US Patent 7555353 Input device of safety unit

This invention provides an input device of safety unit which enables an error diagnosis result referred to in a process of input processing for generating a control data from raw input signal to be referred by a side using the control data also in a safety unit such as a safety master and safety slave. An input device contains a function of outputting status data indicating the error diagnosis result referred to when input signal is converted to control data and the control data obtained by the conversion in pair, so that when the logical value of the control data is “LOW”, whether it originates from that the raw logical value is “LOW” or that “LOW” is compulsorily set due to an error in the terminal can be determined from the logical value of the status data.