XWRC: externally-loaded weighted random pattern testing for input test data compression

This paper presents an input test data compression scheme that combines the advantages of weighted pseudorandom testing techniques and LFSR reseeding. The scheme requires low area overhead and the compression achieved is not limited by the LFSR reseeding bounds. The test data storage requirements of both the static and dynamic versions of the proposed scheme are lower than previously published results. The total numbers of test patterns that need to be applied are much lower than that for any weighted pseudorandom testing or hybrid BIST scheme. Further, the method provides an easy way to trade off between test application time and test data compression. The static version of the scheme can be easily implemented without any modification to the current test generation flow while the dynamic version can be used if the ATPG can be modified. Experimental results on a large industry design show that over 100times compression is achievable by the proposed scheme