There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

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.

Embedded deterministic test

The increased operating frequencies, geometry shrinking and power supply reduction that accompany the process of very deep submicron scaling, affect the reliable operation of very deep submicron ICs. The effects of various noise sources are becoming of great concern. In particularly, it is predicted that single event upsets induced by alpha particles and cosmic radiation will become a cause of unacceptable error rates in future very deep submicron and nanometer technologies. This problem, concerning in the past more often parts used in space, will affect future ICs at sea level. This challenging problem has to be solved otherwise technological progress will be blocked soon. Thus, fault tolerant design is becoming necessary, even for commodity applications. But economic constraints of commodity applications exclude the use of traditional, high-cost fault tolerant techniques. This work uses time redundancy techniques to derive low cost soft-error tolerant implementations for logic networks.

Time redundancy based soft-error tolerance to rescue nanometer technologies

VLSI Test Principles and Architectures: Design for Testability (Systems on Silicon)

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

https://users.ece.utexas.edu/~touba/research/dt06.pdf

Survey of Test Vector Compression Techniques

Excessive switching activity during scan testing can cause average power dissipation and peak power during test to be much higher than during normal operation. This can cause problems both with heat dissipation and with current spikes. Compacting scan vectors greatly increases the power dissipation for the vectors (generally the power becomes several times greater). The compacted scan vectors often can exceed the power constraints and hence cannot be used. It is shown here that by carefully selecting the order in which pairs of test cubes are merged during static compaction, both average power and peak power for the final test set can be greatly reduced. A static compaction procedure is presented that can be used to find a minimal set of scan vectors that satisfies constraints on both average power and peak power. The proposed approach is simple yet effective and can be easily implemented in the conventional test vector generation flow used in industry today.

https://users.ece.utexas.edu/~touba/research/vts00a.pdf

Static compaction techniques to control scan vector power dissipation

A novel test vector compression/decompression technique is proposed for reducing the amount of test data that must be stored on a tester and transferred to each core when testing a core-based design. A small amount of on-chip circuitry is used to reduce both the test storage and test time required for testing a core-based design. The fully specified test vectors provided by the core vendor are stored in compressed form in the tester memory and transferred to the chip where they are decompressed and applied to the core (the compression is lossless). Instead of having to transfer each entire test vector from the tester to the core, a smaller amount of compressed data is transferred instead. This reduces the amount of test data that must be stored on the tester and hence reduces the total amount of test time required for transferring the data with a given test data bandwidth.

https://users.ece.utexas.edu/~touba/research/itc98a.pdf

Test vector decompression via cyclical scan chains and its application to testing core-based designs

In this paper, a new paradigm for designing logic circuits with concurrent error detection (CED) is described. The key idea is to exploit the asymmetric soft error susceptibility of nodes in a logic circuit. Rather than target all modeled faults, CED is targeted towards the nodes that have the highest soft error susceptibility to achieve cost-effective tradeoffs between overhead and reduction in the soft error failure rate. Under this new paradigm, we present one particular approach that is based on partial duplication and show that it is capable of reducing the soft error failure rate significantly with a fraction of the overhead required for full duplication. A procedure for characterizing the soft error susceptibility of nodes in a logic circuit, and a heuristic procedure for selecting the set of nodes for partial duplication are described. A full set of experimental results demonstrate the cost-effective tradeoffs that can be achieved.

https://www.pitt.edu/~kmram/publications/itc03.pdf

Cost-effective approach for reducing soft error failure rate in logic circuits

A compression/decompression scheme based on statistical coding is presented for reducing the amount of test data that must be stored on a tester and transferred to each core in a core-based design. The test vectors provided by the core vendor are stored in compressed form in the tester memory and transferred to the chip where they are decompressed and applied to the core. Given the set of test vectors for a core, a statistical code is carefully selected so that it satisfies certain properties. These properties guarantee that it can be decoded by a simple pipelined decoder (placed at the serial input of the core's scan chain) which requires very small area. Results indicate that the proposed scheme can use a simple decoder to provide test data compression near that of an optimal Huffman code. The compression results in a two-fold advantage since both test storage and test time are reduced.

Nur A. Touba

Papers

Survey of Test Vector Compression Techniques

Static compaction techniques to control scan vector power dissipation

Test vector decompression via cyclical scan chains and its application to testing core-based designs

Cost-effective approach for reducing soft error failure rate in logic circuits

Scan vector compression/decompression using statistical coding