UNC-520 heartbeat LED had no activity


The resolution of this article has many complex steps that may result in unforeseen results if not performed correctly. If you are at all unfamiliar with the requirements, please contact Product Support Services for assistance.


UNC-520 heartbeat LED had no activity but the UNC appears to be running without issues. 

Product Line

TAC I/A Series


I/A Series Universal Network Controller - UNC-520


The UNC CPU idle is at 0% which resulted in the UNC heartbeat LED not having any activity (always off). 
In this case,  this is caused by changing the ControlEngineService executionFrequencies to faster values and objects' executionParameters frequency set to faster or fastest. The station is using large amount of CPU resources. 


To correct this make the following adjustments: 

  1. In the ControlEngineService properties, Config tab, change the executionFrequencies back to the default values of fastest at 500ms, faster at 1s, normal at 2s and slower at 5s
  2. Change the objects' executionParameters frequencies back to the default setting of normal. You can used the AdminTool object to perform a search and replace and changed all the executionParameters frequencies to normal. 

There may be a need to change these values from the default values to optimize the UNC performance. Refer to the Niagara Capacities Engineering Notes for details. You should contact Product Support if you are unsure of these settings.