Alternating Run-Length Coding – A Technique for Improved Test Data Compression

Store-and-generate techniques encode a given test set and regenerate the original test set during test with the help of a decoder. They are particularly suitable for IP cores coming with pre-computed test sets, and they also offer a natural option for test resource partitioning, because the encoded test data can be stored either on or off chip. Previous research has focused on run-length coding where the test set is considered as a sequence of runs of zero , each run terminated by a one. This may lead to an inefficient encoding for runs of ones. In this paper a new encoding strategy is proposed to overcome this problem: a test is considered as a sequence of alternating runs of zeros and runs of ones. This way, it can simply be encoded as a sequence of run-lengths. The experimental results for benchmark circuits show that in most cases the proposed scheme can provide better compression ratios than previously proposed approaches.