Patent Number: 
Section: claims

1. A control device comprising:an input portion for inputting process signals transmitted from a plant;a numerical processing part that evaluates, by numerical processing performed on a CPU based on a program, a normal or an abnormal state for each inputted process signal, and outputs a respective Boolean value for each inputted process signal, wherein the respective Boolean value is indicative of the normal or abnormal state of the respective inputted process signal;a logical processing part that processes, on a logic circuit, the respective Boolean values, and then outputs a control signal related to a safety protection operation of the plant, wherein the logic circuit includes logic elements realized by hardware logic gates, whereinthe logical processing part comprises:a 1st-OR gate, an AND gate, and a 2nd-OR gate, whereinthe 1st-OR gate receives the respective Boolean values for each inputted process signal and a Boolean value originated in a manual starter of the safety protection operation;the AND gate receives a Boolean value originated in a manual stopper of the safety protection operation and the Boolean value outputted from the 2nd-OR gate, and then outputs the control signal related to a safety protection operation of the plant; andthe 2nd-OR gate receives a Boolean value outputted from the 1st- OR gate and the control signal outputted from the AND gate, and then outputs a Boolean value to the AND gate. 2. The control device according to claim 1, wherein the numerical processing part performs the numerical processing sequentially for the inputted process signals, and then finally outputs an operation complete signal. 3. The control device according to claim 1, further comprising:a watch dog timer for reporting a timeout information a period to end from a start of the logical processing part or a period to end of the logical processing part from a start of the numerical processing part exceeds a setting time. 4. The control device according to claim 1, wherein the numerical processing part calculates a hash value of the program and a constant, and then outputs the hash value with the respective Boolean values;the logical processing part evaluates the identity of a new hash value inputted at a first time and a last hash value inputted at a time prior to the first time. 5. The control device according to claim 1, wherein the inputted process signals are multiplexed with a cyclic code; and further comprising:a receiver for receiving the multiplexed process signals and then checking an error from the cyclic code; and a timer for holding the checked inputted process signals in the input portion for a predetermined time interval. 6. The control device according to claim 1, whereinthe input portion, the numerical processing part, and the logical processing part are mounted in separate extended boards respectively;each extended board is connected with a bus via a connector.