Test data compression based on reuse and bit-flipping of parts of dictionary entries

Several dictionary-based input test data compression methods have been proposed for intellectual property (IP) cores testing. To increase the utilization of the dictionary entries some methods are based on the correction of some bits before the loading of the entries into the scan chains. The coordinates of the bits that should be corrected are sent by the automatic test equipment (ATE), hence, the number of corrections should be relatively small. In this paper we propose a new method which is based on the use of an auxiliary dictionary of minor size for storing masks. To this end, we give an algorithm for the suitable selection of the masks so that any one of them is used for on the fly bit-flipping of parts of many dictionary entries, before they are loaded into the scan chains. The efficiency of the proposed method is supported with extensive experimental results.