The main approaches to the formation of competence in the field of diagnostics of circuits based on FPGA

Abstract

This work is devoted to the questions of diagnostics and control of primitive machines (combinational circuits), described by Boolean equations in “Theory of machines”, which are the theoretical foundation for formulating and solving problems in the field of computer science. A classic application of these provisions is the development of models of computing systems hardware. Along with the classical application this theory is widely used for modeling and the creation of important software. Well-known scientist in the field of Informatics Brian Randall, speaking at a conference, said: “I remember Doug Ross from Soft Tech Company, many years ago saying that 80 or even 90% of computer science in the future will be based on the theory of finite automata”. The aim of the study is the construction of diagnostic tests for combinational circuits with a check for constant error. The problem of diagnosis is relevant primarily to verify the functioning of large integrated circuits, as design errors are unpredictable and can be equivalent to errors of high multiplicity. In addition, these methods are necessary for diagnosis of such circuits during their manufacture and operation. The determination of a technical condition of diagnostic object consists in submitting to it a sequence of input actions and subsequent analyze of the degree of matching between the output actions and the algorithm, which the diagnostic object must implement. The input sequences can be either working sequence of impacts, i.e. impacts coming to the object in the process of its operation as intended, or a sequence of specially generated test actions. In the former case it is functional stimulus and in the second case it is test stimulus. The set of tools and the diagnostic object constitute a system of technical diagnostics (STD). Requirements for STD greatly depend on the stage of “life project” (design, manufacture or operation) during which the technical diagnostics is carried out. Checking the correctness of the design is to determine the compliance of functional circuit, made in the required element base with the original design requirements. Technical diagnosis of circuits that are performed at various stages of their production is an integral part of the technological process of their manufacture. Therefore, there are strict requirements for the duration of the diagnosis that provides the required reliability of the results. The requirements for the reliability of the results, duration, frequency of diagnosis, performed during the operation, may vary within wide limits depending on the purpose of STD and mode of its application [1, 2, 3, 5]. During the research the authors obtained the ways to generate test suites that provide a single view in one direction (no reverse lookup) to determine the fault. At the same time such STD parameters as the required accuracy of the results of technical diagnosis, allowable frequency and duration of diagnosis, a valid memory for storing diagnostic information for the STD for different purposes can vary within a wide range. Thus, the use of methods for test sets’ construction allows to obtain the algorithm of generation of all the necessary information for conducting diagnostic tests using the analytical form of the output function. The authors formulated conditions sufficient for the generation of the diagnostic sequence for the detection of constant errors in the combinational circuits on the base of the analytical form. The issues outlined above are relevant for teaching in technical universities and widely used in the creation of the operating devices on the base of programmable logical integrated circuits (FPGA) and basic matrix crystals (BMC).