An interface system connectable to a host and configured to receive and transmit data from and to the host, the system comprising: a receiver configured to receive a first clock and serial data from the host; a first clock generator including a first voltage controlled oscillator (VCO) and configured to generate a second clock on the basis of the first clock; a second clock generator including a second voltage controlled oscillator (VCO) and configured to generate a third clock on the basis of the serial data; a sampling circuit configured to sample reception data on the basis of the third clock and the serial data; a transmitter configured to transmit transmission data to the host on the basis of the second clock; and a controller configured to control a first state where the first and second clock generators are in an operating state and a second state where the first and second clock generators are in a non-operating state, wherein the first clock and the serial data are supplied to the receiver in the first state and are not supplied to the receiver in the second state, and the controller is further configured to, in a first recovery mode, start sampling of the reception data or transmitting of the transmission data to the host after a certain period of time after confirming a transition from the second state to the first state, and not transmit a response indicative of establishment of synchronization of the second and third clocks to the host; characterized in that : the first clock generator includes a control voltage memory unit configured to store a control voltage value corresponding to a voltage controlling the first voltage controlled oscillator (VCO, 244) as an initial control voltage value when the frequency of the second clock is locked in the first state, and to apply a voltage corresponding to the stored initial control voltage value to the first voltage controlled oscillator (VCO) in the first recovery mode. a receiver configured to receive a first clock and serial data from the host; a first clock generator including a first voltage controlled oscillator (VCO) and configured to generate a second clock on the basis of the first clock; a second clock generator including a second voltage controlled oscillator (VCO) and configured to generate a third clock on the basis of the serial data; a sampling circuit configured to sample reception data on the basis of the third clock and the serial data; a transmitter configured to transmit transmission data to the host on the basis of the second clock; and a controller configured to control a first state where the first and second clock generators are in an operating state and a second state where the first and second clock generators are in a non-operating state, wherein the first clock and the serial data are supplied to the receiver in the first state and are not supplied to the receiver in the second state, and the controller is further configured to, in a first recovery mode, start sampling of the reception data or transmitting of the transmission data to the host after a certain period of time after confirming a transition from the second state to the first state, and not transmit a response indicative of establishment of synchronization of the second and third clocks to the host; characterized in that : the first clock generator includes a control voltage memory unit configured to store a control voltage value corresponding to a voltage controlling the first voltage controlled oscillator (VCO, 244) as an initial control voltage value when the frequency of the second clock is locked in the first state, and to apply a voltage corresponding to the stored initial control voltage value to the first voltage controlled oscillator (VCO) in the first recovery mode. <EOS>