To protect information stored in RFID tags.

When a main computer emits an RFID command by radio waves through a reader/writer 13, the radio waves are received by an antenna 3A, converted into corresponding electrical signals and are supplied to a clock reproducing circuit 7. The clock reproducing circuit 7 reproduces the signals and supplies them to a demodulator 8. The demodulator 8 demodulates the signals supplied from the clock reproducing circuit 7 and supplies them to a communication logic 10. The communication logic 10 analyzes the signals supplied from the demodulator 8. In the case of an RFID information recording order and when a protection function flag is 1, the stored information is stored in a specified storing region in a nonvolatile memory 11 and is protected against rewriting.

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