Abstract: Increase the effective data rate of high-speed data communication. It has a memory unit, a reception signal line, and a transmission signal line capable of communicating with an external device via a control circuit and an equalizer, controllers for controlling transmission and reception of signals to and from the external device, and a correction coefficient associated with an identification information and the identification information of the external device. The control circuit sets the correction coefficient associated with the identification information to the equalizer.

Abstract: Increase the effective data rate of high-speed data communication. It has a memory unit, a reception signal line, and a transmission signal line capable of communicating with an external device via a control circuit and an equalizer, controllers for controlling transmission and reception of signals to and from the external device, and a correction coefficient associated with an identification information and the identification information of the external device. The control circuit sets the correction coefficient associated with the identification information to the equalizer.

Abstract: A power feeding device coupled to a power receiving device via a USB cable having an authentication chip includes: a communication circuit communicating with the power receiving device; an authentication circuit executing an authentication process with the authentication chip; a power supply circuit supplying power to a power supply line in the USB cable; and a control circuit controlling the power supply circuit based on the authentication process and power supply information of the power feeding device from the communication circuit. When the authentication process between the authentication chip and the authentication circuit succeeds, the control circuit instructs to supply requested voltage and current to the power supply line. When the authentication process between the authentication chip and the authentication circuit fails, the control circuit instructs to supply to the power supply line the requested voltage and a restricted current that restricts the requested current.