A memory module including at least one memory and a memory control circuit to control the at least one memory and to generate an internal operation request including an information regarding internal operation time when the memory module need the internal operation time. The memory control circuit is to transfer the internal operation request to an external device, to receive a first command from the external device in response to the internal operation request and including an information of whether the internal operation time is approved, and to perform the internal operation during the internal operation time based on the first command.