A memory system includes a memory device and a memory controller. The memory device includes a memory cell array configured to store data, a data input and output interface configured to receive a command, an address, and data to be written into the memory cell array from the memory controller, and to output data read from the memory cell array to the memory controller, and a control circuit configured to control the memory cell array to perform an operation in response to receipt of a command while a first control signal is being asserted by the memory controller and receipt of an address subsequent to the command while a second control signal is being asserted by the memory controller.