Controller and operating method for performing read operation to read data in memory device

Abstract

A controller is provided to include a processor reading data from a memory device, and a decoder receiving the data and decoding the data, the data being represented with check nodes and variable nodes. The decoder includes a check unit calculating syndrome values, a calculation unit receiving the decision values of the variable nodes and calculating flipping function values, a setting unit receiving the flipping function values and generating a candidate vector by dividing the flipping function values into groups and selecting at least some maximum values from the groups, the setting unit setting a flipping function threshold value, and a flipping unit receiving the flipping function threshold value, comparing the flipping function values of the variable nodes with the flipping function threshold value, and flipping a decision value of a target variable node having a greater flipping function value than the flipping function threshold value.