MNL-800 LON SNVT Programming Standards

Issue

MNL-800 LON SNVT Programming Standards

Product Line

TAC I/A Series

Environment

Workplace Tech Tool software (any version)
MNL-800 controller application

Cause

Problems occasionally arise as a result of improper LON SNVT programming and configuration in the MN-800 device application.  These issues include problems with the re-commissioning of the updated controller and potential network variable mismatch situations.

Resolution

 The following standards will prevent these problems from occurring.

  1. Network variables MUST be manually indexed. This prevents issues with the network variables becoming renumbered when application programming changes are made. (See NOTE 1)
  2. Change the application "Program ID" any time network variables are added or removed from an application.  To change the "Program ID" use the WPT Hardware Wizard,  (See NOTE 2)
    1. Select Hardware Wizard from Application Menu
    2. Click [Next] in MicroNet Setup Wizard screen
    3. Change the displayed program ID by entering a different program ID or adding a suffix letter/number. Maximum length is 8 characters.
    4. Click [Finish] to save the changed program ID and exit the MicroNet Setup Wizard.
  3.  In addition, one method of minimizing the need to repeatedly change the "Program ID" as the application is developed and debugged is to add a few extra common SNVT input and output definitions when first creating the application, leaving them unconnected to the application program.  If one of these SVNTs is needed, it is available in the LON network image (XIF file) and it is not necessary to change the "Program ID".
  4. If the MNL-800 controller has firmware version 2.0 (or later) installed, the standard nci network variables do not have to be indexed as the highest numbered SNVTs in the application.  It is perfectly acceptable to number them as the first 17 indexed SNVTs. Note that there are 17 standard network variables (12 nci, 2 nvo & 1 nvi), not just ten nci SNVTs.
  5. SNVT variable names should be limited to 16 characters or less.  Longer names are accepted by the WorkPlace Tech programming tool but the names will automatically be truncated by the LON Network Management tool when commissioning the controller.

In addition, when programming the MNL-800 applications with the WorkPlace Tech Tool version 5.0, or later, it is not necessary to put each MNL-800 application in a separate project.

NOTE 1: If using the WorkPlace Tech Tool version 5.8 or above, you can use the "Object Indexer" to automatically number all the network variables for you.  This tool also includes functions for detecting duplicate SNVT index numbers and for detecting gaps in the assigned index numbers.

NOTE 2: If using the WorkPlace Tech Tool version 5.8 or above, you can set an option in the Hardware Wizard to automatically generate a new ProgramID and reindex the network variables when compiling the application.  Please be aware that this automatic generation of the ProgramID will require the Echelon network image for this device to be updated in any Echelon compatible network management tool.  Please refer to the documentation for the network management tool to determine what actions will be required. For example, if Niagara was used to manage the LON network, then the old shadow will need to be deleted, a new one added, and the device points rediscovered and the device re-commissioned.