1769-L32E Losing system time and date

Hello,
I have a compact logix 1769-L32E that intermittently loses the date and time wihtin the processor. It has reverted back to the same date multiple times. Last night it jumped a day ahead and went to the year 2114. I have 3 of these machines that are exactly the same and this is the only one doing it. I have checked the battery led's and they check out fine. Thanks for your help.

Look in your logic for a SSV instruction referencing the WALLCLOCK. That would be used to write a value to the clock. You might also see a GSV, but that would only read the clock. The SSV is the likely culprit.

When you said it reverts to the same date, that COULD mean that it is reloading from the CompactFlash card if you have one. I've never tested to see what happens with the date when you reload from the CompactFlash. I would have assumed the date would be retained but now I am wondering if it would be if it was accompanied by a power cycle. Perhaps someone here knows or can test and verify.

With the date moving forward though, that sounds as though something in your code is writing a new value to the date. That is where the SSV comes in.

You can also post the program here and we can take a look at it for you or you can Private Message it as well if you don't want the whole world to see your application.

OG

The time can be changed from the HMI through a secured screen and a push button. I had already put a trap in place to catch the number of times the button was used, thinking the operators were setting the time and not telling anyone. This turned out not to be the case. I did get a chance to talk to the operators and finally someone said that the last two times it happened they had turned off the machine. We are not using a compact flash. Im going to test this when they are done for the week. Any ideas why a power cycle would cause this if that is the case? Faulty processor?

Maybe when the HMI is powered back up its sending blank data to the PLC ?

Have you tried removing that option from the logic of the program? I would change the program and remove any/all logic that has to do with the time/date and see if it happens again, you can always add the logic back after you have proven it is or not the problem

swayne76 said:

Any ideas why a power cycle would cause this if that is the case? Faulty processor?

Click to expand...

No. But, as GIT mentions, cycling power on the HMI could have an impact.

If your HMI is able to change the date/time then it is writing that data to a set of tags in the controller, not directly to the clock itself. Then there is logic (the SSV instruction) in the controller to take that data and then write it to the controller clock.

If the HMI can write to those tags then it is also possible that something else could be writing to those tags as well. It could be other logic in that same controller, another HMI, or even another controller connected to a common network. But I would start with identifying those tags and cross-referencing to see if anything else in that controller might be affecting those tags.

OG

Quick update. Changed out the battery a month ago and so far have not had the issue happen again.