A method of operating a storage device including first and second memory devices and a memory controller, which are connected to a single channel, the method including: transmitting first data output from the first memory device to the memory controller through a data signal line in the single channel; and transmitting a command to the second memory device through the data signal line while the memory controller receives the first data, wherein a voltage level of the data signal line is based on the command and the first data of the first memory device is loaded on the data signal line, and the first data and the command are transmitted in both directions of the data signal line.