A control system, comprising: a first control unit adapted to execute a first control program; a second control unit adapted to execute a second control program; and an input and output unit (10, 250) adapted to serve to input a signal from a field and/or output a signal to the field, wherein the control system is characterized in that the first control unit includes: a data transfer relay unit (20, 120) adapted to execute a process of transferring input data corresponding to a signal input to the input and output unit to the second control unit according to a request from the second control unit, and/or a process of transferring output data that defines a signal to be output from an input and output unit from the second control unit to the input and output unit, a storage unit adapted to store the data transferred by the data transfer relay unit, and a monitoring processing unit adapted to determine whether or not a predetermined trigger condition has been satisfied on the basis of the data held in the storage unit, and outputs a value of any data held in the storage unit according to a predetermined output configuration when it is determined that the trigger condition has been satisfied, wherein the first control unit is a standard control unit adapted to control a control target according to the first control program and the first control program is a standard control program, the second control unit is a safety control unit and the second control program is a safety program, and the input and output unit includes a safety input and output unit adapted to serve to input a signal from a safety component and/or output a signal to the safety component. a first control unit adapted to execute a first control program; a second control unit adapted to execute a second control program; and an input and output unit (10, 250) adapted to serve to input a signal from a field and/or output a signal to the field, wherein the control system is characterized in that the first control unit includes: a data transfer relay unit (20, 120) adapted to execute a process of transferring input data corresponding to a signal input to the input and output unit to the second control unit according to a request from the second control unit, and/or a process of transferring output data that defines a signal to be output from an input and output unit from the second control unit to the input and output unit, a storage unit adapted to store the data transferred by the data transfer relay unit, and a monitoring processing unit adapted to determine whether or not a predetermined trigger condition has been satisfied on the basis of the data held in the storage unit, and outputs a value of any data held in the storage unit according to a predetermined output configuration when it is determined that the trigger condition has been satisfied, wherein the first control unit is a standard control unit adapted to control a control target according to the first control program and the first control program is a standard control program, the second control unit is a safety control unit and the second control program is a safety program, and the input and output unit includes a safety input and output unit adapted to serve to input a signal from a safety component and/or output a signal to the safety component. a data transfer relay unit (20, 120) adapted to execute a process of transferring input data corresponding to a signal input to the input and output unit to the second control unit according to a request from the second control unit, and/or a process of transferring output data that defines a signal to be output from an input and output unit from the second control unit to the input and output unit, a storage unit adapted to store the data transferred by the data transfer relay unit, and a monitoring processing unit adapted to determine whether or not a predetermined trigger condition has been satisfied on the basis of the data held in the storage unit, and outputs a value of any data held in the storage unit according to a predetermined output configuration when it is determined that the trigger condition has been satisfied, wherein the first control unit is a standard control unit adapted to control a control target according to the first control program and the first control program is a standard control program, the second control unit is a safety control unit and the second control program is a safety program, and the input and output unit includes a safety input and output unit adapted to serve to input a signal from a safety component and/or output a signal to the safety component.