Vehicle electronic key

A vehicle electronic key comprising:

• a receiver configured to receive a request signal transmitted from an in-vehicle device mounted on a vehicle, and to output a signal in response to receiving the request signal;
• a transmitter configured to transmit a response signal to the in-vehicle device;
• a key controller configured to determine whether the request signal is received based on the signal output by the receiver, and to control the transmitter to transmit the response signal in response to determining that the request signal is received;
• and
• an acceleration sensor configured to detect an acceleration applied to the vehicle electronic key, to determine whether the detected acceleration is greater than or equal to a predetermined threshold, and to set a vibration detection flag in response to determining the detected acceleration is greater than or equal to the predetermined threshold, the acceleration sensor configured to perform the detecting and determining at every vibration detection cycle, wherein:
• the key controller is further configured to read out the vibration detection flag at every flag read-out cycle, to determine whether the vibration detection flag is set, and to set a response permission state in response to determining the request signal is received and the vibration detection flag is set, and
• the flag read out cycle of the key controller is longer in duration than the vibration detection cycle of the acceleration sensor.