PLC system, and method for controlling input/output refresh period thereof

A method of controlling an input/output refresh period of a PLC system, the method comprising:

• storing an integrated operation program in a memory, wherein the integrated operation program is compiled such that an input/output refresh execution command is added thereto using a program supporter;
• and
• sequentially computing, by a central processing unit, a plurality of control programs included in the integrated operation program to control operations of a plurality of extension modules,
• wherein sequentially computing, by the central processing unit, the plurality of control programs includes:
• when computing of at least one control program among the plurality of control programs has been completed, outputting result data of execution of at least one control program on which the computing has been completed based on the added input/output refresh execution command,
• when at least one control program among the plurality of control programs is completed, checking whether the input/output refresh execution command is set,
• when the input/output refresh execution command is set, comparing data on an operation state information of each extension modules input from an input port with the result data of execution of the at least one control program,
• when the data on the operation state information of the each extension modules and the result data of execution of the at least one control program are different, performing an input/output refresh, and
• when the data on the operation state information of the each extension modules and the result data of execution of the at least one control program are the same, executing a next control program without executing the input/output refresh.