Electronic Design Automation

3.5.2. Circuits for test response compaction

Test response compaction is performed at the outputs of the scan chains. The purpose is to reduce the amount of test response that needs to be transferred back to the tester. Although test stimulus compression must be lossless, test response compaction can be lossy. A large number of different test response compaction schemes and associated (response) compactors have been presented in the literature [Wang 2006a]. The effectiveness of each compaction scheme and the chosen compactor depends on its ability to avoid aliasing and tolerate unknown test response bits or X's. These schemes can be grouped into three categories: (1) space compaction, (2) time compaction, and (3) mixed space and time compaction ...