| 摘要 |
PURPOSE:To attain transmission of control data without using a memory for duplication nor a high-order bus by reading out the control data written to the memory for duplication by a back-up controller in a fault mode of a main controller to continue the control. CONSTITUTION:A main controller 10 has a fault by some reason and this fault is detected by a CPU21 of a back-up controller 20 through a duplication diagnosis line LG. Thus the controller 20 backs up the controller 10, and the controller 20 can give access to a PIO bus B1. Then the controller 20 produces a read control signal and reads out the control data written into a RAM40 for duplication to perform the arithmetic processing and to continue the process control. In this case, the control data in a control process especially the set value of the control parameter is sometimes changed during control. Even under such conditions, the process control can be continued with no disturbance since the set value of the control parameter is stored in a RAM40. |
