How can two controllers of different types be assigned the same program ID?

Issue

How can two controllers of different types be assigned the same program ID?

Product Line

TAC Vista

Environment

  • Xenta programmable controllers
  • Xenta 280, 281, 282, 283, 300, 301, 302, 401, 401:B
  • Menta

Cause

This is because of how the LonMark Standard program ID is generated.

Resolution

The LonMark standard for generating the Program IDs is based on what SNVTs are present in the application. Two .MTAs may have the same types and number of SNVTs included in the LonMark set, regardless of controller type, and therefore the program IDs can be generated the same.

The other possibility is that two programs just happen to get the same IDs because there are only so many possible combinations of SNVTs that 255 combinations reduced the number of unique IDs. Using the check box option "XIF-Header generated according to LonMaker standard" will use only 255 (or FF in Hexadecimal) combinations of IDs. By un-checking the "Generate Program ID's according to LonMark Standards", 65535 (or FFFF in Hex) combinations can be assigned. This makes it much more likely that the IDs will not conflict.

Adding a dummy SNVT to one application and regenerating the ID (leaving the LonMark option checked), is another option to resolve the conflict.