DH+ Timeout

bulletin blues

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Mar 2003
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Sorry for the lack of detail but roughly, heres what happened...

I was monitoring a piece of equipment that has been acting strangly over the past couple of days. This equipment uses a AB PLC 5-25 processor.

In the shop I had a laptop set up to view the program online. I also had a desktop setup to view the same program online. Using the desktop I went to check a MSG instruction to see where a bit was coming from. When I clicked on setup, I noticed the laptop go into Data Highway Plus has timed out. The set up screen on the MSG instruction showed This Plc Data Table adress as I0000 and the length at like 23479. Ugh. I closed the setup screen and reopened it and all was well, Data Table adress n30:10 and length 10. Which is more like what I wanted to see. The desktop stayed online. The laptop was knocked offline.

We have noticed quite a few Data highway timed out errors over the past couple of days when just using the desktop,and monitoring this piece of equipment, that is why I decided to hook up the laptop. We never get a timeout error unless someone powers down the plc.

My question is, Why did the laptop go into timeout when the
desktop did not?
Anyway, Im just looking for some feedback if anyone has some.
TGIF only 2 more days to work till this work week is over!
 
BB:

I don't know if this is the same problem that you are seeing, but I was told by Rockwell support that the "DH+ timeout" warning was more of a generic warning that frequently has nothing to do with DH+. (I was getting the warning on a processor that used Ethernet, ControlNet, RIO, and ASCII - NO DH+!).

In this case, I was programming with AI software (to program CNet 1.25), and since upgrading the line and programming with RS Logix, I have not had any more "DH+ timeouts".


My only real advice is to ignore the "DH+ timeout" message, and try determining what else might be causing an error here.

I'm just guessing here, but the laptop and the desktop may have different versions of the programming software which are better or worse at handling whichever fault you are truly receiving. In fact, it doesn't have to be the specific software - it could be something else different between the two PC's (memory would be my guess).

Marc
 
just a guess ...

one thing to check is the computer's power management settings ... sometimes a computer system coughs up an electronic hairball when going into and out of these "power saving" modes ... this can occasionally cause RSLinx to hang up or otherwise "act funny" ...try disabling things like "turn off hard drives after X minutes" and "hibernation mode" etc. ... even the screensaver setting can cause problems on some systems ...

this might not have anything to do with your problem but it’s a quick and easy thing to check ... I’d give it a shot ...
 
What I have noticed is the entire DH+ network is bogging down causing all types of unpleasentries. Using RS LINX and clicking
station diagnostics I have noticed one station sending an awful lot of bad packages. The blue hose connections and cable checked out good.
Does this sound like I should change the processor or is there anything else anybody might recommend (other than a bachelors degree)
I would appreciate any feedback.
The more stuff breaks, the better I get with this stuff, go figure!
 
Two items to check.
First (which I think you know) is to make sure the laptop and desktop are both set for different DH+ address. If they are the same one of the systems will get knocked off.
Second, When you have two computers online at the same time and one goes to edit the program, the second computer will be knocked offline. Only one computer can be attached to a process at a time when the computer is editing a program. I do not know if going into a MSG blocks setup screen will do this, but it might.
 
Craig, do you think having 2 SLC 5/05 and SCADA on Ethernet and too much traffic could do loss of comms between 1 plc and HMI (RS 232)?
 
Im not sure if I want to admit this for the world to see...but...as I was saying. We have been having very strange things occur on the DH+
network. Sometimes I will check to see if I get any errors on the message blocks using the desktop. Everything seems O.K. Sometimes I use the LAPTOP to see if we have any errors on the message blocks and sure enough we do. Sometimes when I'm using the LAPTOP to see if everything is OK an operator might call and say everything seemed "sluggish" for a couple of seconds. Sometimes when I use the LAPTOP along with the desktop the desktop gets knocked offline. Something about the LAPTOP seems to be in the equation.
Now I DONT USE THE LAPTOP and everything runs smooth.
Im not sure if Im proud of this find but at least I found it.
thanx for the replies fellas
 
Bulletin Blues,
Ah, yes, you should call it the "network" blues. A certain number of this type of problems will occur on the DH+ network, and any other network. It is the nature of the beasts. Think about it: you are using the network cable so that you can connect a bunch of devices together and only have to run a few wires between them. That is great for saving wire, but not so great for reliability. I never had this class of problem before somebody invented networking. Back in the "good old days", you could predict what a piece of wire would do when you put 120 volts and one end and looked at the other end. Now, you are putting hundreds of signals on the same wire and hoping it all gets sorted out at the other end. Sometimes it doesn't and it is hard for the average fellow to know all the reasons why not. You are completely dependent on what the @#$@@ network does, and if it crashes, then you crash right along with it. Please pardon my nostalgia but sometimes I long for the simpler times.
 

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