DATA COMPARISON SYNCHRONIZING SYSTEM SERIAL COMMUNICATION SYSTEM

PURPOSE:To confirm a fault of a communication line or receiving operation at a receiver side by sending back a received data to a reception line not required at the sender side via a transmission line not required at the receiver side synchronously with a clock signal, and allowing the sender side to compare the transmission data and the reception data. CONSTITUTION:Shift registers 1, 1' send a parallel data 2 from a transmission line 6 at the time of transmitting and receives a serial data from a reception line 11 at the time of receiving, and outputs the data as a parallel data 12. The sender side transmission line 6 and the receiver side reception line 11, the receiver side transmission line 10 and the sender side reception line 7, and a sender side clock line 8 and a receiver side clock line 9 are coupled by a communication line 13. Then the transmission data is inputted to a comparator 5, and simultaneously inputted to the other input of the comparator via the sender side transmission line 6, the receiver side reception line 11, the receiver side transmission line 10 and the sender side reception line 7 and outputted as a comparison output 3. Thus, the communication data is checked at the same time of transmission.