| 摘要 |
PURPOSE:To improve the reliability of system control and to prevent runaway, by generating a control signal to the head, rear part or branching point of a processing routine of an input/output device only when an output is outputted in a prescribed period or frequency. CONSTITUTION:An output of a digital computer 1 is given to an input device 2 and an operation permitting discrimination circuit 7 and a driving signal 3 is fed to a device 4 to be controlled (e.g., valve switching device). An FF51 of an operation permitting discrimination circuit 7 is inverted at each set/reset of an I/O2, its output is differentiated 52, 53 and inputted to comparators 54, 55 and when the output is a threshold value or over, ''1'' is outputted and when the output is below the threshold value, ''0'' is outputted. While set/reset is executed normally, an AND circuit 57 feeds an output with an output of an OR circuit 56 and an output 8 of the I/02 to output a driving signal 3. If the state change in the set/reset is lost because of some reason, the FF51 feeds no output and the output of the AND circuit 57 is stopped. Thus, the relaiability of the control signal is improved and the system runaway is prevented. |
