An operation method performed at a nonvolatile memory device may include receiving a program command and an address from an external device through a data signal (DQ), receiving a specific pattern from the external device through the data signal and a data strobe signal (DQS) synchronized with the data signal in a pattern period, receiving user data from the external device through the data signal and the data strobe signal in a data period, and selectively performing a program operation on the user data or a recovery operation based on a determination of whether the specific pattern matches with a particular pattern. A rising edge or a falling edge of the data strobe signal may be aligned with a left edge or a right edge of a window of the data signal in the pattern period.