One data transmitter for transmitting a broadcast data onto an outside data bus and data receivers, whose number is "n", for individually receiving the transmitted broadcast data are provided. A single error signal line is connected in common to the data transmitter and each of the "n" data receivers. Each of the data receivers notifies an error detection to the data transmitter and the other data receivers via the error signal line with a wired OR connector when its own data receivers detects an error. Being notified of the error detection, the data transmitter re-transmits the data so that all of the data receivers re-receive the data. Accordingly, re-transfer per one data at a broadcast transfer is contemplated.