Tags, Data Types and Other Data

  • As you organize, add, or delete members of a User-Defined Data Type, the software adjusts the associated tag members and values accordingly so that remaining members retain their values.
  • In the tag browser, click the >> button to display the tag filter. Use the tag filter to display unused tags or tags of a particular data type.
  • The tag browser filters tags in some situations. If you don't see a tag you expect, change the tag filter.
  • In version 15, the Tag Editor added support for New Window.
  • You can use arrays to do indirect addressing. RSLogix 5000 supports arrays of one, two, and three dimensions.
  • You can create a recipe by creating a new data type and then creating a tag which uses that data type. Your new data type can contain descriptive field names.
  • RSLinx uses memory in a Logix controller to read data values. Use the following equation to estimate the memory needed: (1.5Kbyte + (Number of individual tags * 45 bytes) + (Number of array or structure tags * 7))
  • The Watch Pane, located below the language editor window, provides monitoring for all tags referenced in the active routine window.
  • You can trend a tag by right-clicking the tag and choosing "Trend Tag ".
  • You can find all occurrences of a tag by right-clicking the tag in logic and choosing "Find All ".
  • Logix controllers are optimized for the DINT and REAL data types. Use these data types to avoid conversion overhead and optimize performance.
  • You can optimize the communication performance of acquiring data from Logix controllers by consolidating multiple data values into a User-Defined Data Type (UDT) or array.
  • Indexed references to array elements add additional scan time overhead to the application. Use single dimension arrays whenever possible.
  • When building a User-Defined Type (UDT), locate all bits or BOOLs adjacent to each other to minimize the amount of controller memory required to store the data.
  • RSLogix 5000 automatically creates controller tags when you create an input or output module. You can reference these tags directly in your logic.
  • Use alias tags to assign names to specific input/output data and/or to provide a short alternative to lengthy structure member names.
  • Avoid pointing one alias tag to another alias tag to ensure the application maintains the appropriate references after an upload.
  • Avoid pointing multiple alias tags to the same base tag to ensure the application maintains the appropriate references after an upload.
  • Controller tags apply to the entire controller and can be referenced by any program. Program tags apply only to individual programs. This means program tags can have the same names in more than one program, allowing programs to be copied and reused.
  • You can reorder the columns in the tag editor by clicking on the title and dragging it to a new position.
  • All tag names are downloaded and resident in the controller along with your logic.
  • You can export (and import) tag definitions to a comma separated value (CSV) file and manipulate them using external tool, e.g. spreadsheet, text editor.
  • For tables of bits (BOOL), use a DINT array to ensure full access via the file and diagnostic instructions COP, DDT, FBC, etc.
  • In a safety controller, standard tags in a safety mapped relationship follow safety restricted states. For example, a standard tag mapped to a safety tag is read-only in a safety locked state.
  • The order of members within a User-Defined Type affect the memory size of the data type. Within the UDT, keep members of the same data type together.