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

A system program for a PLC in a CPU unit of the PLC, the system program being stored in a memory means and being executed by a microprocessor, wherein

• the CPU unit comprises:
• the microprocessor;
• the memory means having a main memory of the microprocessor;
• a first communication circuit transmitting first output data and receiving first input data with a PLC system bus;
• and
• a second communication circuit transmitting second output data and receiving second input data with a field network,
• the CPU unit controls a control target by repeating transmission of the first output data and the second output data, reception of the first input data and the second input data, and execution of a control program stored in the memory means and using the first input data and the second input data to generate the first output data and the second output data,
• the system program includes, as an execution preparation command of a control operation, a command generating, in the main memory, a calculation buffer in which, accompanying execution of the control program, the first input data and the second input data are read and the first output data and the second output data are written;
• a first transfer buffer storing the first output data transmitted by the PLC system bus and the first input data received by the PLC system bus;
• and a second transfer buffer storing the second output data transmitted by the field network and the second input data received by the field network, and
• the system program comprises, as an execution control command of the control operation:
• a control program initiation command initiating execution of the control program;
• a first output copy command for copying the first output data from the calculation buffer to the first transfer buffer;
• a second output copy command for copying the second output data from the calculation buffer to the second transfer buffer;
• a first input copy command for copying the first input data from the first transfer buffer to the calculation buffer;
• a second input copy command for copying the second input data from the second transfer buffer to the calculation buffer;
• and
• an input/output control command comprising at least one of:
• a first input/output control command for controlling the first communication circuit;
• and
• a second input/output control command for controlling the second communication circuit,
• the input/output control command being configured such that a first input/output process and a second input/output process are executed in parallel, wherein
• the first input/output process includes a process outputting the first output data from the first transfer buffer, through the first communication circuit, to a first instrument in the PLC system bus, and a process inputting the first input data from the first instrument, through the first communication circuit, to the first transfer buffer, and
• the second input/output process includes a process outputting the second output data from the second transfer buffer, through the second communication circuit, to a second instrument in the field network, and a process inputting the second input data from the second instrument, through the second communication circuit, to the second transfer buffer.

A recording medium storing a system program for a PLC in a CPU unit of the PLC, the system program being stored in a memory means and being executed by a microprocessor, wherein

• the CPU unit comprises:
• the microprocessor;
• the memory means having a main memory of the microprocessor;
• a first communication circuit transmitting first output data and receiving first input data with a PLC system bus;
• and
• a second communication circuit transmitting second output data and receiving second input data with a field network,
• the CPU unit controls a control target by repeating transmission of the first output data and the second output data, reception of the first input data and the second input data, and execution of a control program stored in the memory means and using the first input data and the second input data to generate the first output data and the second output data,
• the system program includes, as an execution preparation command of a control operation, a command generating, in the main memory, a calculation buffer in which, accompanying execution of the control program, the first input data and the second input data are read and the first output data and the second output data are written;
• a first transfer buffer storing the first output data transmitted by the PLC system bus and the first input data received by the PLC system bus;
• and a second transfer buffer storing the second output data transmitted by the field network and the second input data received by the field network, and
• the system program comprises, as an execution control command of the control operation:
• a control program initiation command initiating execution of the control program;
• a first output copy command for copying the first output data from the calculation buffer to the first transfer buffer;
• a second output copy command for copying the second output data from the calculation buffer to the second transfer buffer;
• a first input copy command for copying the first input data from the first transfer buffer to the calculation buffer;
• a second input copy command for copying the second input data from the second transfer buffer to the calculation buffer;
• and
• an input/output control command comprising at least one of:
• a first input/output control command for controlling the first communication circuit;
• and
• a second input/output control command for controlling the second communication circuit,
• the input/output control command being configured such that a first input/output process and a second input/output process are executed in parallel, wherein
• the first input/output process includes a process outputting the first output data from the first transfer buffer, through the first communication circuit, to a first instrument in the PLC system bus, and a process inputting the first input data from the first instrument, through the first communication circuit, to the first transfer buffer, and
• the second input/output process includes a process outputting the second output data from the second transfer buffer, through the second communication circuit, to a second instrument in the field network, and a process inputting the second input data from the second instrument, through the second communication circuit, to the second transfer buffer.