Allen-Bradley LOGIX 5000 Reference Manual page 64

Chapter 1 Process Control Instructions
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Output Parameter Data Type
EnableOut BOOL
Out REAL
DeltaT REAL
Status DINT
InstructFault (Status.0) BOOL
LeadInv (Status.1) BOOL
LagInv (Status.2) BOOL
TimingModeInv (Status.27) BOOL
RTSMissed (Status.28) BOOL
RTSTimeInv (Status.29) BOOL
RTSTimeStampInv BOOL
(Status.30)
DeltaTInv (Status.31) BOOL
Description
The LDLG instruction supports one lead and lag in series. The instruction also
allows configurable gain and bias factors. The LDLG instruction is designed to
execute in a task where the scan rate remains constant.
The LDLG instruction uses this equation:
with these parameter limits:
Parameter
Lead
Lag
Whenever the value computed for the output is invalid, NAN, or
instruction sets Out = the invalid value and sets the Math overflow status flag.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Description
Enable output.
The calculated output of the algorithm. Math status flags are
used for this output.
Elapsed time between updates. This is the elapsed time in
seconds used by the control algorithm to calculate the process
output.
Status of the function block.
The instruction detected one of the following execution errors.
This is not a minor or major controller error. Check the
remaining status bits to determine what occurred.
Lead < minimum value or Lead > maximum value.
Lag < minimum value or Lag > maximum value.
Invalid TimingMode value.
For more information about timing modes, see Function Block
Attributes.
Only used in real time sampling mode. Set when
ABS | DeltaT - RTSTime | > 1 (.001 second).
Invalid RTSTime value.
Invalid RTSTimeStamp value.
Invalid DeltaT value.
Limitations
LowLimit = 0.0
HighLimit = maximum positive float
LowLimit = DeltaT/2 (DeltaT is in seconds)
HighLimit = maximum positive float
INF, the