| 摘要 |
PROBLEM TO BE SOLVED: To provide USB target equipment preventing error operation of the whole system and a through current of a CPU and making a USB connect with USB host equipment. SOLUTION: The CPU 106 cuts a data signal line at a USB signal disconnecting circuit 109 and makes a state that a D+ line is pulled up outside the USB signal disconnection circuit and then it makes the USB host equipment 101 to recognize a pseudo-connection. After detecting presence of a USB data signal output from the USB host equipment, the USB signal disconnection circuit is made in connection state. A VBus detection function 112 detects whether there is supply of a VBus signal from the USB host equipment or not. When there is a VBus signal, a switchover means 110 is controlled so as to connect the D+ line outside the USB signal disconnection circuit for an input port of the CPU when there is a VBus signal, and to connect a port pull down resistance 111 for the input port of the CPU when there is not. COPYRIGHT: (C)2004,JPO
|
