| 摘要 |
PROBLEM TO BE SOLVED: To provide an electronic apparatus capable of notifying a host about the occurrence of an event from a device without assuming a status response request from the host.SOLUTION: The electronic apparatus comprises: a transmission/reception unit for communicating with a host via a USB signal line connected thereto; a pull-up resistor for pulling the USB signal line high in order to have communication speed designation detected by the host; a switch for setting and releasing pull-up; and a control unit capable of switching between a normal mode in which a status response is transmitted in response to a status response request and a power-saving mode to which transition is made from the normal mode when, for a status response request asking whether transition to the power-saving mode is possible, a response is made to the effect that transition to the power-saving mode is possible, the transition occurring after the host has stopped transmitting the status response request. The control unit further clears the pull-up setting when transition from the power-saving mode to the normal mode is caused by an event in the apparatus, makes the host recognize the severance of a connection, resets the released pull-up, makes the host recognize a reconnection, and makes the host restart the transmission of the status response request. |
