How Many SLC 5/05 can a ControlLogix Message at the same time

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Hello, Everybody.

Could somebody tell me how many slc 5/05 a ControlLogix can communicate with. I mean, can I do Ethernet Messaging to 162 slc 5/05 controllers simultaneously?

Thanks in advance!

Enrique Marín

 

[vagler]

You can but not with only one message instruction you would have to use separated instructions for each controllers. (The messages will go to a queue and they will stay there until the controllers scans their message so is hard to say is simultaneous)

You could use only one instructions and change the path to send the messages at different times.

Check this out: http://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm012_-en-p.pdf

 

[rguimond]

Any number of MSG instructions can be used, but only one can be executed at any given time. However, they can be executed very quickly.

I always set up my MSG so they cascade. The first MSG is initiated by a first scan or by a DN, ER or TO bit set by the very last MSG. Any of these conditions OTUs (unlatches) the EN bit on the last MSG and enables the first MSG.

The first MSG is OTU and the second one is ENabled whenever a DN, ER or TO bit for the first MSG is made.

It continues along this path until the last MSG is reached.

I can post an example, if you like, from a ML1100 controller.

Using Ethernet communication and only reading enough words to get the job done allows this to happen really fast.

Some programmers like to introduce a delay between MSG, but I've never had to do this.

 

[rguimond]

After posting, I was curious about just how fast the MSG were executed, so I set up a timer controlled by a bit that is latched when the first MSG is ENabled and unlatched when the last message is DoNe. I found that it takes about 0.127 seconds to execute 7 MSG reading a single word from 7 different PLCs. Five of the PLCs are ML1200 with NET-ENI adapters and two are ML1100.

Another ML1100 reads a single word from each of two SLC 5/05s. The execution time for these MSG is about 0.150 seconds.

I should note that I'm not using managed switches for the Ethernet network and that there is a LOT of network traffic, although nothing is super-critical.

 

[OkiePC]

I think you'll run into a limit on the number of TCP connections. It's my understanding that each unique IP address is going to take up a connection, and that a 1756-ENBT module is limited to 64 or 128...some of which may be used for other things.

There may be some simple things you can do to release those connections so they can be re-used in order to acheive your goal.

I would definitely contact RA support and describe your needs before you start the work of implementing this.

I am a novice with Controllogix, so I could be wrong. Hopefully one of the experts will confirm or clarify my concerns.

 

[daba]

In answer to OkiePC's post - for every MSG instruction, there is a check-box to "Cache Connections".

If you un-check this, then the connection is established, the message is executed, and then the connection is released.

For a substantial amount of messaging, then cascading them (as already described) is the way to go, and disabling the "Cache Connections" on all of them. That way all your communications will only use one connection through the Comms module.

It's a little slower doing it this way, but preserves your connection resource.

 

[rguimond]

In answer to OkiePC's post - for every MSG instruction, there is a check-box to "Cache Connections".

If you un-check this, then the connection is established, the message is executed, and then the connection is released.

For a substantial amount of messaging, then cascading them (as already described) is the way to go, and disabling the "Cache Connections" on all of them. That way all your communications will only use one connection through the Comms module.

It's a little slower doing it this way, but preserves your connection resource.

It may improve performance to dedicate a few of the 5/05s as "data collectors". If you have 162 5/05 on the network, have six 5/05s that collect data from 26 other PLCs. Use the Controllogix to poll only the six "data collectors"