Alarm logic using the "Fault Standard" program

[SiriusMark]

I've been tasked with creating a program to replace an old annunciator panel. We are going to bring all the inputs into a PLC and use a PV+ to replace the panel. I've never actually written a program from scratch, so although I'm comfortable with reading and troubleshooting existing logic, this is a new one for me.

I was looking through the downloads section of the site and taking a look at the Fault Standard project for Rslogix 500. I feel like I am missing something. Assuming you start with a no-fault condition, on rung 0, how does the OTE instruction ever get set, if the XIO that examines B3:6/1 is initially not set. Wouldn't the fault condition come in on I:0/11, and then stop because neither of the XIO's are set?

 

[rdrast]

Notice the bar over the description on B3:6/1? Read that as "NOT FAULT".
It looks like that fault is triggered by I:0/11 dropping out.
On powerup, it would be faulted, requiring a reset.

None of that is logic that I'd actually use, personally.

 

[SiriusMark]

Okay, I can see that. Makes sense. I've never seen a program labelled/used that way, so it didn't even occur to me that was a not sign.