Syndrome signature in output compaction for VLSI BIST

An output compaction method, called syndrome signature, is proposed herein. It is particularly well-suited for exhaustive testing of VLSI circuits and is based on the idea originally developed by Savir for syndrome testing. A syndrome is the normalized number of 1´s realized by a function under exhaustive application of all possible input patterns. Given an n-input combinational circuit, a syndrome signature is defined by an (n+1)-element vector consisting of the primary syndrome of the function F and n other subsyndromes corresponding to the subfunctions obtained by setting i^th variable in F, equal to 0 or 1. A multiple output syndrome signature is also discussed, which preserves all the desirable properties of the conventional single-output circuit response analyzers. The proposed technique is implemented on various combinational circuits and the results look very promising