A remote terminal device having an industrial structure and comprising: a main module that receives control logic information of a field device from an input/output module; and a programmable logic controller function module that receives the control logic information from the main module, performs a logic corresponding to the control logic information, and outputs a result of the performed logic, wherein the PLC function module includes a dual port RAM including a plurality of memory areas, and a PLC chip that reads the control logic information written on one of the plurality of memory areas, performs the logic corresponding to the read control logic information, and outputs the result of the performed logic to another one of the plurality of memory areas, wherein the memory areas of the dual port RAM include an input variable area on which a value of an input variable is read or written, and an output variable area on which a value of an output variable is read or written, wherein the PLC chip stores a plurality of values of input variables which correspond to a plurality of logic values, respectively, reads the value of the input variable on the input variable area, searches for a logic value corresponding to the read value of the input variable and performs the logic corresponding to the searched for logic value, writes a result of the performed logic on the output variable area of the dual port RAM, and wherein the main module reads the value of the output variable on the output variable area of the dual port RAM, characterized in that the main module transmits, to the input/output module, control information corresponding to the read value of the output variable, the input/output module transmits the control information to the field device, and an operation of the field device is controlled according to the control information. a main module that receives control logic information of a field device from an input/output module; and a programmable logic controller function module that receives the control logic information from the main module, performs a logic corresponding to the control logic information, and outputs a result of the performed logic, wherein the PLC function module includes a dual port RAM including a plurality of memory areas, and a PLC chip that reads the control logic information written on one of the plurality of memory areas, performs the logic corresponding to the read control logic information, and outputs the result of the performed logic to another one of the plurality of memory areas, wherein the memory areas of the dual port RAM include an input variable area on which a value of an input variable is read or written, and an output variable area on which a value of an output variable is read or written, wherein the PLC chip stores a plurality of values of input variables which correspond to a plurality of logic values, respectively, reads the value of the input variable on the input variable area, searches for a logic value corresponding to the read value of the input variable and performs the logic corresponding to the searched for logic value, writes a result of the performed logic on the output variable area of the dual port RAM, and stores a plurality of values of input variables which correspond to a plurality of logic values, respectively, reads the value of the input variable on the input variable area, searches for a logic value corresponding to the read value of the input variable and performs the logic corresponding to the searched for logic value, writes a result of the performed logic on the output variable area of the dual port RAM, and wherein the main module reads the value of the output variable on the output variable area of the dual port RAM, the main module transmits, to the input/output module, control information corresponding to the read value of the output variable, the input/output module transmits the control information to the field device, and an operation of the field device is controlled according to the control information.