Niagara enhanced MS/TP Protocol

Beginning with Niagara 4.12, QNX-based controllers that are licensed for the BACnet MS/TP driver use enhanced MS/TP (emstp) processing that is provided by the RS-485 co-processor. Prior to the above release, processing for MS/TP communications is provided on the controller CPU. With this update, the enhanced ms/tp processing mode is the default condition when using this protocol, however, you can revert to the legacy mode by configuring the BacnetMstpPlatformServiceQnx properties.

Enhanced MS/TP protocol benefits

If you are using multiple MS/TP trunks and large numbers of MS/TP points, your controller CPU usage may be very high, contributing to slow performance. Enhanced MS/TP provides a significant benefit by moving the default MS/TP engine to the RS-485 co-processor. This new architecture makes it possible to take a substantial load off of the CPU and provide overall controller performance improvements. Depending on your configuration, improvements may include increased communications reliability and more responsive graphic views.

Legacy mode processing

If you want or need to use the legacy (CPU-based) processing mode, you can do that by configuring properties that are available in the BacnetMstpPlatformServiceQnx component. For additional information, refer to “Reverting to legacy MS/TP processor” in the “Platform Services” chapter.

Furthermore, with some additional configuration, it is possible to capture diagnostic data.

MS/TP communication statistics

You can access statistics that may be helpful in diagnosing problems. Refer to the “Tokens” topic in the components section of the Niagara Engineering Notes to view the statistics that are available when you are using an MS/TP communications network port.