CompactLogix DF1 Messaging to MicroLogix

I wanted to double check something, and make sure I'm not just overlooking an obvious solution. I have a system that will be running an L35E CompactLogix at a master site. The L35E needs to message six remote MicroLogix PLCs using DF1 over radio modems. Am I correct in thinking I will need one MSG instruction in the L35E for each piece of information I need, compared with the SLC/MicroLogix method of MSGing a block of data at one time? I've done a couple CompactLogix jobs before, but this is the first one with remote communications, so I want to make sure I'm not just missing something here. Thanks.

Joe

Well, apparently I was overlooking something obvious. I re-read the section on MSG instructions in the General Instructions reference manual, and apparently you just need to create an Array tag, and set up your MSG to look at the first register in the SLC/MicroLogix, the Array tag, and the number of registers to transfer. Easy enough.

A little bit of advice that is not necessarily applicable to your immediate needs; when you are doing CIP Tag Read/Writes between Logix-family controllers over DF1 Radiomodem protocol, I recommend using Unconnected Messaging.

Unless your radiomodem system is a true full-duplex system or handles collision-avoidance very well, the extra messages that open and close CIP Connections might interfere with the other messaging on your network. The /DN bit for a Connected CIP Tag Read/Write MSG instruction comes on before the Connection is actually closed.

Because you are doing messaging to MicroLogix controllers, which use only the unconnected-type PCCC messaging, this won't be a problem.

Ken,

Thanks for the advice. So far, we haven't gotten into any Logix to Logix communications over radio, but it may happen eventually. I'll keep this filed away for future reference. Thanks.

Joe