Network data server for use with programmable logic controllers and programmable logic controller system formed using such network data servers

A network data server apparatus connected to a plurality of programmable logic controller units (PLCs) and at least one FA controller unit in a manner enabling bidirectional communications, the network data server apparatus comprising:

• a PLC memory for storing data for each of said plurality of programmable logic controller units at respective memory addresses;
• a receiving means for receiving data transmitted from any one of said plurality of programmable logic controller units or from said FA controller unit;
• a write means for writing into said PLC memory data received by said receiving means;
• a read means for reading data stored in said PLC memory;
• a transmitting means for transmitting the data read out by said read means to any of said plurality of programmable logic controller units or to said FA controller unit;
• a copy data list section which contains a correspondence of memory addresses from which data is copied and memory addresses to which data is written for data copying;
• and
• a control means for causing said read means to read out from said PLC memory, as copy data, data stored at said memory addresses from which data is copied, according to the correspondence contained in said copy data list section, and causing said write means to write the copy data into said PLC memory at said memory addresses to which data is copied, according to the correspondence contained in said copy data list section.

A programmable logic controller system including:

• a plurality of network data server units, each of said network data server units being connected to a respective plurality of programmable logic controllers in a manner enabling bidirectional communications, and each of said network data server units being connected to a respective data server control unit in a manner enabling bidirectional communications, wherein each respective data server control unit is connected to at least one FA controller in a manner enabling bidirectional communications;
• each of said plurality of network data server units comprises:
• a PLC memory for storing data for the respective plurality of programmable logic controllers at specified memory addresses,
• a receiving means for receiving data transmitted from one of said plurality programmable logic controllers or from said respective data server control unit,
• a write means for writing data received by said receiving means into said PLC memory,
• a read means for reading data stored in said PLC memory,
• a transmitting means for transmitting the data read out by said read means to one of said plurality of programmable logic controllers or to said data server control unit,
• a transmitting and receiving means for bidirectional communications between said plurality of network data server units,
• a copy data list section containing a correspondence of memory addresses from which data is copied, and memory addresses to which data is copied, and
• a control means for executing communications with said respective data server control unit inquiring a destination for data storage each time data is received from one of said plurality of programmable logic controllers, deciding whether the received data is to be written in the PLC memory or is to be transmitted to another network data server apparatus according to a reply from said data server control unit, reading out copy data stored in said PLC memory at said memory addresses from which data is copied with said read means according to the correspondence contained in said copy data list section, and writing the copy data to said PLC memory at said memory addresses to which data is copied with said write means according to the correspondence contained in said copy data list section;
• wherein each of said respective data server control units comprises:
• a storage medium data memory for storing therein storage medium data such as a type, storage capacity, and operating speed of each memory medium constituting said PLC memory in each one of said plurality of network data server units,
• a PLC data storage data memory for storing therein PLC data storage data indicating which data is stored in said PLC memory of the respective one of said plurality network data server units,
• a means for writing the PLC data storage data into said PLC data storage data memory,
• a means for reading the PLC data storage data written in said PLC data storage data memory, and
• a control means for providing controls to distribute and allocate data among the plurality of network data server units, to write the PLC data storage data into said PLC storage data memory according to the distributed allocation of data with said write means to read out corresponding PLC data storage data from said PLC data storage data memory each time a communication inquiring destination for storing data is received from said network data server apparatus or said FA controller is executed, decide the destination for storage of the data, and transmit the data concerning the destination for data storage to a station having issued the inquiry;
• wherein each of said plurality of network data server units stores data in the respective PLC memory according to the memory medium data written in said memory medium data memory and.