A Self-Reconfiguring IEEE 1687 Network for Fault Monitoring

Efficient handling of faults during operation is highly dependent on the interval (latency) from the time embedded instruments detect errors to the time when the fault manager localizes the errors. In this paper, we propose a self-reconfiguring IEEE 1687 network in which all instruments that have detected errors are automatically included in the scan path. To enable self-reconfiguration, we propose a modified segment insertion bit (SIB) compliant to IEEE 1687. We provide time analyses on error detection and fault localization for single and multiple faults, and we suggest how the self-reconfiguring IEEE 1687 network should be designed such that time for error detection and fault localization is kept low and deterministic. For validation, we implemented and performed post-layout simulations for one self-reconfiguring network. We show that compared to previous schemes, our proposed network significantly reduces the fault localization time

Graceful Degradation of Reconfigurable Scan Networks

Modern integrated circuits (ICs) include thousands of on-chip instruments to ensure that specifications are met and maintained. Scalable and flexible access to these instruments is offered by reconfigurable scan networks (RSNs), e.g. IEEE Std. 1687. As RSNs themselves can become faulty, there is a need to exclude and bypass faulty parts so that remaining instruments can be used. To avoid keeping track and updating description languages for each individual IC, we propose an on-chip hardware block that makes adjustments according to fault status of a particular IC. We show how this block enables test for faulty scan- chains, localization of faulty scan-chains, and repair by excluding faulty scan-chains. We made implementations and experiments to evaluate the overhead in terms of transported data and area

New techniques for functional testing of microprocessor based systems

Electronic devices may be affected by failures, for example due to physical defects. These defects may be introduced during the manufacturing process, as well as during the normal operating life of the device due to aging. How to detect all these defects is not a trivial task, especially in complex systems such as processor cores. Nevertheless, safety-critical applications do not tolerate failures, this is the reason why testing such devices is needed so to guarantee a correct behavior at any time. Moreover, testing is a key parameter for assessing the quality of a manufactured product. Consolidated testing techniques are based on special Design for Testability (DfT) features added in the original design to facilitate test effectiveness. Design, integration, and usage of the available DfT for testing purposes are fully supported by commercial EDA tools, hence approaches based on DfT are the standard solutions adopted by silicon vendors for testing their devices. Tests exploiting the available DfT such as scan-chains manipulate the internal state of the system, differently to the normal functional mode, passing through unreachable configurations. Alternative solutions that do not violate such functional mode are defined as functional tests. In microprocessor based systems, functional testing techniques include software-based self-test (SBST), i.e., a piece of software (referred to as test program) which is uploaded in the system available memory and executed, with the purpose of exciting a specific part of the system and observing the effects of possible defects affecting it. SBST has been widely-studies by the research community for years, but its adoption by the industry is quite recent. My research activities have been mainly focused on the industrial perspective of SBST. The problem of providing an effective development flow and guidelines for integrating SBST in the available operating systems have been tackled and results have been provided on microprocessor based systems for the automotive domain. Remarkably, new algorithms have been also introduced with respect to state-of-the-art approaches, which can be systematically implemented to enrich SBST suites of test programs for modern microprocessor based systems. The proposed development flow and algorithms are being currently employed in real electronic control units for automotive products. Moreover, a special hardware infrastructure purposely embedded in modern devices for interconnecting the numerous on-board instruments has been interest of my research as well. This solution is known as reconfigurable scan networks (RSNs) and its practical adoption is growing fast as new standards have been created. Test and diagnosis methodologies have been proposed targeting specific RSN features, aimed at checking whether the reconfigurability of such networks has not been corrupted by defects and, in this case, at identifying the defective elements of the network. The contribution of my work in this field has also been included in the first suite of public-domain benchmark networks