A Test Data Compression Scheme for Reducing Power Based on OLELC and NBET

摘要

A new test data compression scheme is introduced. This scheme encodes the test data provided by the core vendor, using a new and very effective compression scheme based on OLEL coding and neighboring bit-wise exclusive-or transform (OCNBET). Codeword is divided into two parts according to the position: odd bits and even bits. The odd bits of codeword are used to represent the length of runs and the even bits of codeword are used to represent whether a run is finished. Furthermore, a neighboring bit-wise exclusive-or transform is introduced to increase the probability of runs of Os in the transformed data, so significant compression improvements and power efficient compared with the already known schemes are achieved. A simple architecture is proposed for decoding the compressed data on chip. Its hardware overhead is very low and comparable to that of the most efficient methods in the literature. Experimental results for the six largest ISCAS-89 benchmark circuits show that the proposed scheme is obviously better than the already known schemes in the aspects of compression ratio, power and the decompression structure.