Abstract: A signal state detection circuit of a data transfer control device notifies a processing of results detected by a line state detection circuit or a power supply line detection circuit by using an interrupt signal. The processing sets a state command corresponding to a state of a transition destination judged based on the notified detection results in a control register of a state controller. A state command decoder decodes the state command set in the control register and generates a control signal. A signal line control circuit controls a signal state of at least one of signal lines formed of data signal lines (D+ and D−) and power supply lines (VBUS and GND) based on the control signal.

Abstract: When an electronic instrument Q is in normal operating mode and set to be slave, power from a rechargeable battery or an external power source is supplied to a data transfer control circuit, and when the electronic instrument Q is in charge mode and set to be slave, power from VBUS is supplied thereto to charge a rechargeable battery. When an external power source can be used in charge mode, power from the external power source is supplied to the rechargeable battery instead of from VBUS. When an electronic instrument P is in normal operating mode and set to be master, power from a rechargeable battery or an external power source is supplied to the data transfer control circuit and the electronic instrument Q; and when the electronic instrument P is in charge mode and set to be master, power from the rechargeable battery or the external power source is supplied to the electronic instrument Q through the VBUS in order to charge a rechargeable battery of the electronic instrument Q.