Safety control unit, safety control method, and safety control program

A safety control method, comprising:

• storing, in a memory, a system program for safety control, a control program for safety control comprising a sequence command computation program and a user program, and control data;
• executing safety control using the control data, the system program, the sequence command computation program, and the user program;
• executing a data refresh program, included in the system program, for executing a data refresh for safety control comprising:
• refreshing safety input data in the control data stored in the memory;
• and outputting safety computation results;
• receiving a change of the sequence command computation program or a change of the user program;
• determining whether a safety control continuation setting is set;
• and
• in response to determining that the safety control continuation setting is set:
• stopping execution of the sequence command computation program and the user program in response to receiving the change of the sequence command computation program or the user program while continuing to execute the data refresh program;
• unloading the sequence command computation program and the user program from the memory;
• loading, to the memory, the sequence command computation program and the user program including the change of the sequence command computation program or the user program while continuing to execute the data refresh program;
• and
• resuming execution of the sequence command computation program and the user program including the change of the sequence command computation program and the user program while continuing to execute the data refresh program.

A non-transitory computer-readable storage medium storing a safety control program, which when read and executed causes a computation control part to execute operations comprising:

• storing, in a memory, a system program for safety control, a control program for safety control comprising a sequence command computation program and a user program, and control data;
• executing safety control using the control data, the system program, the sequence command computation program, and the user program;
• executing a data refresh program, included in the system program, for executing a data refresh for safety control comprising:
• refreshing safety input data in the control data stored in the memory;
• and outputting safety computation results;
• receiving a change of the sequence command computation program or a change of the user program;
• determining whether a safety control continuation setting is set;
• and
• in response to determining that the safety control continuation setting is set:
• stopping execution of the sequence command computation program and the user program in response to receiving the change of the sequence command computation program or the user program while continuing to execute the data refresh program;
• unloading the sequence command computation program and the user program from the memory;
• loading, to the memory, the sequence command computation program and the user program including the change of the sequence command computation program or the user program while continuing to execute the data refresh program;
• and
• resuming execution of the sequence command computation program and the user program including the change of the sequence command computation program and the user program while continuing to execute the data refresh program.