Programmable logic controller

A programmable logic controller comprising:

• an input module that receives an input signal that is inputted externally and that comprises first and second control units that process, respectively, first and second input data both obtained from the input signal, the first and second input data being presented at signal levels that can be processed in the first and second control units, respectively;
• and
• a CPU module configured to communicate with the input module via a communication line, wherein:
• the second control unit generates second control data by encoding the second input data into the second control data and transmits the generated second control data to the first control unit, the first control unit being unable to decode the second control data;
• the first control unit generates first control data by integrating the first input data with the second control data;
• the input module generates internal data based on the generated first control data and transmits the internal data to the CPU module via the communication line;
• and
• the CPU module divides the received internal data into the first input data and the second control data, acquires the second input data by decoding the second control data, and thereby extracts the first input data and the second input data from the internal data to determine whether the first input data and the second input data are correct by performing match comparison between the first input data and the second input data extracted from the internal data.