Diagnostic Signature Comparison Register with built-in Self Test and Self Check

Introduction

In an electronic system Printed Circuit Board(PCB) is an important component. During the operation of the system over a period of time, fault develops in the PCB due to short-circuiting or open circuiting. For continuous and satisfactory operation of electronic system, testing (for detection), diagnosis (for location) of fault in the system followed by repair of the fault is very much essential. The known method for testing and diagnosis of the fault is by a system, which is built-in self-test refered herein as BIST. The BIST is invariably based on signature analysis wherein the responses of the sub-circuits or blocks are compacted into signatures. The shortcomings of this method are poor aliasing and diagnostic resolution and increased fault simulation time. In the newly developed method these short-comings are not only eliminated but also features improvement for better functioning of the electronic system.

The newly developed method comprises of Built In Self Test and Self Check refered as BISTSC and the Diagnostic Check Points refered as DCP. The testing and diagnostic process is divided into one or more test sessions and several sub-circuits are tested simultaneously during each session. The test is initiated by giving a control signal to the internal test control circuit of the system. The control signal originates from the diagnostic control circuit in the external tester. During a test session, pseudo-random test inputs are applied to a sub circuit under test and the output responses of the circuit are fed as inputs to the Diagnostic Signature Comparison Register, refered to as DSCR, The DSCR generates a logic HIGH on the Go/No Go output at either a faulty basic point or DCP. The number and time instants of these points are used as diagnostic attributes by which the specific fault or class of faults can be identified.

Salient features:

The present method has advantages such as (i) providing the effective solution for detection followed by identifying the location of fault (ii) testing of faulty system even if it is not working (iii) reduced aliasing and fault simulation time (iv) improved diagnostic resolution (v) can do off-line testing/operate under off-line testing conditions (vi) can be built on the system itself (and hence termed as BISTSC) (vii) no requirement for extra space for installation (viii) compacting the output of the faulty system into signature (instead of the complete response) for detection & identification of fault (ix) better quality and efficiency.

Prospective Users: Printed Circuit Board manufacturers; Electronic equipment/system manufacturers; servicing units; repair shops; R&D laboratories; Inspection & testing agencies, etc.

Keywords: PCB, Signature, Diagnostic Signature

Type of Technology: Device; Software

Status of IPR Protection: Indian Patent Application No. 2085/DEL/98 dated 20.7.1998 with title "A Diagnostic Signature with built-in self test and self check"

Developed by : Prof. Kumar Anshul
Department: Computer Science and Engineering

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