Redundancy programming using addressable scan paths to reduce the number of required fuses

摘要

A system and method are disclosed which provide the capability of repairing an optimum number of defective memory segments, such as RAM segments, in order to minimize the amount of unused repairing circuitry, such as fuses used for repairing defects within the memory. A preferred embodiment of the present invention provides a RAM block implemented such that the number of fuses required for repairing defects therein is proportional to the optimum number of defective segments capable of being repaired. A preferred embodiment allows for repairing an optimum number of defective segments, while being capable of repairing any of the segments (up to the optimum number) by mapping repair data to an appropriate defective segment. A preferred embodiment provides a repairable RAM block comprising multiple segments of RAM memory cells that are each repairable, a state machine capable of generating repair data for repairing one or more defective segments, a scan address machine capable of generating data identifying one or more defective segments, and a mapping circuitry for mapping the generated repair data of the state machine to the one or more defective segments specified by the scan address machine. Accordingly, by providing the capability of mapping generated repair data to any one of the segments of RAM that is detected as being defective, a preferred embodiment enables repairing an optimum number of defective segments, without being required to provide sufficient circuitry for repairing every segment of RAM.