A memory system includes a memory chip, one or more signal lines including a first signal line, and a controller. The controller is connected to the memory chip via the one or more signal lines. The controller is configured to transmit and receive signals via the first signal line in accordance with a first standard under which voltages of communicated signals transition in a first range and with a second standard under which voltages of communicated signals transition in a second range narrower than the first range. The controller is configured to transmit a command to the memory chip via the first signal line in accordance with the first standard, and based on a response to the command from the memory chip, enable communication in accordance with the second standard.