ControlLogix and OPC


Thread Starter

Jeremy Richard

I saw the previous post (Jan '01) about speed perfomance problems with Wonderware/Ingear OPC/Control Logix. But there were no answers or possible solutions. I am having an identical problem. I am running WW Intouch 7.1, OPC
Link, Ingear AB OPC Server(For WW), Control Logix 5550 with 1756-ENET/A. Network connections are routed through a switch. I currently have 2700 tags. Update speeds to the WW are extremely slow...30 sec. While
troubleshooting this problem I encountered something strange that may be the source of my problems. While the PLC is in program mode the OPC Server reads 60-100 packets per seconds, which updates my WW in about 1-2 seconds (fine).
However when the PLC is in Run mode the OPC Server reads 2-4 packets per second, which updates the WW extremely slow. Ingear has assured me that it reads the PLC tags the same if the PLC is in Run or Program. This leads me to
believe that the source of the slow update times resides in the PLC to 1756-Ethernet Card communication. Is there any way to fix this? The RPI for the Ethernet card is not configurable.

Steve Myres, PE

Another possibility is the System Overhead Time Slice, which can be set from the Advanced tab of the controller properties dialog. This is the proportion of total scan time that the processor uses to service communications and do other housekeeping as opposed to executing ladder. I believe that the out-of-the-box default is 10%.

Too low a setting will cause slow comms, expecially with a lot of tags, too high can cause faults or problems with code execution.

Also, the ENET/B or "B" revision level of the Ethernet card might have some advantage. Check with AB.

Bradley G. Hite

Hello Jeremy,

You might try changing the System Overhead Timeslice. The default value for System Overhead is 10%. I am not sure if it will have any effect on the ENET module comm timeslice but it might.

I would try a number of 20% and see if that makes any difference.

Bradley G. Hite
Intertech Inc.
mailto:[email protected]
http://www.myplc.comTeaching Practical Skills for a Technological World

Mike Patterson

Which corrected the communication problem, the new ethernet card or the System Time Slice adjustment?
Did you try using arrays (PLC side) instead of individual tags?

I'm currently working on a project using Indusoft Webstudio v4.4 SP1 for the HMI app, Ingear OPC Server (2.35.x.x) to talk to a Control Logix 5555 with 1756-ENET/B via switch. We have less 1k tags total but we have similar problem of slow update of around 5 sec. We upgraded our hardware PC & OS (now, Pentium & Win NT) and use arrays. Using arrays proved very helpful and allow us to
have an update of around 0.3 sec (we require under 0.5 s update) for our main screen that has about 50+ analog and 20+ boolean objects. In the WebStudio app, I also created several OPC worksheets dedicated (i.e., enabled/disabled)
for each particular screen. I did use Wonderware extensively in prior projects but not using an OPC server. I don't know if you can group your HMI tags so that only a subset of the tags are being updated; that is, OPC update for a group of HMI tags is enabled/disabled programmtically in the HMI app.
Ingear seems the OPC server of choice. Is there a serious problem with using WW OPCLink and RSLinx for OPC communications?

Anthony Kerstens

No. It's just that Ingear is a WW third party partner and
WW tech support will support Ingear.

For example, we recently ran into a bug, and WW gave us an interim patch for the Ingear server. They were really helpful.

Anthony Kerstens P.Eng.

Michael R. Batchelor

I can't speak to the WW product, but we have a customer that specified RSLinx for two HMI nodes (primary and backup) using VB as the client environment. Frankly it works surprisingly well for us. We monitor about 450 tags and respond to, record, or set approximately 35K data events in a typical 8 hour shift.(A PLC5/40E running a 22 station discrete assembly line, a SLC5/05 running 146 pick bins, and 8 SLC5/04s on various station's

The biggest downside I can see is that the AB OPC is (just like
MS) "enhanced" so you must use their dll instead of the one from the OPC Foundation, but it's available for free from the AB web site. My hunch is that this would prevent you from using it in a mixed OPC environment, but you might be able to strategically arrange your path and make it work.

The advantage is that we can run RSLogix5 and RSLogix500 simultaneously on the HMI node for troubleshooting. (OK, that's not the way you want the HMI to work, but it sure is convenient to just walk up to the line and see what's wrong without dragging out a laptop.)

The word on the street is that the Ingear product is faster, but I don't know. I'm pretty sure it uses the standard OPC dll's.

I am using InGear OPC with ControlLogix and Iconicx Genesis32 HMI. I have hard I/O wired to the local Logix PLC as well as SLC data via DH+ and DH-485(NET AIC). I was planning to MSG the DH+ data into Logix for access by the HMI but found I can drill directly through the ControlLogix Gateway (backplane, EtherNet/IP-DH+) to the SLC. Does this fall under the philosophy that you mentioned as not desireable in the above message?