Patent ID: 7738839

Claim:
A semiconductor device comprising: an antenna for transmitting and receiving a communication signal; a receiving circuit for discriminating the communication signal; a state control register having bit fields for a reception processing state flag, an arithmetic processing state flag, and a transmission processing state flag, an arithmetic circuit for performing a decoding and encoding process for encoded receiving and transmitting data, the arithmetic circuit configured to operate based on the reception processing state flag, the arithmetic processing state flag, and the transmission processing state flag; and a transmitting circuit for transmitting an arithmetic result of the arithmetic circuit; wherein the receiving circuit operates while stopping operation of the arithmetic circuit and the transmitting circuit when an operating magnetic field varies; wherein the arithmetic circuit operates while stopping operation of the receiving circuit and the transmitting circuit when the operating magnetic field does not vary; wherein the transmitting circuit operates while stopping operation of the receiving circuit and the arithmetic circuit when the operating magnetic field varies; wherein a state of the state control register changes into an arithmetic processing state after a reception process is completed; wherein a state of the state control register changes into a transmission processing state after an arithmetic process is completed; and wherein a state of the state control register changes into a reception processing state when transmission is completed.