Chinese Journal of Computers   Full Text
Title	A Scheme of LFSR Reseeding Based on Dividing Parity Bits of Test Cubes
Authors	LIANG Hua-Guo1) ZHAN Kai-Hua1) JIANG Cui-Yun2) YI Mao-Xiang2)
Address	1)(School of Computer and Information, Hefei University of Technology, Hefei 230009) 2)(School of Science, Hefei University of Technology, Hefei 230009)
Year	2007
Issue	No.10(1689—1695)
Abstract &   Background	Abstract A novel scheme of LFSR reseeding based on dividing some test cubes with many specified bits is presented in this paper. As the numbers of specified bits of test cubes vary widely and the specified bits always appear consecutively in a test cube, the proposed scheme divides the test cube with many specified bits by separating odd bits from even bits. The cube is divided into two new cubes each of which has almost half of specified bits of the original cube. It can reduce the largest number of specified bits in any test cube in the test set. Thus it can reduce the degree of LFSR encoding and increase the encoding efficiency. Only a single LFSR is used for decompressing the LFSR seeds and combining the divided cubes. Its control circuit is simple. Thus the hardware overhead is less than LFSR reseeding alone. Compared with the previous schemes, the proposed scheme can increase the encoding efficiency with less hardware overhead. And the LFSR seeds are same length so the community protocol for transmitting test data with the ATE is simple. keywords LFSR encoding; reseeding; dividing of parity bits; test data compression; mixed-mode test background As the size and the complexity of systems on a chip continue to grow, test data volume has increased dramatically. In order to apply the large volume of test data to a chip under test, the automatic test equipment (ATE) requires large memory storage and high bandwidth, so resulting in test cost increases. To reduce test cost，BIST(built-in self-test) and test resource partition techniques were proposed. For examples: multiple-polynomial LFSR reseeding, reseeding of folding counters, LFSR reseeding using variable-length seeds and dynamic LFSR scheme. In this paper, a new scheme based on LFSR reseeding is presented. By separating parity bits of a test cube, the cube is divided into two new cubes each of which has almost half of specified bits of the original cube. Dividing some cubes with large number of specified bits can reduce the degree of LFSR encoding. Compared with the previous schemes, the proposed scheme can increase the encoding efficiency with less hardware overhead. This work is supported in part by the National Natural Science Foundation of China (No. 90407008, No. 60633060) and the Natural Science Foundation of Anhui Province of China under grant No.050420103. The research topic mainly develops BIST and test data compression techniques so as to reduce test cost. In the research group, lots of researches have been achieved to solve these problems and many efficient BIST and test data compression schemes have been proposed, for example: 1. A deterministic BIST scheme based on reseeding of folding counters. 2. LFSR reseeding based on syncopation of some test patterns.