RSlogix500 MSG instruction

forty

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Mar 2007
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Hello:Guys

I am trying to use Msg instruction to send data from slc5/05 to other slc5/05 by ethernet channel, but the data transfer takes about 2 or 3 minutes to be updated on the target slc.
I activated the SVC(service comunication) but no difference
has any body worked with this function?
I would appreciate any help

thanks
 
how much are you transferring? I msg a few 5 element integer files back and forth between some slc 5/05's and its seems to be almost instantaneous. Is there alot of other traffic on the network? switches or hubs?
 
kurt.brinker said:
how much are you transferring? I msg a few 5 element integer files back and forth between some slc 5/05's and its seems to be almost instantaneous. Is there alot of other traffic on the network? switches or hubs?
Ya. I agree. If it's an independent network, then it shouyld be instantaneous. But more traffic , more delay.
 
Even with a lot of network traffic, 2-3 minutes is way too long. I've had a DH+ network that was loaded down so bad my bits were practically waddling through the plant. But even then, updates were less than a minute apart.

I can only think of 2 things off the top of my head that would cause that kind of latency. Either the MSG is only firing off every 2-3 minutes, or you are failing way more often than you are succeeding.


-jeff
 
Also, if there are other devices accessing the SLC5/05, there is a limit to the number of ethernet connections - 16. If you have 17 devices, one of them may never get in. The way the AB PLC handles ethernet is by ip address order, IIRC. eg. .11, .16, .56, .72, etc. If you have a higher IP, and you max connections, se la vie. That's not well documented, but staying under the max connections definitely keeps you out of trouble. I've also run into this with ENI modules, 10 connections allowed.

A couple of options if that is the case - consolidate your reads such as HMI computers into one PLC rather than multiple.

Or, instead of one PLC "writing", have the other PLC "read". Sometimes that works better, again depending on what you are doing with your network.
 
One thing to keep in mind is how often you really need to send the data. If you are sending all data all the time, that can slow your system down. If for example you are sending some setpoints, you don't need to send them continuously, only when the setpoints change.

Also if you have 4 or 5 MSG blocks going to the same processor, look at grouping that data and cutting down on the number of message blocks.

The other thing to look at if possible is speeding your baud rate up to 230K.
 
Ok guys:
thank you very much for your help
I am already geting data almost instantaniously the problem was that I was writing a msg in one slc, but also reading on the target slc, I though it was necesary but, by Tomalbrigt comments I only need write or read.
other problem was that I was reading continiously with no conditions on read msg rung.
now I put a condtion that is turning on and off the read msg instruction and it is working much better

thanks again guys
 

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