Fault Location in a Semiconductor Random-Access Memory Unit

A semiconductor random-accessor memory (RAM) unit is a connection of RAM chips, data cable, chip select cable, and address cable so that each storage element can be selected for writing or reading independent of previous writes or reads. The faulty RAM unit is represented by a model consisting of four types of faults: stuck-at-0 or 1 fault on data cable, chip select cable, address cable, and storage elements in RAM chips, and a type of adjacent pattern interference fault in RAM chips. The testing of a RAM unit and locating faults to the RAM chips or wires in the various cables, when the RAM unit is part of a computer system, is considered. A set of six tests has been designed to diagnose the faults in the model. The sequence in which these tests have to be performed is determined. By using this sequence faulty components in a RAM unit are located when at most one type of fault in the model is present.