| 摘要 |
PURPOSE:To smooth the preparation of a waiting system and to prevent malfunction at switching, by switching an existing system to a waiting system after a device to be controlled is released from both the control systems for a fixed time, if the existing system has a cause to switching. CONSTITUTION:Status information of both control systems is stored in a register 10. Refresh timers A and B are refreshed with a command A or B with a control system A1. The command A is outputted when the system is normal and an I/O bus controlling right is requested, and the command B is outputted when the system is normal and the bus controlling right is given up. If the command A or B is not transmitted because of failure in the control system, a timer outputs a time-up, i.e., a failure signal of the control system. A control section 19 disconnects a bus 18 from buses 16 and 17 if the command A is not transmitted. The objective of this invention can be achieved by outputting the command A of the waiting system after a prescribed time. |
