CPU unit of PLC, system program for PLC, and recording medium storing system program for PLC

A method for controlling motor movement of a machine, the motor movement to be executed with a programmable logic controller (PLC), the method comprising:

• storing a first control program and a second control program in a storage;
• transmitting output data and receiving input data over a communications circuit in a control cycle period;
• generating a first execution control instruction causing a microprocessor to begin execution of the first control program at every first execution cycle of the same period as the control cycle period, the first control program producing a first motion command value data for controlling motor movement;
• generating a second execution control instruction causing the microprocessor to begin execution of the second control program at every second execution cycle whose period is an integral multiple of at least twice the control cycle period, the second control program producing a second motion command value data for controlling motor movement;
• wherein the second control instruction includes an instruction causing the microprocessor to begin, in a control cycle in which the second execution begins, execution of the second control program after an end of execution of the first control program, and
• wherein if the second control program is not completed before the end of the control cycle, to begin execution of an unexecuted portion of the second control program after the end of execution of the first control program in the next control cycle.

A non-transitory computer readable medium storing a program that allows a computer apparatus to perform a process for controlling motor movement of a machine, the program allowing the computer apparatus to perform:

• storing a first control program and a second control program in a storage;
• transmitting output data and receiving input data over a communications circuit in a control cycle period;
• generating a first execution control instruction causing a microprocessor to begin execution of the first control program at every first execution cycle of the same period as the control cycle period, the first control program producing a first motion command value data for controlling motor movement;
• generating a second execution control instruction causing the microprocessor to begin execution of the second control program at every second execution cycle whose period is an integral multiple of at least twice the control cycle period, the second control program producing a second motion command value data for controlling motor movement;
• wherein the second control instruction includes an instruction causing the microprocessor to begin, in a control cycle in which the second execution begins, execution of the second control program after an end of execution of the first control program, and
• wherein if the second control program is not completed before the end of the control cycle, to begin execution of an unexecuted portion of the second control program after the end of execution of the first control program in the next control cycle.