Semiconductor device for passive RFID, IC tag, and control method thereof

A semiconductor device for a tag included in a communication system, the communication system including the tag and a reader/writer communicating by a radio signal with the tag, the communication system executing a verify process that the reader/writer reads from the tag a write data to determine whether a write operation is correct or not after the reader/writer writes in the tag the write data, the semiconductor device comprising:

• a supply voltage generator responsive to the radio signal to generate supply voltage therefrom;
• a control unit being operable on the supply voltage of a predetermined voltage value or more, executing a command included in the radio signal;
• a memory coupled to the control unit and responsive to a memory control signal therefrom, to receive or supply data to be stored or stored therein;
• a booster coupled to the supply voltage generator, boosting the supply voltage to generate a boost voltage during a write cycle;
• and
• a detector detecting whether the boost voltage generated by the booster is smaller than a minimum write voltage required for writing to the memory,
• wherein the control unit does not execute a transmission corresponding to a read operation in the verify process in response to the boost voltage being smaller than the write voltage.

A communication method for a communication system including:

• a reader/writer and a tag, the tag comprising a supply voltage generator responsive to a radio signal from the reader/writer to generate supply voltage therefrom;
• a control unit being operable on the supply voltage of a first voltage value or more, executing a command including in the radio signal;
• a memory responsive to a control signal from the control unit, to receive or supply data to be stored or stored therein;
• and
• a booster boosting the supply voltage more than a second voltage value that is larger than the first voltage value, to generate a write voltage required for writing to the memory during write cycle, the booster boosting the supply voltage less than the second voltage value to generate a write voltage and being insufficient for writing to the memory during the write cycle,
• the communication method comprising:
• outputting the radio signal from the reader/writer to the tag;
• generating the supply voltage from a received radio signal in the supply voltage generator;
• detecting whether a generated supply voltage is smaller than the second voltage value;
• transmitting from the reader/writer to the tag via the radio signal a write command to make a write process for a predetermined address of the memory execute after the detecting;
• transmitting from the reader/writer to the tag via the radio signal a read command to make a read process for the predetermined address of the memory execute after the transmitting the write command;
• and
• processing the read command in the control unit,
• wherein the control unit does not execute a transmission process corresponding to the read command in response to the supply voltage being smaller than the second voltage in the processing.