Help with sending inputs/outputs from one compactlogix to another

stu

Member
Join Date
Aug 2005
Location
England
Posts
773
Hi
I have a job to do which is to have a call button and a sounder on either end of a line so if the operator needs assistance they can press the call button and the sounder goes off both ends of the will have this option
Either end of the machine has a compactlogix via Ethernet

How do I send the msg bits on Rslogix 5000 ? I've seen you Add the one Plc to Ethernet tree and add a read msg instructions but can you move inputs and outputs ?
Also if I do it that both ends have a call button and a sounder will both plus need read instructions??
Any help would be fantastic
 
Instead of using MSG instructions, I would lean toward have a produced/consumed tag in both machines. Then the data from one will appear in the other without extra logic to control it.

Another option is to allow each CPU to monitor the required I/O from the other CPU with a listen only connection.

The drawbacks to either of these:
1. There will be constant Ethernet traffic added to the network between the two machines.
2. If there is a problem with the connection, the I/O status LED will flash. That can draw unwanted attention.
3. You don't get to control this once set up, it just works all the time at the rate you dictate up front.

Using MSG instructions will let you have flexibility (if needed) to program when and how often to exchange the data. I would favor having a read and write message in one PLC but I could be convinced to have a read message in both PLCs. If you are writing data, just make sure that the destination tag in the other PLC is well commented.
 
It is fairly straightforward to configure Produced/Consumed Tags in a CompactLogix.

I like to set up a larger array than I will likely need, so that I can expand the functions without re-creating or re-configuring or doing a fresh download of the program.

You can start with the RA User Manual:

https://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm011_-en-p.pdf

or you like, watch one of a dozen YouTube videos; search "Produced Consumed Tags RSLogix 5000"
 
Ive just watched a YouTube video and seen that produced and consumed tags is a great tool ,I seen that you need the processor you are communicating to in the IO tree @ both ends
And you use udt say an array for the future use,
I can see that teals and dint are common with the use but is it common for bools to be used
Like processor 1 I:3/1 -| |- to (UDT ) produced to processor 2 O:4/9
 
You don't produce/consume physical I/O. Each controller should control it's own I/O.

You would produce/consume a DINT array, for example. Your producer could populate DINT[0] with your producers local input module, then at the consumer end, use DINT[0] to control the consumers output.

XIC DINT[0].0 OTE Local:2:O.Data.0
 
I take it you dont have to use/setup user dinfined tags you can just use a tag used in both plc ?
 
You don't have to use UDT, but you can if you wish.

The benefit is that you can package all sorts of data together and transfer it all as one tag. You can put BOOL, DINT, REAL, etc all together in one UDT tag. As Ken mentions, you can create some extra tags for "future use". But if you are just working with BOOLs it isn't necessary.

The minimum size for a Produce/Consume tag is a DINT so you can package your BOOLs into one or more DINTs.

One other question......the I/O you want sent to the other controller...Is it originating from a local I/O module for that controller, or is it connected over EtherNet/IP?

OG
 

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