Programmable logic controller

A programmable logic controller comprising:

• a CPU module;
• and an input module that generates internal data corresponding to an externally input signal input and transmits the internal data to the CPU module via communication, wherein
• the input module comprises a first control unit that generates and outputs first control data when the input signal is input, and a second control unit that generates and outputs second control data when the input signal is input,
• the second control unit generates the second control data by encoding second input data, which is input data corresponding to the input signal, into data that cannot be decoded by the first control unit, and transmits the second control data to the first control unit,
• the first control unit output the first control data including first input data, which is input data corresponding to the input signal, and the second control data, and
• the input module generates the internal data based on the first control data and transmit the internal data to the CPU module,
• the CPU module has a function of decoding the second control data, and extracts the first input data and the second input data from the internal data to determine whether the input data is correct by performing match comparison between the first input data and the second input data.