first a couple of questions:
in a couple of places you mentioned "COMPACT-Logix" – but in another place you mentioned "CLX" which is usually an abbreviation for CONTROL-Logix ...
so which is it? ... my reason for asking is that these two platforms do NOT scan their I/O in the same way ...
also ...
is the system that you're working on a "high-speed" process? ...
in simplest terms, does the machinery sound pretty much like a sewing machine when it runs? ...
basic idea: IF (big IF) you're using COMPACT-Logix in a "high-speed" system, then you need to consider the fact that this platform processes its input and output signals by means of a "Dedicated I/O Task" which has a non-configurable priority of 6 ...
so ...
IF you have your other tasks set for higher priorities (in other words – using lower numbers ) ... and ... IF the other tasks are somewhat "burdensome" in terms of their scantime requirements ... and ... IF you're working with a "high speed" process ... then ... you might run into some randomly "missed/skipped" I/O signals once in awhile ...
if your system can't safely tolerate a "missed/skipped" signal once in awhile, then you might want to consider using a CONTROL-Logix platform – rather than a less-expensive COMPACT-Logix ... (specifically, there's no I/O task in the CONTROL-Logix) ...
long ago, I helped a company troubleshoot a COMPACT-Logix based packaging system which would sometimes skip a "go - no go" signal from a custom-made micrometer ... everything worked fine at slow "research and development" speed ... but once they cranked the thing up to "production" speed, random problems would occasionally show up ...
the root problem turned out to be their approach of using "high priority" tasks – at very high execution rates ... they were putting the "pedal-to-the-metal" so to speak – hoping to eliminate the "skipped" signals ... after I had them change their task priorities from settings of 1, 2, and 3 – to settings of 7, 8, and 9 – the problem went away ...
of course they could have simply spent the extra funds to buy a CONTROL-Logix system in the first place – but the savings on the smaller COMPACT-Logix looked too attractive to the powers-that-be ...
DISCLAIMER: since I've retired, I haven't been keeping up with the latest versions of the Allen-Bradley hardware ... it's possible that a newer version might have different operating characteristics than I've just described ... (your mileage may vary) ...
good luck with your project ...
stay safe ... stay well ...