Wireless integrated circuit

A radio LSI is provided that is not to cause a delay in sending acknowledgement data. A latch circuit provided in a sending/receiving section latches frame control information out of data being received. A decoder decodes the frame control information to decode a data length and structure of an address field. Furthermore, a latch circuit latches the address-field data of the reception data according to the decoded address-field information. A comparing circuit compares a content of a register entered with an address of the opposite-of-communication completely prepared data to be sent, with a source address of the data being received, to determine a setting/resetting of frame pending in acknowledgement data. A content of the determination is sent to a data-link section. This provides information required for acknowledgement data before completely receiving data, thus eliminating the possibility to cause a delay in sending acknowledgement data.