Allen-Bradley LOGIX 5000 Reference Manual page 53

Process Control Instructions
Output Parameter Data Type
EnableOut BOOL
Out REAL
DeltaT REAL
Status DINT
InstructFault BOOL
(Status.0)
InFaulted (Status.1) BOOL
DeadtimeInv BOOL
(Status.2)
TimingMode BOOL
(Status.27)
RTSMissed (Status.28) BOOL
RTSTimeInv BOOL
(Status.29)
RTSTimeStampInv BOOL
(Status.30)
DeltaTInv (Status.31) BOOL
Description
The DEDT instruction uses a data buffer to store delayed data, thereby allowing
any length deadtime desired. The DEDT instruction is designed to execute in a
task where the scan rate remains constant.
To use the DEDT instruction, create a storage array to store the deadtime buffer
to hold the samples of (In x Gain) + Bias. The storage array should be large enough
to hold the largest desired deadtime, using this formula:
StorageArray Size Needed = Maximum Deadtime (secs) / DeltaT (secs)
Servicing the Deadtime Buffer
During runtime, the instruction checks for a valid Deadtime. Deadtime must be
between 0.0 and (StorageArray Size x DeltaT).
If the Deadtime is invalid, the instruction sets an appropriate Status bit and sets
Out = (In x Gain) + Bias.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Description
Indicates if instruction is enabled. Cleared to
false if Out overflows.
The calculated output of the deadtime
algorithm.
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.
In health is bad.
Invalid Deadtime 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 millisecond.
Invalid RTSTime value.
Invalid RTSTimeStamp value.
Invalid DeltaT value.
Chapter 1
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