MSG problem whith Micrologix 1100

[jqleandro]

Helo everyone!

I am using micrologix 1100, for communicate through Ethernet IP whith 4 weighing modules,
3 of then are comunicate properly, however the 4th isnt.
I get information of it, but is very slow (40seg like), the other 3 are ok.
I try a lot of test but none have aswers me so far, so now i asking help for the PRO League .
Before you guys thing.
The module dosnt have problems, or the IP adress arent duplicate.
When I erase two weighing modules pair MSG, it work propely (like erase weighing modules 1 and 2 , weighing modules 4 works fine)
I think in begining is some memory duplicate problem, but isnt, I change it, I isolate it, and nothing works.
I let the routine to you guys see if someone can help me.
Weighing modules are full duplex.
I am not using MSG comum formula, but it works fine whith weighing modules 1,2,3 and f4 if I erase modules 1 and 2 MSG.
Below are 2 imagens of isolate part of program

https://imgur.com/a/ka0mIGi
https://imgur.com/z6FWO7U

 

[drbitboy]

I am no expert, but I think the MicroLogix 1100 has a limited number of buffers for MSG instructions. I thought it was four, but maybe it is three, as it seems like all MSG instructions work when you have less than 4 (or 3?).

If that is the case, then the solution would be to configure each of the four MSG instructions to somehow release its buffer.

That said, I would think even if the buffers were not explicitly released, then the MSG instructions would still queue each message to wait for the next available buffer and then the messages would be automatically handled in a round-robin fashion, so maybe it is something else e.g. number of open TCP/IP connections.

So whether it's buffers or connections or something else, it does appear to be a resource limitation.

 

[cardosocea]

I tend to create a rolling scheme for triggering messages where one message is only active if the previous one is done or in error. This guarantees that you won't be stretched too thin like this.



How fast do these need to be updated?

 

[Ken Roach]

Welcome to the PLCTalk forum community !

The MicroLogix 1100 has a total of 12 message buffers: 8 incoming, and 4 outgoing.

If this were my system, I would write a simple state machine that triggered one message at a time.

Or, configure your logic to alternate between Read and Write messages to each weigh scale device, so that you have a maximum of 4 messages active at a time.

 

[johnd_125]

The example for MSG to scale controllers, and which I copied on several projects, cycles through the MSG instructions. It looks like you are basically enabling a message instruction any time it is not enabled? So, you are hitting nearly all them at the same time, all the time? That might be your issue, you are just executing too many MSG instructions at once and bogging things down.

Try using a timer to execute your message instructions, one at a time, ~100 ms or so apart and see if that helps.

Also, see if your specific scale controller has a sample Logix 500 plc program. I'll attach a sample program for MT IND570 controller.