A memory device includes a control logic circuit, a write data strobe signal divider, a data transceiver, and a memory cell array. The control logic circuit generates a reset signal before a write data strobe signal provided from a memory controller starts to toggle. The write data strobe signal divider generates internal write data strobe signals that toggle depending on toggling of the write data strobe signal, the internal write data strobe signals toggling with different phases, respectively. The control logic circuit initializes the internal write data strobe signals to given values in response to the reset signal. The data transceiver receives write data provided from the memory controller based on the internal write data strobe signals. The memory cell array stores the received write data.