| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of efficiently inspecting an input/output circuit in a short time by providing a circuit capable of inspecting the input/output circuit in a signal input/output part so as to allow a system itself to self- diagnose the input/output circuit. SOLUTION: A signal input/output device in a control system provided with CPU 1 and the signal input/output device consisting of an input buffer 2, an input insulation circuit 3, an output buffer 4 and an output insulation circuit 5 is provided with a first switch 11 applying voltage for diagnosis to the power source side terminal 6 of signal input terminals, and a second switch 12 connecting the earth side terminal 7 of the signal input terminals and the power source side terminal 8 of signal output terminals. Then after the first and second switches 11 and 12 are closed in a state where an external device is separated from the signal input/output terminals, an output signal is outputted from CPU 1 to the output insulation circuit 5 through the output buffer 4, an input signal is read into CPU 1 through the input insulation circuit 3 and the input buffer 2, and CPU 1 compares the output signal with the input signal to diagnose the signal input/output device. |
