Controller Loop Time Status Registers

The controller loop time status registers provide information on the utilization of the loop time.

Register Name	Units	Data Type	Tag Name	RMC200 Address	RMC75 Address	150 Address
Loop Time Used, Last	s	REAL	_Controller.LoopTimeUsedLast	%MD18.2	%MD20.2	%MD44.2
Loop Time Used, Maximum	s	REAL	_Controller.LoopTimeUsedMax	%MD18.3	%MD20.3	%MD44.3
Loop Time Used, Minimum	s	REAL	_Controller.LoopTimeUsedMin	%MD18.4	n/a	n/a
Loop Time Used, Total	µs	REAL	_Controller.LoopTimeUsedTotal	%MD18.24	%MD20.34	%MD44.34
Loop Time Used, Axes	µs	REAL	_Controller.LoopTimeUsedAxes	%MD18.25	%MD20.35	%MD44.35
Loop Time Used, Programs	µs	REAL	_Controller.LoopTimeUsedPrograms	%MD18.26	%MD20.36	%MD44.36
Loop Time Used, Plots	µs	REAL	_Controller.LoopTimeUsedPlots	%MD18.27	%MD20.37	%MD44.37
Loop Time Used, Comm	µs	REAL	_Controller.LoopTimeUsedComm	%MD18.28	%MD20.38	%MD44.38
Loop Time Used, Overhead	µs	REAL	_Controller.LoopTimeUsedOverhead	%MD18.29	%MD20.39	%MD44.39

Using the Controller Loop Time Status Registers

The controller loop time status registers are useful for determining how much of the loop time is being used. Adding the registers to a plot provides a good visualization. See Plotting the Loop Time for more details.

General Loop Time Status

The following registers are in units of seconds, and help provide general information:

Loop Time Used, Last
The utilization of the last loop time. Including this item on a plot gives a clear indication of the utilization of each loop time. However, it is typically easier to use Loop Time Used, Total, since it is in units of microseconds, which scales better on the plot.
Loop Time Used, Maximum
The maximum utilization of all loop times, in seconds, since the RMC powered up or since this value was reset.
Loop Time Used, Minimum (RMC200 only)
The minimum utilization of all loop times, in seconds, since the RMC powered up or since this value was reset.

To reset the Loop Time Used, Maximum and Loop Time Used, Minimum:

In the Project View, expand Modules and double-click the CPU.
On the Control Loop page, in the Loop Time Usage Statistics section, click Clear.

Detailed Loop Time Status

Including these registers in a plot provides detailed information on the utilization of each section of the loop time. This helps determine how to reduce the loop time utilization if it is high. These registers are in units of microseconds.

Loop Time Used, Total
The total utilization of the last loop time, which is the sum of the following registers.
Loop Time Used, Axes
The loop time utilization of axes, including processing inputs, generating the target profiles, computing the control output, and processing commands.
Loop Time Used, Programs
The loop time utilization of the user programs and Program Triggers.
Loop Time Used, Plots
The loop time utilization of the plots.
Loop Time Used, Comm
The loop time utilization of the communication. This is only the portion of the communications that occurs in the motion loop, which is small compared to the overall communications.
Loop Time Used, Overhead
The loop time utilization of all other items.