800xA OPC Read Data on Demand
It is possible in 800xA to read an array on demand from OPC for once when triggered by, say a button?
I need to display a real array of 320 elements x 6 traces using XY Graph. However since it's polling cylically the communication load is very high. Additioanally the entire workplace becomes extremely slow when the graph is being displayed.
Not really, no. OPC Subscription groups are created automatically by the VB or PG2 graphic elements whenever they are opened on a display.The subscription rate is defined by settings both in the operator graphic and for the individual OPC items.
But perhaps something else is not working correctly. Although 1920 values is quite a lot for one graphic, this does not seem excessive. There should not be any problem getting this data cyclicly from an AC800M controller. If the data does not change much then there should be almost no communication load after the X-Y plot has first populated.
You should be able to adjust the subscription rates both for the operator display or graphic element and also for the OPC items that you are trying to read. Try adjusting these rates to see if your problem goes away or if there is some other issue with your graphic display.
If you are using a different controller ( like AC400 series) then yes, this amount of data could cause a problem and you should try to reduce the subscription rates.