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  1. #1
    Join Date
    May 2009
    Posts
    639

    ALC OEM modbus IP weirdness

    I thought I posted something ages ago but I can't find it now. Having some trouble with modbus IP.

    Symptoms, basically some points stop reading and some work fine.
    -analog trends have perfectly flat graphs that never change.
    -digital alarms don't work.
    -under point properties the refresh time is observed as being zero and never changes. (see attached picture)
    -points that are frozen like this just deceptively remain at their last read value.
    -modscan32 reads the equipment just fine while this is happening.
    -after a power cycle or zap on the module all the above troubles go away, for a while. Sometimes works fine for hours or days but eventually some points stop working.
    -while this happens there are plenty of points that work fine too. Plenty of sites that don't have the problem at all as well.

    I don't see any evidence I recognize in the modstat, the last modbusIP status is generally connection made error 0.

    Generally the IP point counts are fairly low like 20-60 somewhere which means the program execution rates are generally up in the thousands so it isn't like we are overloading the module.

    I have OEMctrl working on this for a long time now. We have replicated the problem in our lab using modsim32.
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    Scott Jalbert
    Harris Integrated Solutions

    Formerly Liebert (Emerson Network Power)
    Expressed opinions are my own

  2. #2
    Join Date
    Dec 2005
    Location
    California
    Posts
    313
    Good luck getting an answer. It's not an OEM problem but an ALC problem. I've been having similar issues since 2004. Increasing and staggering the update times solves the issue most of the time. ALC told me many times over the years they where developing a new driver to correct this issue. Still waiting.

  3. #3
    Join Date
    May 2009
    Posts
    639
    Do you have baselines on how much seperation time between point refresh times is necessary and works for you?

    Also if I have say seven copies of the same equipment file (each reading a different slave/IP) would I have to stagger the one point across those seven copies of equipment file too?
    Scott Jalbert
    Harris Integrated Solutions

    Formerly Liebert (Emerson Network Power)
    Expressed opinions are my own

  4. #4
    Join Date
    Dec 2007
    Location
    Hopkins, South Carolina
    Posts
    159
    They do have a new modbus driver in beta right now

  5. #5
    Join Date
    May 2009
    Posts
    639
    We confirmed the problem is in drv_prtlpro_xmm_2-02-001.driver, drv_prtlpro_xmm_3-05-068.driver and drv_prtlpro_xmm_3-05b-002.driver. I personally haven't checked the drivers between those but if it is in the two newest and the oldest I have...

    We were just given a drv_prtlpro_mb_combo_2-26-002.driver that is beta and not supposed to be used on sites yet but haven't had time to test it yet. This driver caught my interest because you can change the modbusIP port number from 502 to something else. Also the timing section is very different from all others so I hold some hope on this one, obvious that there has been some work done.
    Scott Jalbert
    Harris Integrated Solutions

    Formerly Liebert (Emerson Network Power)
    Expressed opinions are my own

  6. #6
    Join Date
    Dec 2005
    Location
    California
    Posts
    313
    It depends on field conditions. I would update none critical info at the highest possible update times. Set the update times 1:00, 58,57,56,55,54 then critical info for faster rates. The driver defaults at 1:00 polling rate. This can easily crash a third party device on some large systems.
    Your point count seems quite small, so that should work. I've had to use multi LGR-250 instead of LGR-1000. For reasons unknown a LGR-1000 would crash when loaded up, but (4) 250 didn't. But the same LGR-1000 worked fine when loaded up on other devices.
    Hope the new driver works. 2.24 was so hot

  7. #7
    Join Date
    Jul 2005
    Location
    Pittsburgh, PA
    Posts
    258
    I just had the same problem between ALC and Liebert PDUs. We were using a beta driver, it worked for a while and quit. Modscan showed good data but on the ALC side every modbus point, and I'll use 40010 for an example, showed the same data whether it was 40010/1 or 40010/2 and so on. We got a newer ALC beta driver and everything is now good.
    HotRod


    Controls..some days your a hero, some days your a zero. Direct acting since 1992.

  8. #8
    Join Date
    May 2009
    Posts
    639
    Quote Originally Posted by hotrod53 View Post
    I just had the same problem between ALC and Liebert PDUs.
    To my knowledge our PDU's are 485 RTU only and don't do modbus IP slave so this sounds like something else entirely.
    Scott Jalbert
    Harris Integrated Solutions

    Formerly Liebert (Emerson Network Power)
    Expressed opinions are my own

  9. #9
    I also face problem in interfacing between ALC and PLC using Modbus TCP
    Control$ : Why and how ALC can crash third party modbus tcp device?
    The problem I facing is the ALC cause the modbus tcp slave hang up. Anyone experience on this?

    What is the latest modbus tcp driver version for LGR-1000?
    Any remaining issues?

  10. #10
    Join Date
    May 2009
    Posts
    639
    I don't know if they released the driver on the ALC side yet but we are working with a combo driver in the 4.x.x range for 5 and below that looks like it fixes the IP problems we had. Tested on three or four sites now without issue as in it fixed the refresh problem and didn't create any new ones.
    Scott Jalbert
    Harris Integrated Solutions

    Formerly Liebert (Emerson Network Power)
    Expressed opinions are my own

  11. #11
    Join Date
    Dec 2005
    Location
    California
    Posts
    313
    nscc,

    ALC does not crash the third party device. What happens is the ALC LGR "locks up". It stopped updating and does not generate any sort of error. Sounds like what you've described. It was frustrating when ALC stopped, and I still saw the vintage '98 Modicon still updating on a well used CRT.
    ALC been working on a new driver for years to solve this issue (and others). The lastest beta is drv_melgr_mb_combo_2-26-013.driver. So far it's been working great. No hangups.

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