Study On Analysis For Testability Based On Multi Signal Model

Testability describes the difficulty of obtaining test information,and it is a design characteristic of a system.Testability of a digital circuit shows in its controllability and observability by computing electric circuit interior nodes' testable measure.But each measure based on circuit's structural model,has error and lacks in circuit's whole appraisal.The testability analysis based on multi-signal model,considering dependence between failure and test,can make accurate assessment for digital,analog and digital-analog circuits and give the overall testability evaluation.However,traditional method equates testability analysis in computing testability indictor,neglecting that it should provide essence for system design and failure diagnosis.Therefore,this article researches in electronic circuit's testability evaluation,consummates concept of testability analysis from feedback loop influence,DFT principle and optimizing test sequence,and proposes a analysis system based on multi-signal model for appraisal system's test characteristic from fault characteristic,testability target,test limitation,DFT and test sequence.1.This paper presents a testability analysis system based on multi-signal model,solving existing problems in analysis of test characteristics.It provides analysis for quantitative evaluation indexes,test limitation caused by feedback loop,guidelines for DFT and test sequence optimization results for fault diagnosis.2.Feedback loop identification algorithm is proposed.Based on depth first search,this algorithm calculates the number and size of fuzzy group caused by the feedback and analyses test limitation.3.Global weight test sequence optimization method is proposed.It achieve fault detection and isolation using global optimization in the minimum cost,reducing test time,test point numbers and test cost greatly.4.This article presents software realization scheme for testability analysis and a software architecture that combines model rendering,data management and algorithm analysis.This software can complete basic functions for testability analysis such as model building,dependency matrix seeking,fault analysis and target seeking and so on.It has friendly user interface,easily operation,strong commonality,accuracy and practical.5.Testability of a data acquisition system has been analyzed.And the result is used to formulate DFT proposal and test sequence optimization plan for this data acquisition system.It shows that testability analysis based on multi-signal model has great significance in analyzing system test characteristics and improving system testability,and provides a theoretical basis for system fault diagnosis.