Detection oF Pattern-Sensitive Faults in Random-Access Memories

Some formal models for pattern-sensitive faults (PSF's) in random-access memories are presented. The problem of detecting unrestricted PSF's is that of constructing a checking sequence for the memory. An efficient procedure for constructing such a checking sequence is presented. A local PSF is defined as a PSF where the faulty behavior of a memory cell C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> depends on a fixed group of cells called the neighborhood of C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> . Neighborhoods are divided into two classes, open and closed. Test generation methods are described for local PSF's defined on both open and closed neighborhoods. The detection of PSF's when only one memory cell is faulty (single PSF's) is also discussed.