Recursive Pseudo-Exhaustive Two-Pattern Generation

Pseudo-exhaustive pattern generators for built-in self-test (BIST) provide high fault coverage of detectable combinational faults with much fewer test vectors than exhaustive generation. In (
n
,
k
)-adjacent bit pseudo-exhaustive test sets, all 2
k
binary combinations appear to all adjacent
k
-bit groups of inputs. With recursive pseudoexhaustive generation, all (
n
,
k
)-adjacent bit pseudoexhaustive tests are generated for
k
¿
n
and more than one modules can be pseudo-exhaustively tested in parallel. In order to detect sequential (e.g., stuck-open) faults that occur into current CMOS circuits, two-pattern tests are exercised. Also, delay testing, commonly used to assure correct circuit operation at clock speed requires two-pattern tests. In this paper a pseudoexhaustive two-pattern generator is presented, that recursively generates all two-pattern (
n
,
k
)-adjacent bit pseudoexhaustive tests for all
k
¿
n
. To the best of our knowledge, this is the first time in the open literature that the subject of recursive pseudoexhaustive two-pattern testing is being dealt with. A software-based implementation with no hardware overhead is also presented.