Execution

Execution

Math status flags are set for the CV output.
Condition
Function Block Action
Structured Text Action
Prescan
InstructionFirstScan is set
InstructionFirstScan is set
Instruction First Scan
If CVFault and CVEUSpanInv are set, see Processing Faults. If CVFault and CVEUSpanInv are cleared:
  1. CVInitializing is set.
  2. If PVFault is set, PVSpanInv and SPLimitsInv are cleared. See Processing Faults.
  3. The PID control algorithm is not executed.
  4. The instruction sets CVEU = CVInitValue and CV = corresponding percentage.
    CVInitValue is not limited by CVEUmaximum or CVEUMin. When the instruction calculates CV as the corresponding percentage, it is limited to 0-100.
    CVEU equation
  5. When CVInitializing and ManualAfterInit are set, the instruction disables auto and cascade/ratio modes. If the current mode is not Override or Hand mode, the instruction changes to Manual mode. If ManualAfterInit is cleared the mode is not changed.
  6. All the operator request inputs are cleared.
  7. If ProgValueReset set, all the program request inputs are cleared
  8. All the PV high-low, PV rate-of-change, and deviation high-low alarm outputs are cleared.
  9. If CVInitReq is cleared, CVInitializing is cleared.
Instruction first run
ProgOper is cleared.
The instruction changes to manual mode.
ProgOper is cleared.
The instruction changes to manual mode.
EnableIn is cleared
EnableOut is cleared, the instruction does nothing, and the outputs are not updated.
N/A
EnableIn is set
The instruction executes.
EnableOut is set.
EnableIn is always set.
The instruction executes.
Postscan
No action taken.
No action taken.
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