Seiji Kajihara

Bio: Seiji Kajihara is an academic researcher from Kyushu Institute of Technology. The author has contributed to research in topics: Automatic test pattern generation & Fault coverage. The author has an hindex of 25, co-authored 154 publications receiving 2368 citations.

On low-capture-power test generation for scan testing

Abstract: Research on low-power scan testing has been focused on the shift mode, with little or no consideration given to the capture mode power. However, high switching activity when capturing a test response can cause excessive IR drop, resulting in significant yield loss. This paper addresses this problem with a novel low-capture-power X-filling method by assigning 0's and 1's to unspecified (X) bits in a test cube to reduce the switching activity in capture mode. This method can be easily incorporated into any test generation flow, where test cubes are obtained during ATPG or by X-bit identification. Experimental results show the effectiveness of this method in reducing capture power dissipation without any impact on area, timing, and fault coverage.

Low-capture-power test generation for scan-based at-speed testing

Abstract: Scan-based at-speed testing is a key technology to guarantee timing-related test quality in the deep submicron era. However, its applicability is being severely challenged since significant yield loss may occur from circuit malfunction due to excessive IR drop caused by high power dissipation when a test response is captured. This paper addresses this critical problem with a novel low-capture-power X-filling method of assigning 0's and 1's to unspecified (X) bits in a test cube obtained during ATPG. This method reduces the circuit switching activity in capture mode and can be easily incorporated into any test generation flow to achieve capture power reduction without any area, timing, or fault coverage impact. Test vectors generated with this practical method greatly improve the applicability of scan-based at-speed testing by reducing the risk of test yield loss

Invisible delay quality - SDQM model lights up what could not be seen

Abstract: The quality of delay testing focused on small delay defects is not clear when traditional fault models are used. We therefore evaluated the feasibility of using the statistical delay quality model (SDQM) - which reflects fabrication process quality, design delay quality, test timing accuracy, and test pattern quality - by using a commercial automatic test program generation (ATPG) tool to apply it to a large data set. The SDQM can also provide a measure predicting the defect level of a chip, and by simulating test patterns we show experimentally here that this measure can be calculated within a reasonable CPU time when using a reasonable amount of memory. Because we found when using SDF information to calculate path lengths accurately that the transition test patterns are not good at detecting small delay defects in long paths, a new test algorithm that detects small delay defects should be developed

XID: Don't care identification of test patterns for combinational circuits

Abstract: Given a test set for stuck-at faults of a combinational circuit or a full-scan sequential circuit, some of the primary input values may be changed to the opposite logic values without losing fault coverage. We can regard such input values as don't care (X). In this paper, we propose a method for identifying the X inputs of test vectors in a given test set. While there are many combinations of X inputs in the test set generally, the proposed method finds one including as many X inputs as possible, by using fault simulation and procedures similar to implication and justification of automatic test pattern generation (ATPG) algorithms. Experimental results for ISCAS benchmark circuits show that approximately 69% of the inputs of uncompacted test sets could be X on the average. Even for highly compacted test sets, the method found that approximately 48% of inputs are X.

A new ATPG method for efficient capture power reduction during scan testing

Abstract: High power dissipation can occur when the response to a test vector is captured by flip-flops in scan testing, resulting in excessive JR drop, which may cause significant capture-induced yield loss in the DSM era. This paper addresses this serious problem with a novel test generation method, featuring a unique algorithm that deterministically generates test cubes not only for fault detection but also for capture power reduction. Compared with previous methods that passively conduct X-filling for unspecified bits in test cubes generated only for fault detection, the new method achieves more capture power reduction with less test set inflation. Experimental results show its effectiveness.

Embedded deterministic test

Abstract: This paper presents a novel test-data volume-compression methodology called the embedded deterministic test (EDT), which reduces manufacturing test cost by providing one to two orders of magnitude reduction in scan test data volume and scan test time. The presented scheme is widely applicable and easy to deploy because it is based on the standard scan/ATPG methodology and adopts a very simple flow. It is nonintrusive as it does not require any modifications to the core logic such as the insertion of test points or logic bounding unknown states. The EDT scheme consists of logic embedded on a chip and a new deterministic test-pattern generation technique. The main contributions of the paper are test-stimuli compression schemes that allow us to deliver test data to the on-chip continuous-flow decompressor. In particular, it can be done by repeating certain patterns at the rates, which are adjusted to the requirements of the test cubes. Experimental results show that for industrial circuits with test cubes with very low fill rates, ranging from 3% to 0.2%, these schemes result in compression ratios of 30 to 500 times. A comprehensive analysis of the encoding efficiency of the proposed compression schemes is also provided.

Survey of Test Vector Compression Techniques

Abstract: Test data compression consists of test vector compression on the input side and response, compaction on the output side This vector compression has been an active area of research This article summarizes and categories these techniques The focus is on hardware-based test vector compression techniques for scan architectures Test vector compression schemes fall broadly into three categories: code-based schemes use data compression codes to encode test cubes; linear-decompression-based schemes decompress the data using only linear operations (that is LFSRs and XOR networks) and broadcast-scan-based schemes rely on broadcasting the same values to multiple scan chains

Switching Theory for Logic Synthesis

Abstract: From the Publisher: Switching Theory for Logic Synthesis covers the basic topics of switching theory and logic synthesis in fourteen chapters. Chapters 1 through 5 provide the mathematical foundation. Chapters 6 through 8 include an introduction to sequential circuits, optimization of sequential machines and asynchronous sequential circuits. Chapters 9 through 14 are the main feature of the book. These chapters introduce and explain various topics that make up the subject of logic synthesis: multi-valued input two-valued output function, logic design for PLDs/FPGAs, EXOR-based design, and complexity theories of logic networks. An appendix providing a history of switching theory is included. The reference list consists of over four hundred entries. Switching Theory for Logic Synthesis is based on the author's lectures at Kyushu Institute of Technology as well as seminars for CAD engineers from various Japanese technology companies. Switching Theory for Logic Synthesis will be of interest to CAD professionals and students at the advanced level. It is also useful as a textbook, as each chapter contains examples, illustrations, and exercises.