Overview Of Timing Modes - Allen-Bradley Logix5000 Reference Manual

TimingMode = 0
Periodic Timing
Determine Task Type
Periodic Task
DeltaT = Task scan time
If DeltaT > 0, the instruction executes.

Overview of Timing Modes

The following diagram shows how an instruction determines the appropriate
timing mode.
Determine Time-base Mode
TimingMode = 1
Oversample Timing
DeltaT = OversampleDT
If DeltaT < 0 or DeltaT > 4194.303 s the
instruction sets DeltaT = 0.0 and sets the
appropriate bit in Status.
If DeltaT > 0, the instruction executes.
Event or Continuous Task
DeltaT = Elapsed time since last execution
If DeltaT > 0, the instruction executes.
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Function Block Attributes
TimingMode = 2
Real Time Timing
DeltaT = RTSTimeStamp - RTSTimeStamp
n
If DeltaT > 0, the instruction executes.
If |RTSTIME - DeltaT| > 1, the instruction sets RTSMissed
bit in Status.
Appendix B
n-1
665