Method of and device for detecting cable connection

Abstract

The detector includes a plug for connecting a personal computer through a cable, a battery power supply which provides a constant power supply, and an MCU which receives a specific potential from the personal computer when the latter is connected.

What is claimed: 
     
         1 . A USB device comprising:
 a central processing unit;   a USB function circuit;   a connection detection circuit;   a battery; and   terminals that couple with a host system, wherein the terminals includes that two are data terminals, a reference voltage terminal, and a power supply voltage terminal,   wherein the battery supplies an operation voltage for the central processing unit, the connection detection circuit detects a voltage level of the power supply voltage terminal and notifies the central processing unit of a detection result, and the central processing unit determines whether to issue an enable signal to the USB function circuit in accordance with detection result.   
     
     
         2 . The USB device according to  claim 1 , wherein the connection detection circuit issues a first level signal based on the detection result when the voltage level of the power supply voltage terminal is lower than a first voltage, and issues a second level signal when the voltage level of the power supply voltage terminal is higher than the first voltage, and the central processing unit issues the enable signal in response to receiving the second level signal. 
     
     
         3 . The USB device according to  claim 2 , wherein the USB function circuit is in an active mode to perform a communication with the host system when an enable signal is received from the central processing unit, and is in a low consumption mode when the enable signal is not received from the central processing unit. 
     
     
         4 . The USB device according to  claim 2 , wherein the battery is in a recharging mode using the power supply from the power supply voltage terminal when detecting the power supplied from the power supply voltage terminal. 
     
     
         5 . A USB device comprising:
 a central processing unit;   an USB function circuit;   a connection detection circuit;   a battery; and   terminals the couple with a host system,   wherein the terminals include two data terminals, a reference voltage terminal, and a power supply voltage terminal,   wherein the battery supplies an operation voltage to the central processing unit,   wherein the connection detection circuit includes an oscillator power supplied from the power supply voltage terminal and a counter, and issues a detection signal to the central processing unit in accordance with count up of the oscillator oscillation by the counter, and   wherein the central processing unit determines whether to issue an enable signal to the USB function circuit in accordance with the detection signal of the connection detection circuit.   
     
     
         6 . The USB device according to  claim 5 , wherein the oscillation of the oscillator is used for the operation clock of the USB function circuit.