Co-optimization for test data compression and testing power based on variable-tail code

We present a novel code: Variable-Tail code to compress the test data, which is proved to be better than the Golomb code. An efficient reordering algorithm(ERA) is proposed to optimize the distribution of run-lengths in the test data in order to improve the compression effectiveness. On other hand, since the power during testing is always higher than the normal functional mode, the power dissipated in the CUT must be reduced during testing which is omitted previously. The analysis and experiments have demonstrated that our ERA can significantly reduce the total testing power and average power dissipated in the CUT with no hardware are penalty.