Patent ID: 7000835

Claim:
A noncontact type IC card for use in an IC card system that includes an external device having a sending section which sends a power wave for operations to the IC card, and a transmitting section which transmits a write command to the IC card receiving the power wave for operations sent from the sending section, the IC card performing writing of data in response to a request from the external device and comprising: a voltage detecting section configured to detect a voltage level of an operating voltage generated from the power wave received from the external device; a first checking section configured to detect, by the voltage detecting section, the voltage level of the operating voltage and checks whether or not the detected voltage level of the operating voltage is a predetermined voltage level, when the writing of the data to the memory is started in response to the write command received from the external device; a write executing section configured to execute the writing of the data to the memory if the first checking section determines that the detected voltage level of the operating voltage is the predetermined voltage level; a second checking section configured to detect the voltage level of the operating voltage obtained after the writing of the data to the memory is terminated, by the voltage detecting section, and which checks whether or not the detected voltage level is a predetermined voltage level; a control section which executes again processing of the first checking section, the write executing section, and the second checking section after waiting for a predetermined period of time, if the first checking section determines that the voltage level of the operating voltage is not the predetermined voltage level or if the second checking section determines that the voltage level of the operating voltage is not the predetermined voltage level; and a setting section configured to set the predetermined period of time in which the control section waits, in accordance with data prestored in the memory when the IC card starts by receiving the power wave for operations sent from the sending section of the external device.