Electronic Design Automation

3.5.2.2. Sequential compaction

In contrast to a combinational compactor that typically uses XOR gates to compact output responses, a sequential compactor uses sequential logic instead. The sequential compactor can be a time-space compressor or a space-time compressor as described in [Saluja 1983], although the authors only considered output bit streams of 0′s and 1′s. The type of sequential logic to be used for response compaction depends on whether the output responses contain unknown values (X's). A sequential compactor capable of masking off or tolerating these X's is often referred to as an X-tolerant sequential compactor.

3.5.2.2.1. Signature analysis

If X-bounding as described previously has been used such that each output response ...