Provided is a memory system and a method that can initialize a data channel at a high speed without the need to increase the number of pins in a semiconductor memory device, and not requiring a circuit to perform an initialization. The memory system includes a memory module equipped with a plurality of semiconductor memory devices; a memory controller controlling the semiconductor memory devices; and a data channel and a command/address channel connected between the plurality of semiconductor memory devices and the memory controller, wherein read latencies and write latencies of the plurality of semiconductor memory devices are controlled by the memory controller.