1,822 research outputs found
Towards Comparing the Robustness of Synchronous and Asynchronous Circuits by Fault Injection
As transient error rates are growing due to smaller feature sizes,
designing reliable synchronous circuits becomes increasingly
challenging. Asynchronous logic design constitutes a promising
alternative with respect to robustness and stability. In particular,
delay-insensitive asynchronous circuits provide interesting properties,
like an inherent resilience to delay-faults
Deductive Fault Simulation Technique for Asynchronous Circuits
Fault simulator for acpASC needs to deal with hazards, oscillations and races. The simplest algorithm for simulating faults is the serial fault simulation technique which was successfully used for the acpASC. Faster fault simulation techniques, for example deductive fault simulation, was previously used for the combinational and synchronous sequential circuits only. In this paper a deductive fault simulator for the stuck-at faults of acSI acpASC is presented. An algorithm for the propagation of the fault lists is proposed which can deal with the complex gates of the acpASC. The implemented deductive fault simulator was tested using acSI benchmark circuits. The experimental results show significant reduction of the computation time and negligible increase of the memory requirements in comparison with the serial fault simulation technique
A review of convex approaches for control, observation and safety of linear parameter varying and Takagi-Sugeno systems
This paper provides a review about the concept of convex systems based on Takagi-Sugeno, linear parameter varying (LPV) and quasi-LPV modeling. These paradigms are capable of hiding the nonlinearities by means of an equivalent description which uses a set of linear models interpolated by appropriately defined weighing functions. Convex systems have become very popular since they allow applying extended linear techniques based on linear matrix inequalities (LMIs) to complex nonlinear systems. This survey aims at providing the reader with a significant overview of the existing LMI-based techniques for convex systems in the fields of control, observation and safety. Firstly, a detailed review of stability, feedback, tracking and model predictive control (MPC) convex controllers is considered. Secondly, the problem of state estimation is addressed through the design of proportional, proportional-integral, unknown input and descriptor observers. Finally, safety of convex systems is discussed by describing popular techniques for fault diagnosis and fault tolerant control (FTC).Peer ReviewedPostprint (published version
Integrated analysis of error detection and recovery
An integrated modeling and analysis of error detection and recovery is presented. When fault latency and/or error latency exist, the system may suffer from multiple faults or error propagations which seriously deteriorate the fault-tolerant capability. Several detection models that enable analysis of the effect of detection mechanisms on the subsequent error handling operations and the overall system reliability were developed. Following detection of the faulty unit and reconfiguration of the system, the contaminated processes or tasks have to be recovered. The strategies of error recovery employed depend on the detection mechanisms and the available redundancy. Several recovery methods including the rollback recovery are considered. The recovery overhead is evaluated as an index of the capabilities of the detection and reconfiguration mechanisms
Component-based simulation for a reconfiguration study of transitic systems
This paper is organized as follows. Part A presents the context of reconfiguring transitic systems and the main idea in implementing the decision step. It comprises sections 1 to 3. Section 3 presents an example that illustrates the concepts presented in the next sections. Parts B and C express the models and principles used to simulate transitic systems, the result of which will be helpful for choosing the new configuration. Part B focuses mainly on models. It comprises sections 4 to 6. Part C focuses mainly on simulation principles. It comprises sections 7 to 10
A fault-tolerant multiprocessor architecture for aircraft, volume 1
A fault-tolerant multiprocessor architecture is reported. This architecture, together with a comprehensive information system architecture, has important potential for future aircraft applications. A preliminary definition and assessment of a suitable multiprocessor architecture for such applications is developed
Test and Testability of Asynchronous Circuits
The ever-increasing transistor shrinkage and higher clock frequencies are causing serious clock distribution, power management, and reliability issues. Asynchronous design is predicted to have a significant role in tackling these challenges because of its distributed control mechanism and on-demand, rather than continuous, switching activity.
Null Convention Logic (NCL) is a robust and low-power asynchronous paradigm that introduces new challenges to test and testability algorithms because 1) the lack of deterministic timing in NCL complicates the management of test timing, 2) all NCL gates are state-holding and even simple combinational circuits show sequential behaviour, and 3) stuck-at faults on gate internal feedback (GIF) of NCL gates do not always cause an incorrect output and therefore are undetectable by automatic test pattern generation (ATPG) algorithms.
