US Patent 7602642 Nonvolatile memory system and associated programming methods

A nonvolatile memory system includes a host system, a memory controller, and a flash memory chip including multi-level flash memory cells. The memory controller includes a backup memory adapted to store a backup copy of previously programmed data from the multi-level flash memory cells when further programming of the multi-level flash memory cells fails. The backup copy of the previously programmed data is used to detect and correct any errors in the previously programmed data before reprogramming the previously programmed data to different multi-level memory cells in the nonvolatile memory system.