PIDAT requires an autotune cycle before it will run?

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Question specific to PIDAT...   in the W502 manual (instructions reference) I find the following statements buried down in the descriptions of all the variables, specifically the variable ATDone, which is the outgoing signal leaving to enable the next instruction to the right on this rung:


ATDone (Autotuning Normal Completion)
This flag indicates when autotuning was completed normally. It changes to TRUE when autotuning
is completed normally and remains TRUE as long as the value of StartAT is TRUE. It is FALSE in the
following cases.
• An autotuning error end occurred.
• Autotuning is in progress (i.e., while the value of ATBusy is TRUE).
• PID control is in progress without autotuning.
• PID control is not in progress (i.e., the value of Run is FALSE).
• The value of StartAT is FALSE.

My question is: How do I get the PIDAT instruction into the state of "PID control is in progress without autotuning"?  If the value of the StartAT input is false, then ATDone will never go true.  However, if StartAT is true, then the instruction is going to start an autotune cycle, which I don't want.  There is no description I can find for how to get it to do "PID control without an autotune cycle having been completed".  The timing diagrams aren't making this apparent either, unless I'm not seeing it.



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Figured this out, just want to be sure it's documented here.

It turns out there are two input variables to PIDAT that are structures, one holds initial setup parameters and the other holds on-going operational parameters.  Things like max/min ranges, some operational preferences, etc.  Well, it further turns out that the default values for the items in these structures are such that the PIDAT instruction is guaranteed not to function correctly.  If you define those two variables, and set up their initial values correctly for your situation, PIDAT should spring to life even if there are no autotune cycles that have been performed.


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