| 摘要 |
PURPOSE:To improve the transmission efficiency with a simple circuit by setting an address distinguishing cipher data and non-cipher data to an address section of a frame format of a high level data link control means and transmitting and receiving data through the same communication line. CONSTITUTION:A cipher processing section 20 ciphers data, and a data processing section transfers it to a transmission buffer 32 and requests transmission to control section 35. A communication control LSI30 composes frames of cipher data and transmits the result via a transmission shift register 33, an OR circuit 50, and an MODEM60. The data processing section 10 adds a non-ciphered address to the frame of the non-cipher data via a communication LSI40 and transmits the result via the OR circuit 50 and the MODEM60. In receiving data, it is inputted to reception shift registers 34, 44 from the MODEM, comparator sections 37, 47 detect whether the address of the frame indicates a ciphered message or not, and the ciphered message is subjected to data processing 10 via the LSI30 and the non-ciphered message is subjected to data processing 10 via the LSI40. Thus, mixed messages of the ciphered and the non-ciphered message are transmitted efficiently with a simple circuit. |
