Plotting the Loop Time

To clearly visualize the loop time usage of the RMC, you can add the following Controller Loop Time Usage Registers to a plot to monitor the loop time:

Units in seconds

Loop Time Used, Last

Loop Time Used, Maximum

Loop Time Used, Minimum

Units in microseconds

Loop Time Used, Total

Loop Time Used, Axes

Loop Time Used, Programs

Loop Time Used, Plots

Loop Time Used, Comm

Loop Time Used, Overhead

To add these registers to a plot:

In the Plot Template Editor, create a new plot template or choose an existing plot.
Choose Custom Plot.
In the Plotted Data Items table, click New Quantity.
On the Registers tab, browse to Controller, Loop Time, and choose the desired Loop Time Used registers.

When trending a plot, you can see how the loop time usage varies. When commands are issued, the loop time will typically increase significantly for that loop time. If the total loop time used occasionally exceeds the set loop time by a small amount, there will typically be no adverse effects. Small loop time overages will be reported in the Event Log as a warning, which can be filtered using the Event Log filter settings.

It is very important that a single control loop execution or the accumulated carryover from consecutive loops does not exceed the loop time by more than 100%. The RMC will report an error in the Event Log if the loop time overage or cumulative loop time overage exceeds 80%. For more details, see the Loop Time topic.