Apple Inc.
Overcoming saturated syndrome condition in estimating number of readout errors

Abstract:

A controller includes an interface and circuitry. The interface is coupled to multiple memory cells. The circuitry stores a code word in a group of the memory cells, reads the code word using different thresholds to produce first and second readouts, and checks whether approximating each of first and second numbers of readout errors based on syndrome weights is valid. In response to determining that only the approximation of the second number of errors is valid, the circuitry produces a combined readout by replacing a portion of the bits in the second readout with corresponding bits of the first readout, calculates an enhanced syndrome weight for the combined readout and estimates the first number of errors based on the enhanced syndrome weight. The circuitry improves readout performance from at least the group of the memory cells using at least one of the estimated first and second numbers of errors.