Process Control Instructions
54 Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
The deadtime buffer functions as a first-in, first-out buffer. Every time the
deadtime algorithm executes, the oldest value in the deadtime buffer is moved into
Out. The remaining values in the buffer shift downward and the value ((In x
Gain) + Bias) is moved to the beginning of the deadtime buffer. A new value that
is placed in the deadtime buffer appears in the Out after Deadtime seconds.
The number of array elements required to perform the programmed delay is
calculated by dividing Deadtime by DeltaT. If Deadtime is not evenly divisible by
DeltaT, then the number of array elements and the programmed delay are
rounded to the nearest increment of DeltaT. For example, to find the number of
array elements required to perform the programmed delay given Deadtime = 4.25s
and DeltaT = 0.50s:
4.25s / 0.50s = 8.5
rounds up to 9 array elements required
The actual delay applied to the input in this example is:
number of array elements x DeltaT = programmed delay or
9 x 0.5s = 4.5s
Runtime changes to either Deadtime or DeltaT change the point in which values
are moved out of the buffer. The number of elements required to perform the
programmed delay can either increase or decrease. Prior to servicing the deadtime
buffer, the following updates occur:
If the number of required elements needs to increase, the new buffer elements are
populated with the oldest value in the current deadtime buffer.
If the number of required elements needs to decrease, the oldest elements of the
current deadtime buffer are discarded.
Instruction Behavior on InFault Transition
When InFault is true (bad), the instruction suspends execution, holds the last
output, and sets the appropriate bit in Status.
When InFault transitions from true to false, the instruction sets all values in the
deadtime buffer equal to In x Gain + Bias.
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See Common Attributes for operand-related
faults.
To Next Page
Loading...
Need help?
General
