Operating method for memory controller controlling nonvolatile memory device and nonvolatile memroy system

According to an embodiment of the present invention, a memory controller operation method, which is used to control a nonvolatile memory device, includes the steps of: receiving read data from the nonvolatile memory device; performing a first error correction to detect the errors of the received read data and correct the errors; sending dummy data to a host when uncorrected errors are detected based on the first error correction and conducting a second error correction to correct the uncorrected errors during the first error correction. The rest of the read data other than the read data including the uncorrected errors is transmitted to a host while the second error correction is performed.