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 Cidepends on a fixed group of cells called the neighborhood of Ci. 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.