MicroLogix 1400 ethernet communication with CompactLogix

What is the best message instruction to use between the MicroLogix 1400 and the CompactLogix L32e?

Coming from someone who has done this exact thing before and assuming you are doing this over ethernet, I recommend that you put all the messaging routine inside the ML1400. On the Logix5000 side you will want to go under menu Logic>Map PLC/SLC Messages and associate your tags with SLC style memory files.

On the ML1400 side you will simply have a subroutine with the standard MSG instructions. Just have it poll a read and a write cyclically. I usually base it purely off the handshaking signals and do not introduce any time delays.

The reason I recommend putting this routine in on the ML1400 is that I ran into a situation where if the ML1400 lost power for any reason it would take 9 minutes to re-establish communication between the two. Something gets stuck on Logix5000 side that has a very long timeout. I spent a day and a half trying to work it out to no avail. Once I moved the messaging routine to the ML1400 it would re-establish comms in under 20 seconds.
 
It's actually simplest to put the MSG instruction in the CompactLogix, since you can directly enter an SLC/PLC style Data Table Address into an MSG instruction's remote address field in RSLogix 5000.

If you're going to put the MSG instruction in the MicroLogix, you must configure an array tag (usually an INT[x] type) in the CompactLogix to be equivalent to an SLC Data Table. This is configured from the main menu: Logix -> Map PLC/SLC Messages.

Let's say you have an INT[10] array named "MicroData[x]" in the CompactLogix, mapped to Data Table 10.

From the MicroLogix MSG instruction perspective, this is "N10:0-9".

This "mapped array" serves as the data source for Reads, and the data destination for Writes.

Use the "500 Data Table Read/Write" message type selection in the MicroLogix, not the 485CIF or PLC-5 read/write or the CIP Generic.
 

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