According to an embodiment, the electronic device may determine whether there is a packet exchange with an external device (e.g., the electronic device 100 of FIG. 3) for a predetermined time. When there is no packet exchange with an external device for the predetermined time, the electronic device may enter the power saving mode. The packet may be, for example, a start of frame (SOF) packet.

According to an embodiment, the power saving mode may be an L1 or L2 mode. Hereinafter, the power saving mode will be exemplified as the L2 mode. When there is no SOF packet for a predetermined time, the electronic device may recognize that the communication connection with the external device is in an inactive state and enter the L2 mode. According to an embodiment, the electronic device may identify entry to the power saving mode and transmit a message related to the power saving mode to the external device 200. The power saving mode will be described later.

In operation 603, the electronic device (the processor, the USB controller 111, or the identification circuit 130) may identify a change in the ID of the external device 200 during data communication with the external device 200. For example, the electronic device may detect an ID (e.g., a second resistance value) having a different value from the ID (e.g., a first resistance value) detected in operation 601, through the identification circuit 130. The change in the ID may correspond to a change in a resistance value connected to a pogo ID pin of the first input/output interface (e.g., the first input/output interface 140 of FIG. 1). According to an embodiment, the external device 200 may change the ID in response to a message associated with the power saving mode of the electronic device.