When an operator or script modifies an output variable, the alternate value table (ALT ) gets modified and the values written to the output device get rerouted to come there.
The alternate value is viewable in RT Viewer and in HMI Display. See Get/Set Value Tab (Upper Right Pane), Variable Control Buttons, and y Vs Time Plot.
When an output RTDB variable is modified by an operator using RT Viewer or HMI Display, the operator flag associated with that variable is set. RT Viewer can be used to clear this flag, rerouting data written to the output device to come from the CVT again. See Get/Set Value Tab (Upper Right Pane).
When an output RTDB variable is modified by a script program (see Scripts...), the alternate flag associated with that variable is set. RT Viewer can be used to clear this flag, rerouting data written to the output device to come from the CVT again. See Get/Set Value Tab (Upper Right Pane).
If either the operator flag or the alternate flag is set, data written to the output device will be written from the alternate table. If both are clear, data written to the output device will be written from the current value table.
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Modification of an Input Variable |