Abstract: A ZigBee-compliant radio frequency LSI includes a physical layer portion and a modulator. The physical layer portion has an RF portion, a demodulator, a data transmission and reception control, and a transfer mode determination portion. The transmission and reception control converts, during reception, symbol data received by the demodulator into the byte data received, and outputs, during transmission, the symbol data to be transmitted to the modulator. The determination portion determines, when the first identification data in the received data from the RF portion necessary for determining the received data transfer mode are fixed, the data length of the subsequent second identification data. The determination portion latches, when data corresponding to the determined length of the second identification data are fixed, the data necessary for determining the received data transfer mode to transfer the data to the MAC layer.