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About the File Management Functions

The following functions enable sequential read / write operations in disk files:

Each file is identified in the application by a unique handle manipulated as a DINT value. The file handles are allocated by the target system. Handles are returned by the Open functions and used in all other calls for identifying the file.

Related function blocks:

LogFileCSV  log values of variables to a CSV file

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• • These functions can have a serious impact on CPU load and the life expectancy of a flash drive. It is highly recommended that these be used on an event basis, and not at every PLC"Programmable Logic Controller" A Programmable Logic Controller, PLC, or Programmable Controller is a digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines. Used to synchronize the flow of inputs from (physical) sensors and events with the flow of outputs to actuators and events cycle.
    
  • Files are opened and closed directly by the Operating System of the target. Opening some files can be dangerous for system safety and integrity. The number of open files (from F_AOPEN, F_ROPEN, and F_WOPEN) is limited by the resources available on the target system.
  • Ensure that each file successfully opened using F_AOPEN, F_ROPEN, and F_WOPEN has a corresponding F_CLOSE to close the file. Closing the file will release the file ID, making it available for operations on other files.

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• • Opening a file with F_AOPEN, F_ROPEN, and F_WOPEN can be unsuccessful (invalid path or file name, too many open files...) Your application must check the file ID for a NULL value. If the file ID is NULL (zero), then file read or write operations will fail..
    
  • File management may be unavailable on some targets.
    
  • Memory on the SD card is available in addition to the existing flash memory.
    
  • Valid paths for storing files depend on the target implementation.
    
  • Error messages are logged in the Controller log section of KAS RuntimeIn computer science, runtime (or run-time) describes the operation of a computer program, the duration of its execution, from beginning to termination (compare compile time). Within KAS, runtime also refers to the virtual machine that manage the program written in a computer language while it is running where there is a failure in any related function block.
    
  • Using the KAS Simulator, all pathnames are ignored, and files are stored in a reserved directory. Only the file name passed to the Open functions is taken into account.
    
  • PAC"Programmable Automation Controller" PAC is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical programmable logic controller (PLC). A PAC thus provides not only the reliability of a PLC, but also the task flexibility and computing power of a PC. Additionally, because they function and communicate over popular network interface protocols, PACs are able to transfer data from the machines they control to other machines and components in a networked control system and PDMM/PCMM binary files are not identical. PDMM / PCMM files are big endian, meaning the data structures between the files are different.

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• Be sure to review File Path Conventions so you understand hardware-based functional differences.

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