• ICROS
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• v.17 no.4
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• pp.35-41
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• 2011

비동기적으로 동작하는 디지털 회로는 동기 순차 회로에 비해서 고속, 저전력 소비 등 여러 가지 장점을 지니기 때문에 현대 디지털 시스템에서 여전히 중요한 요소로 사용되고 있다. 본 기고에서는 비동기 순차 회로에서 발생하는 고장을 진단하고 극복하는 최신 기술을 소개한다. 본 기고에서 주로 다루는 기술은 '교정 제어'로서 피드백 제어의 원리를 이용하여 비동기 순차 회로의 안정 상태를 바꾸는 기법이다. 크리티컬 레이스(critical race), 무한 순환 등 비동기 회로 설계상의 오류를 포함하여 SEU(Single Event Upset), 총이론화선량(TID)에 의한 고장 등 외부 환경에 의해서 발생하는 비동기 회로의 고장을 교정 제어를 이용하여 진단하고 극복하는 기술에 대해서 알아본다.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.9
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• pp.38-48
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• 1998

Generating test patterns for asynchronous sequential circuits remains to be a very difficult problem. There are few algorithms for this problem, and previous works cut feedback loops, and insert synchronous flip-flops in the feedback loops during ATPG. The conventional algorithms are similar to the algorithms for synchronous sequential circuits. This means that the conventional algorithms generate test patterns by modeling asynchronous sequential circuits as synchronous sequential circuits. So, test patterns generated by those algorithms nay not detect target faults when the test patterns are applied to the asynchronous sequential circuit under test. In this paper an algorithm is presented to generate test patterns for asynchronous sequential circuits. Test patterns generated by the algorithm can detect target faults for asynchronous sequential circuits with the minimal possibility of critical race problem and oscillation. And it is guaranteed that the test patterns generated by the algorithm will detect target faults.

• Proceedings of the KIEE Conference
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• 1983.07a
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• pp.237-239
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• 1983

본 논문은 어떤 비동기적인 제어계가 상태 천이도(transition diagram)로 표현되기만 하면 이 입력으로부터 직접 비동기 순차회로를 구성 할 수 있는 알고리즘을 제시하고 있다. 이로써 비동기 회로를 쉽게 하드웨어로 실현 할수 있도록 하였다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.1-10
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• 2008

The problem of controlling asynchronous sequential machines is addressed in this paper. Corrective control means to make behavior of an asynchronous sequential machine equal to that of a given model. The main objective is to develope a corrective controller, especially when a model is given as nondeterministic, or a set of reference models. The structure of corrective control system for asynchronous sequential machines is addressed first, followed by description of nondeterministic models. Then, we propose a method for analyzing reachability of asynchronous machines and nondeterministic models. Proposed methods are demonstrated in an example.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.103-109
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• 2016

Corrective control for asynchronous sequential machines is a novel automatic control theory that compensates illegal behavior or adverse effects of faults in the operation of existent asynchronous machines. In this paper, we propose a scheme of diagnosing and tolerating faults occurring to input channels of corrective control systems. The corrective controller can detect faults occurring in the input channel to the controlled machine, whereas those faults happening in the external input channel cannot be detected. The proposed scheme involves an outer operator which, upon receiving the state feedback, diagnoses a fault and sends an appropriate command signal to the controller for tolerating faults in the external input channel.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.9-17
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• 2010

Corrective control compensates the stable-state behavior of asynchronous sequential machines so that the closed-loop system can be changed in a desirable way. Using corrective control, we present a novel fault tolerance scheme that overcomes permanent faults for asynchronous sequential machines. When a permanent fault occurs to an asynchronous machine, the fault is not recovered forever while the machine is irreversibly stuck in a set of failure states. But, if the machine has control redundancy in the limited behavior range, corrective control can be applied to solve the fault tolerance problem against permanent faults. We present the condition on detecting permanent faults and the existence condition of an appropriate corrective controller. The design procedure for the proposed controller is described in a case study.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.2
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• pp.135-140
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• 2016

Corrective controllers enable fault diagnosis and tolerance for various faults in asynchronous sequential circuits without resort to redesign. In this paper, we propose a static corrective controller in order to decrease the size of the controller. Compared with dynamic controllers, static controllers can be made using only combinational circuits, as they need no inner states. We address the existence condition and design procedures for static corrective controllers that overcome state transition faults. To show the validity and advantage, the proposed controller is applied to an SEU error counter implemented on FPGA.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.399-408
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• 2022

This paper proposes a corrective control system to achieve fault-tolerant control for input/output asynchronous sequential circuits vulnerable to transient faults violating fundamental mode operations. To overcome non-fundamental mode faults occurring in transient transitions of asynchronous sequential circuits, it is necessary to determine the end of unauthorized state transitions caused by the faults and to stably take the circuit from the faulty state to a desired state that is output equivalent with the normal next stable state. We address the existence condition for a proper output-feedback corrective controller that achieves fault diagnosis and fault-tolerant control for these non-fundamental mode faults. The corrective controller and asynchronous sequential circuit are implemented on field-programming gate array to demonstrate the synthesis procedure and applicability of the proposed control scheme.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.4
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• pp.39-48
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• 2009

Asynchronous sequential machines, or clockless logic circuits, have several advantages over synchronous machines such as fast operation speed, low power consumption, etc. In this paper, we propose a novel robust controller for input/output asynchronous sequential machines with uncertain state transitions. Due to model uncertainties or inner failures, the state transition function of the considered asynchronous machine is not completely known. In this study, we present a formulation to model this kind of asynchronous machines ana using generalized reachability matrices, we address the condition for the existence of an appropriate controller such that the closed-loop behavior matches that of a prescribed model. Based on the previous research results, we sketch design procedure of the proposed controller and analyze the stable-state operation of the closed-loop system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.11-19
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• 2008

The problem of controlling asynchronous sequential machines is addressed in this paper Corrective control means to make behavior of an asynchronous sequential machine equal to that of a given model. The main objective is to develope a corrective controller, especially when a model is given as nondeterministic, or a set of reference models. We first review representation of nondeterministic models and model matching problems with nondeterministic models, which are presented in the companion paper. We then propose necessary and sufficient conditions for the existence of corrective controllers and describe their design procedure. To show the applicability, the proposed control scheme is demonstrated in an example.