| 摘要 |
PROBLEM TO BE SOLVED: To control the current consumption in response to the current value that is induced at a transmitting/receiving antenna by detecting the current value that is induced by a received modulated wave and then controlling the cycle of an operating clock according to the detected current value. SOLUTION: A current detection circuit 31, a clock oscillation circuit 32 and a rectifier/voltage control circuit 24 are added to a non-contact card 21. The circuit 31 detects the value of the current that is induced by the modulated wave received via a transmitting/receiving antenna 23. When the detected current value is higher than the prescribed threshold, the circuit 32 shortens the cyclic period of the operating clock which is supplied to a CPU 27 and permits a fast operation since the sufficient power is supplied from the circuit 24. If the detected current value is lower than the prescribed threshold, it means that the power supplied from the circuit 24 is not sufficient. Thus, the cyclic period is lengthened for the operating clock to be supplied to the CPU 27. As a result, the current consumption of the CPU 27 is reduced and the total current consumption is also reduced for the card 21. |
