Performance Comparison - RSLinx OPC versus AdvancedHMI ControlLogix Driver

[Archie]

I put together a quick performance test to see how the response time of the AdvancedHMI driver compared to RSLinx, In this test I created as simple PLC program with a free running timer. Using AdvancedHMI I created a subscription to this timer tag with a PollRateOverride of 0 which would make it go as fast as it possibly could. I then allowed it to return 100 values. By subtracting the current value read with the last value read, it would give a reasonable time lapse. Over the 100 reads, I averaged the values. I then repeated the same using RSLinx. Here are the results:

Average Read Time for EthernetIPForCLXCom = 6.1ms
Average Read Time for RSLinx = 7.8ms

That equates to a 22% increase in performance when using AdvancedHMi verus RSLinx.

[bachphi]

Did you leave default settings on RSLinx side? like PollMessages

[Archie]

I set the UpdateRate within the SubscriptionState object to 0, which should be telling it to update as fast as possible.

[bachphi]

I thought you configured an opc topic in Rslinx, and in the DataCollection tab, there is a number of settings that would affect its performance.

[Archie]

I'm not sure if that applies since I am creating direct subscriptions to the tags using the topic and not utilizing any kind of data collection functionality. But I could be wrong because I do not consider myself on OPC expert by any means. I checked that setting in RSLinx and it is set to 1000ms.

When I change the UpdateRate property, it will affect the rate the data is returned. I tried setting it to 500 and the data would then only return about every half second.