A method of operating a memory controller, memory devices including a master memory device and slave memory devices, a back channel bus coupling the master memory device to the slave memory devices and a channel coupling the memory controller to the memory devices is provided as follows. A memory command is received by the memory devices from the memory controller. An internal command is generated and outputted by the master memory device. The internal command is received by the slave memory devices. The internal command is transmitted to the slave memory devices through the back channel bus.