The Blocks' Compatibleness Test Data Compression Using Internal Scan Chains

A test data compression scheme, based on blocks' compatibility between responses and test vectors, is presented. In the scheme, don't care bits in test vectors can be increased by using the blocks' compatibility between responses and test vectors. The length of encoding LFSR is reduced without any additional test vectors, and therefore the test set can be compressed. The decompression structure needs only an LFSR and a simple control circuit. Experimental results indicate that the proposed scheme provides a higher ratio of test data compression than the other test data compression strategies such as the syncopation method, the hybrid coding strategy, and the FDR coding, with little hardware overhead.