ControlLogix MSG to Offline PLC (ER bit?)

I've got a ControlLogix L61 messaging to a PLC 5/40 via ethernet. The message instruction gives an error code which seems appropriate when the destination PLC 5/40 is disconnected from the network. However, the message error bit (.ER) is not set. Anyone run into this before? This seems a bit odd.

Thanks,

Justin

The MSG .ER bit is only on until the MSG is triggered again. Depending on how you are triggering your MSG, you may rarely see the .ER bit flash on. I usually use XIO MSG.EN to start a short delay timer, then the timer .DN fires the MSG.

More testing done - The .ER bit does flash on. I suppose the odd part is the ER bit only flashes even if you maintain the MSG rung's true condition. I expected the .ER to stay true until I transition the MSG rung from true to false.

Without seeing your precise logic, it's hard to say what you're experiencing. In my experience if you toggle the .EN bit on a ControlLogix MSG instruction, eventually the .ER or .DN bit comes on and stays on until the MSG conditions transition from false to true again.

I prefer to manually set the .TO bit on my ControlLogix messaging to force them to time out, because to wait the default 30 seconds for a TCP connection to time out is too long for some applications.

Ken Roach said:

Without seeing your precise logic, it's hard to say what you're experiencing. In my experience if you toggle the .EN bit on a ControlLogix MSG instruction, eventually the .ER or .DN bit comes on and stays on until the MSG conditions transition from false to true again.

Click to expand...

Tested again with nothing but an XIC test bit on the MSG rung... Regardless of whether I toggle the bit or leave the bit on, the .ER bit is true for just one scan.

I prefer to manually set the .TO bit on my ControlLogix messaging to force them to time out, because to wait the default 30 seconds for a TCP connection to time out is too long for some applications.

Click to expand...

I wasn't aware of the 30 second timeout until today. We'll definitely add some additional logic to account for this.

Thanks for the help.

Regards,

Justin

What version of Logix firmware are you using ? Can you post your program ?

I am very familiar with Logix messaging and have always experienced the .DN and .ER bits remaining true after MSG instruction completion until the MSG instruction is executed again.

Ken,

Well, I slapped my forehead this morning. You are correct regarding the .DN and .ER bits. Yesterday, I missed a rung that unlatches the ER bit in that program.

So the lesson of the day is: do more homework before asking questions.

As always, thanks for your help and contributions to the forum.

Regards,

Justin