Compact/Control Logix RPI Recommendations

So we have been using compact and control logix for some time now and no one has looked into the effect of RPI on a module by module basis.

The modules currently use their defaults as they are inserted into the rack. We use 1769-IA16 modules quite often and the RPI of the modules is defaulted at 20ms. Analog modules I believe are typically defaulted to 80ms.

We are reading in running contacts from motors, limits, door sensors, level indicators, etc... Analogs are typically 4-20ma valves, flowmeters, vfd's, etc...

Does anyone know of a place to find guidelines in regards to required speeds reading in discrete/analog I/O signals in an automation environment?

Thanks Much

this might not be the answer that you're looking for – but it's pretty important stuff IF (big IF) you're working with fast/high speed applications ...

as for analog input signals – the RTS (Real Time Sample rate) is probably more important than the RPI (Requested Packet Interval) ...

http://www.plctalk.net/qanda/showthread.php?p=391975&postcount=1

and if you're working with COMPACT-Logix (as opposed to CONTROL-Logix) - and if you're using Periodic Tasks with priorities higher than 6 (in other words, priority settings with numbers lower than 6) - then you need to know about the COMPACT-Logix system's Dedicated I/O Task ...

http://forums.mrplc.com/index.php?showtopic=26162&p=125399

and if you're working with CONTROL-Logix (as opposed to COMPACT-Logix) then probably would be interested in the COS (Change Of State) capability of your digital input modules ... this is usually turned ON by default – which means that your RPI settings don't really need to be set "fast" in order to give you "fast" updates ...