A Self-Testing Dynamic RAM Chip

A novel approach to making very large dynamic RAM chips self-testing is presented. It is based on two main concepts on-chip generation of regular test sequences with very high fault coverage, and concurrent testing of storage-cell arrays to reduce overall testing time. The failure modes of a typical 64K RAM employing one-transistor cells are analyzed to identify their test requirements. A comprehensive test generation algorithm that can be implemented with minimal modification to a standard cell layout is derived. The self-checking peripheral circuits necessary to implement this testing algorithm are described, and the self-testing RAM is briefly evaluated.