MISR
Beginner
A small circuit that boils a huge stream of test results down to one short fingerprint.
Novice
Multiple-input signature register: an LFSR that also mixes in many output bits every clock, folding a whole test’s worth of results into one short value (a signature) that is compared once at the end with the expected value.
Expert
Linear, so the final signature is the XOR of each input stream’s polynomial remainder. A single unknown (X) input makes the signature unknown, so MISR-based BIST and compaction need X-free responses or masking.