Read data from Micro850 to Compactlogix

[829]

Hello,

I am new to both the compactlogix and messaging. I have 30 tags (int, dint, and real data types) in a micro850 that I need to read from a compactlogix plc. I am currently individually messaging each one of these points and I am wondering if there is a better way. Compounding this issue is that I have multiple 850 sites to retrieve data from, so I need to be able to scale this up from a one to one communication to a one to many communication, where one compactlogix plc will be reading 30 different data point from 20 different 850Â’s. Each 850 site will have the same tags, but obviously different values based on its location. I was able to bring in 5 sites, but on the 6th site, the L33 locks. I called Rockwell and they recommended one large routine, instead of one routine per site, but that seems like a nightmare from a support perspective. Have any of you performed anything like this before and if so, do you have any sample code you could provide? Does anyone have any recommended best practices here? Thank you.

 

[829]

To clarify, in my above example, I will be reading 600 different tags. The tags are the same in each 850, but when I bring them back, I am naming the tags with the site location name.

 

[drbitboy]

I assume this is explicit messaging over Ethernet/IP?

One way to speed it up would be to pack (COPy) the 30 tags into a single entity (e.g. array of INTs) on each Micro850, transfer the array of INTs on the 850 to an array of INTs on the CompactLogix, then unpack the INTs back to their original form. That would require new code on the Micro850s to pack the array, but at least it would be universal, and then new code on the CompactLogix to unpack the array, which might involve some byte- and/or word-swapping. It is not a small task, but it is relatively trivial as it mainly involves bookkeeping of the bits.

On the CompactLogix, I am fairly certain the Micro850s' data, including connection parameters, will be best encapsulated in an array of UDTs, and the code itself should be an AOI. An outer loop, with each pass triggered by a timer after a successful or failed transfer, will step through the array of UDTs to get the next UDT to poll. You might even be able to run four or five of those AOIs at once, with a queue (FIFO?) of indices into the UDT array to select the next Micro850 to poll.

 

[829]

Yes, etherenet via cellular communication.

 

[drbitboy]

https://literature.rockwellautomati...ure/documents/pm/1756-pm012_-en-p.pdf#page=25