Clearing a watchdog timer every time a processor instructs a transmission of a ping message to a power receiving device

摘要

A controller, which is installed on a power supply device complying with the USB (Universal Serial Bus)-PD (power delivery) specification and controls a power supply circuit for supplying a bus voltage to a power receiving device via a bus line is disclosed. The controller includes an interface circuit, which communicates with the power supply device via the bus line; a processor, which transmits and receives messages to and from the power receiving device by using the interface circuit, determines a voltage level of the bus voltage, and sets the determined voltage level to the power supply circuit; and a watchdog timer, which is cleared whenever the processor executes a ping-related command for transmission or reception of ping messages to or from the power receiving device, wherein an overflow period of the watchdog timer is set to be longer than a period for the ping messages.