| 摘要 |
PURPOSE:To process the competition of communication among a plurality of main stations simply, by providing commonly the communication request signal line among a plurality of main stations separately from the data communication lines. CONSTITUTION:A plurality of main stations 21-2n consisting of the data transmission and reception unit 218, request signal transmitter and receiver 219, operational control unit 211 and other are mutually connected with the data line and the communication request line 12 possible for wired OR. On the data line 11, the slave station (not shown) controlled with each main station is connected. Each main station monitors the data flow on the data line 11 and the busy state of the request line 12, and if communication request is present to itselt, request signal is delivered to the request line 12 when the data line 11 and request line 12 are vacant. In this case, the waiting time until each main station checks the carrier detection signal, is differently given every main station to avoid the competition of communication request. |
