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# Matrix Chain for Chain Defect Diagnose

IP.com Disclosure Number: IPCOM000242832D
Publication Date: 2015-Aug-21
Document File: 4 page(s) / 104K

## Publishing Venue

The IP.com Prior Art Database

## Abstract

This paper discusses a method for pinpointing multiple chain defects with Matrix Chain structure. Matrix chain structure is the chains tha have multiple scan inputs and multiple scan outputs. With matrix chain we can locate the chain defects accurately by changing the direction of chain data flow.

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Matrix Chain for Chain Defect Diagnose

# Abstract:

This paper discusses a method for pinpointing multiple chain defects with Matrix Chain structure.  Matrix chain structure is the chains tha have multiple scan inputs and multiple scan outputs. With matrix chain we can locate the chain defects accurately by changing the direction of chain data flow.

## 1.   Background

Scan test is becoming more and more popular for detecting defects in integrated circuits, but we often meet problems of how to debug chain defects because once there is one defect on a chain, all the outputs of the chain will be same, so it is difficult to pinpoint.  While there are some workarounds, they are have difficulty locating multiple defects accurately when the defects are on the same chain.

## 2.   Scan Cell Structure

As Fig.1 shows, compared to normal scan flip-flop, the flip-flop used in matrix chain has two scan inputs, one is SDI_H and the other is SDI_V.  Besides scan inputs, there is another control signal used to select SDI_H and SDI_V.

Fig. 1 Scan Cell Structure

## 3.   Matrix Chain Structure

Fig. 2 shows the basic structure of Matrix Scan Chain. It looks like a matrix, and it has two directions of scan flow. One is horizontal, from left to right, as normal one; the other is vertical, from top to down, as new one. The flow direction is decided by the control signal, MATRIX_SEL in Fig. 1.

Fig. 2 Basic Matrix Chain Structure

## 4.   How to locate multiple defects

If we get mismatches when we do a chain test, we could conclude that there are defects on the chains. Suppose there are two defects on the same chain, it is a harder assumption, as shown in Fig.3, where the dash block are the cells which have defects. Here we suppose the two defects are both stuck-1 for...