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Paragraph Number

153

One method a read scan operation may use is referred to as a valley search operation. "Valley search operation" refers to is a type of read scan operation configured to iteratively test or check a number of candidate read levels around a boundary for a set of memory cells within cell threshold voltage distributions for two adjacent memory states. In certain embodiments, the valley search operation may begin with a current read level or a default read level which may have been set when a storage device is manufactured. Next the valley search operation may apply a candidate read level to determine if the candidate read level resulted in fewer memory cells activating than the current read level. If so, this means that more memory cells will be identified as being programmed to a correct memory state. If not, this means that more memory cells will be erroneously identified as being to one of the adjacent memory states. The valley search operation continues to iterate in this manner changing the candidate read level with each iteration until a read level is identified that results in the fewest number set of memory cells being activated and/or a fewest number of read errors (e.g., lower bit error rate). In this manner, the valley search operation seeks a target candidate read level that provides an optimal read result. The valley search operation gets its name from the iterative process of testing candidate read levels until one is located that aligns with a "valley" between cell threshold voltage distribution curves for two adjacent memory states.

Added by DJM 12 2021