Existing test methods for NCL use clocked hardware to control the timing of test. Such test hardware could introduce metastability issues into otherwise highly robust NCL devices. Also, existing test techniques for NCL handle the high-statefulness of NCL circuits by excessive incorporation of test hardware which imposes additional area, propagation delay and power consumption.
This work, first, proposes a clockless self-timed ATPG that detects all faults on the gate inputs and a share of the GIF faults with no added design for test (DFT). Then, the efficacy of quiescent current (IDDQ) test for detecting GIF faults undetectable by a DFT-less ATPG is investigated. Finally, asynchronous test hardware, including test points, a scan cell, and an interleaved scan architecture, is proposed for NCL-based circuits. To the extent of our knowledge, this is the first work that develops clockless, self-timed test techniques for NCL while minimising the need for DFT, and also the first work conducted on IDDQ test of NCL.
The proposed methods are applied to multiple NCL circuits with up to 2,633 NCL gates (10,000 CMOS Boolean gates), in 180 and 45 nm technologies and show average fault coverage of 88.98% for ATPG alone, 98.52% including IDDQ test, and 99.28% when incorporating test hardware. Given that this fault coverage includes detection of GIF faults, our work has 13% higher fault coverage than previous work. Also, because our proposed clockless test hardware eliminates the need for double-latching, it reduces the average area and delay overhead of previous studies by 32% and 50%, respectively
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Uninterruptible power supply system using a dual converter in quasi-resonant mode
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Uninterruptible Power Supply (UPS) systems have become a standard to protect electronic devices such as servers and host computers. Also, the energy supply of whole buildings is linked with large UPS systems to ensure a steady power flow. Two system configurations are widely used which differ in price and their ability to protect very sensitive load. This thesis illustrates an analytical examination of all existing systems and concludes with the finding of new configurations with increased efficiency and reduced costs. A dual converter is proposed as the heart of the new UPS system. This converter links the necessary two sources of the UPS through a common transformer. The transformer operates at a high frequency which is enabled due to the resonant switching technique used. The results of this paper were achieved using mathematical analysis, electrical and electro-magnetic simulation as well as by experiments carried out on the self designed circuit boards in the laboratory. These boards were built in a modular way to enable series testing and thereby optimise the dimensioning of the system.This work is the result of a collaborative project between the BRUNEL UNIVERSITY WEST LONDON,U.K. and the FACHHOCHSCHULE FUR
TECHNIK ESSLINGEN, GERMANY
Doctor of Philosophy
dissertationCommunication surpasses computation as the power and performance bottleneck in forthcoming exascale processors. Scaling has made transistors cheap, but on-chip wires have grown more expensive, both in terms of latency as well as energy. Therefore, the need for low energy, high performance interconnects is highly pronounced, especially for long distance communication. In this work, we examine two aspects of the global signaling problem. The first part of the thesis focuses on a high bandwidth asynchronous signaling protocol for long distance communication. Asynchrony among intellectual property (IP) cores on a chip has become necessary in a System on Chip (SoC) environment. Traditional asynchronous handshaking protocol suffers from loss of throughput due to the added latency of sending the acknowledge signal back to the sender. We demonstrate a method that supports end-to-end communication across links with arbitrarily large latency, without limiting the bandwidth, so long as line variation can be reliably controlled. We also evaluate the energy and latency improvements as a result of the design choices made available by this protocol. The use of transmission lines as a physical interconnect medium shows promise for deep submicron technologies. In our evaluations, we notice a lower energy footprint, as well as vastly reduced wire latency for transmission line interconnects. We approach this problem from two sides. Using field solvers, we investigate the physical design choices to determine the optimal way to implement these lines for a given back-end-of-line (BEOL) stack. We also approach the problem from a system designer's viewpoint, looking at ways to optimize the lines for different performance targets. This work analyzes the advantages and pitfalls of implementing asynchronous channel protocols for communication over long distances. Finally, the innovations resulting from this work are applied to a network-on-chip design example and the resulting power-performance benefits are reported
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