All,

PCS 7 V9.0 SP3

To troubleshoot a communication issue I deleted and replaced the analog input driver (PCS7AnIn) and module drivers for a field instrument.  The original input driver was in OB33, but the replacement is marked for insertion into OB100 which generated a warning during compilation (attached).

In object properties I see PCS7AnIn is "To be inserted in OB100", so this seems normal, but I have inserted this block type before and I don't remember seeing this compilation warning.  I also don't see why it would generate a warning if that's where all blocks of this type get inserted.  It seems like a problem, because we almost never power down our CPUs, so it seems like this block will not be called.

I have a vague understanding of how OBs work, but not in great detail.  I see how I could insert it into a different OB, but I've never done that before and I try not to do things I don't fully understand.  It is very important that the CPU does not lose the ability to download changes in run (if I make a mistake), but we also need this block to be called cyclically without powering down the CPU.

Am I misunderstanding how OB100 works? Will the block be called eventually even if we do not warm restart? If not, why is this the first time I've needed to assign a different OB (I've probably added a dozen PCS7AnIn blocks to the project, all are now in a cyclic interrupt OB, and I have never assigned a different OB or warm restarted just to call a block in OB100).

Any help is appreciated--I am now avoiding a PLC download until I am sure I understand the situation and the correct next step.