--35% down to 1.5--10% without sacrificing the fault coverage.