Test data compression scheme based on variable-to-fixed-plus-variable-length coding

A test data compression scheme based on Variable-to-Fixed-Plus-Variable-Length (VTFPVL) coding is presented, by using which the test data can be compressed efficiently. In this scheme, code words are divided into fixed-length head section and variable-length tail section. In order to attain further compression, the highest bit of the tail is omitted from the code words, because all of the highest bits in the tail section of the code words are the same as 1. A special shift counter is also used, which further eases the control circuit. Experimental results of the MinTest fault sets which are part of ISCAS-89 benchmark circuits show that the proposed scheme is obviously better than traditional coding methods in the compression ratio and the implementation of decompression, such as Golomb, FDR, VIHC, v9C coding.