13189402

Paragraph Number

289

Similarly, in certain embodiments, the direction module 406 determines that a read voltage threshold 662 deviates toward a smaller read voltage in response to a difference between a read bias for the lower pages and a known bias for the lower pages indicating that storage cell values for the LSBs have transitioned from a binary zero to a binary one. For an LSB to transition from a binary zero to a binary one, a read voltage for a multi-level storage cell using the encoding model of FIG. 6C must drift from either an L3 or L2 state to an L1 or L0 state, indicating that one or more of the read voltage thresholds 662 should be decreased, to place the read voltage back in the original L3 or L2 state. In certain embodiments, a deviation across multiple states may be unlikely, and deviations detectable using LSBs may be between the L1 and L2 states, indicating a clear direction of deviation in either direction.

Added by DJM 3 2021