Allen Bradley Ethernet/IP Mapping Size Limit?

[Chris Elston 78]

On 8/23/2022 at 6:14 AM, BigTomek said:

Do you have any new news about this topic.Now I am in same situation.How do you solve this problem?

I have NOT gotten Large Forward Open to work with ANY Compact Logix. I was told that a Control Logix and 1756-EN2T(R) can do it, but I haven't a project that requires a Control Logix to confirm it. At this time, I agree with @pturmel above, I have not been able to get any Rockwell products to support this feature of Ethernet/IP.

[Mark- 17]

 

On 12/9/2020 at 5:56 AM, Mark Short said:

FWIW my experience with the Large Forward Open service and Allen Bradley devices is that the Logix range will only support a connection size of about 4000 bytes...

I had the same results, 4003 bytes.

 

Edited 24 Aug 2022 by Mark-

[pturmel 157]

Yes, you can use ~4000 byte buffers with modern logix hardware and Class 3 messaging.  Nowhere will Logix allow more 500 bytes payload in a Class 1 traffic.  I/O connections and producer/consumer tags are Class 1 (payloads are delivered via UDP).  I have had success with large forward open I/O connections with Omron and Keyence products (max varies by product, but is typically 600 bytes or 1440 bytes).

Rockwell simply is not keeping up with the competition for a protocol they invented. ):

(BTW, Micro800 doesn't do Class 1 I/O connections at all.)

[Ray Shaw 0]

Not that it helps anyone, but in looking for MSG data limit sizes for an unrelated reason, I found the following.

You can use a message to send a large amount of data. Even though there are network packet limitations (such as 500 bytes on ControlNet and 244 bytes on DH+), the controller can send a large amount of data from one MSG instruction. When configuring the message, select an array as the source/destination tags and select the number of elements (as many as 32,767 elements) you want to send. The controller automatically breaks the array into small fragments and sends all of the fragments to the destination. On the receiving side, the data appears in fragments, so some application code can be required to detect the arrival of the last piece.

so...32767 elements seems to be the limit. How it applies in this thread is probably irrelevant, but this thread was helpful to me for my research, so I figured I'd throw this in if anyone ever needed to reference what I found. Page 107 on the following pdf, https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1756-rm094_-en-p.pdf

Edited 8 Jun 2023 by Ray Shaw
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[pturmel 157]

On 8/24/2022 at 9:36 AM, pturmel said:

BTW, Micro800 doesn't do Class 1 I/O connections at all.

I should note that this is no longer true.  The relatively new 850E and 870E added this capability.