Memory device, host device, memory system, memory device control method, host device control method and memory system control method

A host device to which a connectable device is connectable, comprising:

• an interface that can transmit a command signal via a command/response signal line, transmit a clock signal via a clock signal line, receive a response signal via the command/response signal line, and transmit and receive a data signal via data signal lines at any one signal voltage selected from a first voltage and a second voltage which is lower than the first voltage;
• a regulator that can output the first voltage and the second voltage;
• and
• a host control section, the host control section configured to:
• send a command signal requesting a switching processing for switching the signal voltage to the second voltage to the connectable device, when switching the signal voltage from the first voltage to the second voltage;
• receive a response signal from the connectable device, and thereafter set, when the command/response signal line is at the ground level, the clock signal line at a ground level, and then start processing for switching a voltage outputted by the regulator from the first voltage to the second voltage to switch the voltage to the second voltage within a predetermined time;
• supply the clock signal of the second voltage to the clock signal line after a predetermined time has elapsed since the setting of the clock signal line at the ground level in the switching processing;
• and
• start transmission/reception of signals at the second voltage, when detecting that the data signal lines are not at the ground level.

A system comprising:

• a host device;
• and
• a connectable device which is connectable to the host device,
• the connectable device comprising:
• an interface that can receive a command signal via a command/response signal line, receive a clock signal via a clock signal line, transmit a response signal via the command/response signal line, and transmit and receive a data signal via data signal lines at any one signal voltage selected from a first voltage and a second voltage which is lower than the first voltage;
• and
• a first regulator that can output the first voltage and the second voltage,
• the host device comprising:
• an interface that can transmit the command signal via the command/response signal line, transmit the clock signal via the clock signal line, receive the response signal via the command/response signal line, and transmit and receive the data signal via the data signal lines at any one signal voltage selected from the first voltage and the second voltage;
• and
• a second regulator that can output the first voltage and the second voltage,
• wherein, when switching of the signal voltage from the first voltage to the second voltage is performed,
• the host device transmits the command signal requesting so switching of the signal voltage to the connectable device, and
• the connectable device sends a response signal for notifying that the switching is possible to the host device, and thereafter set the command/response signal line and data signal lines at a ground level, and
• wherein, when the connectable device can switch the signal voltage, after the clock signal is set at a ground level by the host device, the connectable device and the host device start processing for switching voltages outputted by the first regulator and the second regulator from the first voltage to the second voltage,
• the host device supplies, after a predetermined time has elapsed since the setting of the clock signal line at the ground level, the clock signal of the second voltage to the clock signal line,
• the connectable device applies, when detecting that a voltage other than the ground level is applied to the clock signal line, the second voltage to the command/response signal line and the data signal lines, which had been set at the ground level, and
• the host device starts transmission/reception of signals at the second voltage, after detecting that the data signal lines are not at the ground level.

A method of controlling a memory card connectable to a host device, comprising:

• receiving a command signal that requests switching of a signal voltage selected from a first voltage and a second voltage being lower than the first voltage, from the host device via a command/response signal line;
• sending a response signal for notifying that the switching is possible to the host device via the command/response signal line, and thereafter setting the command/response signal line and data signal lines at a ground level;
• applying the switched signal voltage to the command/response signal line and the data signal lines, which had been set at the ground level, to indicate completion of the switching of the signal voltage to the host device;
• and
• starting transmission/reception of signals at the switched signal voltage.