| 摘要 |
PURPOSE:To improve the utilizing efficiency of a communication line, by providing a circuit for setting a bus utilizing right in accordance with a priority order decided in advance. CONSTITUTION:A controlling circuit 9 confirms whether a communication line lis used or not, by detecting circuits 2, 4 and 5. In case when the communication line is not used, the controlling circuit 9 sends out a bus using request signal to the communication line l from a sending-out circuit 1. In this case, a built-in timing circuit is started. The time required for making this timing circuit time-up is set to a different value at each device, and a device whose set time is short is made to have a high priority order. In case when a bus utilizing right obtaining signal is not detected within a set time of this timing circuit, its own bus utilizing obtaining signal is sent out from a sending-out circuit 3. In this way, a device of the highest priority can use the bus in accordance with the priority order, and the bus utilizing efficiency can be raised. |
