| 摘要 |
PURPOSE:To decrease the number of signal lines for a bus by applying the control of permission and inhibition of data input/output by means of a bus request flag signal sent from the active controller to a clock line in the bus so as to eliminate the need for the act control line. CONSTITUTION:When a controller 1 goes to, for example an act state, the controller 1 sends a bus request flag signal from the controller 1 to the clock line 33 in the bus 3, and a bus request flag detection means 53 detecting the bus request flag signal in each input/output device 5 sends a control signal to connect the device control means 51 to the bus 3 to the input/output gate means 50 to instruct the data input/output permission to the controller 1. Simultaneously, a bus request flag detection means 53 sends a control signal to the bus request flag detection means 54 to give the instruction data input/output inhibition to the controller 2 in the standby state. Thus, no control line for the act control is required at every duplexed bus.
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