US Patent 9761308 Systems and methods for adaptive read level adjustment

Reading requested data from flash memory using a first read level voltage. A number of first bit-value errors and a number of second bit-value errors is determined from the read requested data. An error ratio of the number of first bit-value errors and the number of second bit-value errors is compared to an error-ratio range. The first level voltage is adjusted based on the comparison of the error ratio to the error-ratio range.