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General Category => Do-more CPUs and Do-more Designer Software => Topic started by: Barnic on September 03, 2026, 11:54:32 AM

Title: PID View: Cannot Write SP to PLC in manual mode
Post by: Barnic on September 03, 2026, 11:54:32 AM

EDIT: I found a ST1 ($On) contact controlling a PINIT instruction that was controlling the Setpoint. Corrected to a ST0 ($FirstScan).

Hello,
   In PID view, while in Override mode -> manual, the SP cannot be written to the PLC under the "variables" area. However, the Output can be. Is there a reason for this? Thanks

Title: Re: PID View: Cannot Write SP to PLC in manual mode
Post by: franji1 on September 03, 2026, 01:26:10 PM

The .SP is being written by Designer, but it's probably being overwritten somewhere in your ladder logic?  Bring up a Cross Reference View and see where yourpid.SP is being used as an OUTPUT.

Realize that modifying the SP of PID loop that is in Manual mode has no affect on the loop's .Output (whether the .SP is being modified in Ladder or via the PID View).  In Manual Mode, you have direct control of the .Output variable of the PID (the PID instruction is not writing to it like it does in Auto mode).

Title: Re: PID View: Cannot Write SP to PLC in manual mode
Post by: Barnic on September 03, 2026, 04:58:21 PM

Thanks, I had just discovered what you had said right before you responded. The ladder was overriding it. Thanks again!