Modicon PLC <-> Magelis HMI momentary button reliable?

I’ve inherited a project where nearly all control is via momentary buttons in Magelis HMI pulsing one bit to turn something on and pulsing another to turn it off. The Modicon PLC never writes these bits, and if they did happen to be left on somehow (HMI failed to turn off at end of momentary button pulse), they could cause unexpected starts.

I wouldn’t normally program that way. Instead, the HMI would latch the control and PLC unlatch it to ensure it gets unlatched regardless of communication failure in the middle of momentary pulse, HMI shutdown/freeze, etc. I searched the internet a bit and didn’t run into anything on this particular PLC/HMI combo. Do any of you know if there is anything special about the Modicon - Magelis pair that makes this more reliable than other HMIs and PLCs?

I suspect not, but would be glad to be corrected. Production personnel have reported behaviour that would suggest some of these momentary controls may have remained latched on occasion. If there isn’t something special that makes this a reliable control method with Modicon & Magelis, I’ll need to update it all. (Working with Magelis is a great way to increase appreciation for Ignition!)

I haven’t used any Modicon products in several years, so I can’t be sure, but if it’s using ModbusTCP as the protocol, the answer is no.

Thanks Phil! That makes sense and this setup is using Modbus TCP.

You may be interested in this thread.