Cpu of plc, system program for plc, and recording medium storing system program for plc

A PLC system program executed in a CPU unit of a PLC having a motion control function to control motion of a motor,

• the CPU unit of the PLC comprising:
• a memory storing a first user program;
• a microprocessor;
• and
• a communication circuit,
• the CPU unit of the PLC being configured to be capable of repeatedly performing output processing of motion instruction value data and input processing of input data for motion control and executing a motion calculation program for every motion control cycle having a constant period,
• the CPU unit of the PLC being configured to be capable of repeatedly executing the first user program for every first user program execution cycle having a period of integral multiple of the period of the motion control cycle, the first user program being created according to a purpose of control by a user and comprising processing of providing an instruction required for execution of the motion calculation program,
• the PLC system program comprising:
• the motion calculation program;
• and
• a scheduler program controlling execution of the first user program and the motion calculation program,
• the communication circuit transmitting the motion instruction value data as at least a portion of the output processing and receiving the input data for motion control as at least a portion of the input processing in each motion control cycle,
• the scheduler program comprising:
• a command to cause the microprocessor to start execution of the motion calculation program in each motion control cycle;
• a command to cause the microprocessor to start execution of the first user program in each first user program execution control cycle;
• and
• a command to repeat the output processing and the input processing, start of execution of the first user program, end of execution of the first user program, and start of execution of the motion calculation program in this sequence for every period corresponding to the period of the first user program execution cycle, wherein
• when the first user program comprises processing of calculating user program output data by using the input data for motion control, and the user program output data is used by the motion calculation program, a time required from start of the input processing to end of the output processing of the motion instruction value data reflecting the input data for motion control input in the input processing corresponds to the period of the first user program execution cycle.

A recording medium storing a PLC system program executed in a CPU unit of a PLC having a motion control function to control motion of a motor,

• the CPU unit of the PLC comprising:
• a memory storing a first user program;
• a microprocessor;
• and
• a communication circuit,
• the CPU unit of the PLC being configured to be capable of repeatedly performing output processing of motion instruction value data and input processing of input data for motion control and executing a motion calculation program for every motion control cycle having a constant period,
• the CPU unit of the PLC being configured to be capable of repeatedly executing the first user program for every first user program execution cycle having a period of integral multiple of the period of the motion control cycle, the first user program being created according to a purpose of control by a user and comprising processing of providing an instruction required for execution of the motion calculation program,
• the PLC system program comprising:
• the motion calculation program;
• and
• a scheduler program controlling execution of the first user program and the motion calculation program,
• the communication circuit transmitting the motion instruction value data as at least a portion of the output processing and receiving the input data for motion control as at least a portion of the input processing in each motion control cycle,
• the scheduler program comprising:
• a command to cause the microprocessor to start execution of the motion calculation program in each motion control cycle;
• a command to cause the microprocessor to start execution of the first user program in each first user program execution control cycle;
• and
• a command to repeat the output processing and the input processing, start of execution of the first user program, end of execution of the first user program, and start of execution of the motion calculation program in this sequence for every period corresponding to the period of the first user program execution cycle, wherein
• when the first user program comprises processing of calculating user program output data by using the input data for motion control and the user program output data is used by the motion calculation program, a time required from start of the input processing to end of the output processing of the motion instruction value data reflecting the input data for motion control input in the input processing corresponds to the period of the first user program execution cycle.