Safety input device

A safety input device of a control device, the safety input device being configured to send an input signal from an input terminal portion to an arithmetic device of the control device as input data and to execute a self-diagnosis of the safety input device, the safety input device comprising:

• an input controller configured to control conversion of the input signal into the input data and transmission of the input data to the arithmetic device synchronously with a control cycle set up by the arithmetic device;
• an output controller configured to make an instruction to output preset first self-diagnosis pattern data synchronously with the control cycle set by the arithmetic device;
• a test pattern generating unit configured to encode the first self-diagnosis pattern data sent from the output controller into a pulse train signal having a pulse width equal to or smaller than a predetermined pulse width and to output the pulse train signal in accordance with a baseband transmission system;
• a combination input unit configured to combine the pulse train signal with the input signal from the input terminal portion;
• an input interface unit configured to convert the input signal into a signal having an operating signal level of the safety input device and to send the signal to the input controller and the combination input unit at a timing instructed by the input controller;
• a pattern reconfiguration unit configured to reconfigure an output signal from the combination input unit as second self-diagnosis pattern data by decoding the output signal;
• and
• a comparator configured to compare the first self-diagnosis pattern data with the second self-diagnosis pattern data to judge the presence or absence of a difference between the first self-diagnosis pattern data and the second self-diagnosis pattern data, wherein
• the presence or absence of a failure is judged based on the difference between the first self-diagnosis pattern data and the second self-diagnosis pattern data compared to each other, whereby the processing of the input data and the self-diagnosis are performed in parallel.