| 摘要 |
<p>An IC card (10) has data a transmission/receiving circuit (4, 5, 6) for conducting exchange of data with an external device, a data processing circuit (1, 2, 3) connected to said data transmission/receiving circuit for processing the data, a battery (8) for supplying said data transmission/receiving circuit and said data processing circuit with electrical power. A charge device (12) such as a capacitor is provided and is charged at a predetermined time constant by the power from said battery (8). A charging control circuit (11) controls the state of connection between said battery and said charge device in accordance with a control signal from said data processing circuit. A comparator circuit (14) compares the output voltage from said charge device (12) with a reference value, and a time measuring counter (16) measures the time from a moment at which an electrical connection between said battery (8) and said charge device (12) is completed by said charging control circuit (11) to a moment at which said comparator circuit (14) detects the output voltage from said charge circuit exceeding said reference value. It is possible to measure the time a plurality of times to determine a mean value to eliminate any fluctuation in the measured results. The rate of reduction in the voltage battery may be detected to inform any drastic drop of the battery voltage which occurs when the battery life is going to expire. <IMAGE></p> |
