Diagnosis and Repair of Memory with Coupling Faults

The problem of diagnosis and spare allocation for random-access memory (RAM) with coupling faults is addressed. A number of spare allocation algorithms for RAM with row and column redundancy have recently been proposed. These procedures, however, have been restricted to repairing stuck-at faults. The authors examine both diagnosis and repair of coupling faults in RAMs utilizing spare rows and columns. It is shown that a coupling fault is repaired if its coupling cell is replaced by utilizing a spare row or its coupled cell is replaced by utilizing a spare row or column. By specifying both the coupled cell and coupling cell, the amount of redundancy required to repair a given set of faults may be reduced. A diagnosis procedure for RAM is provided to locate stuck-at faults as well as coupling faults. A graph model is used to describe the repair of coupling faults. A repair procedure has been implemented to allocate rows and columns for repair.