| 摘要 |
PURPOSE:To increase the reliability for a process controller containing a multiplexed central arithmetic processing unit, by using the fault signal given from each arithmetic processing unit to an input and extracting a normal output on the basis of the majority logic. CONSTITUTION:The systems 5 and 6 of a doubled central arithmetic processing unit CPU read the control input signal values given from analog input devices 3 and 4 and then produce the output signals by the output of a logic circuit 9 after an arithmetic process. Both CPU-A system 5 and CPU-B system 6 always drive self-diagnosis programs and set the fault signal at ''1'' when a fault arises. The circuit 90 controls input devices 11 and 12 in response to the fault signal and applies the input signal to the normal system. Thus a hardware for switch is eliminated to increase the reliability. |
