Retentive Memory Issues

[PLCwannabe]

 Hello,

  I'm doing a lot of reading and writing to plc, working on an ongoing do-more project. Occasionally, I lose all of my retentive memory (counter acc. values, timer acc. values) etc, even if I haven't been working on those rungs that the counters or timers are on. I then have to reenter everything manually. What can cause this to happen? These values are never read or written to in the C-more, so i know they are not getting cleared by the HMI.  Any suggestions?

[ATU]

Does it come with a plastic strip on the battery to prevent discharging?

[Mike Nash]

The batteries I have seen have a tab, but it is just to help remove the battery on the Do-mores, the battery is enabled from the factory.

Look at Memory Image Manager, specifically the "Enable Automatic Download" option near the bottom left. It may be overwriting your values.

[ATU]

I guess if it was a battery issue anyway, you would get messages in the  system log. However, would the error message be lost as well?

[BobO]

If the issue is due to a failed battery, there would be a message in the system log indicating that the memory was initialized on startup. I'm wondering about the auto download as well.

[PLCwannabe]

I don't think the battery is an issue, as I am using a backup power supply. I am programming from multiple PC's though, so maybe one of the computers is the problem. Does  "enable automatic download" checkbox apply to the do-more software on a certain computer, or does it apply to a certain project?

[ATU]

Any Messages in the System Log?

[Mike Nash]

Does  "enable automatic download" checkbox apply to the do-more software on a certain computer, or does it apply to a certain project?

That's a very interesting question indeed. I do not know the answer though.

[Mike Nash]

So, I just played around with DmSim and opening a project from file vs just uploading from the PLC, and I do see a potential for maybe getting things into an awkward place. The upload-only doesn't appear to know about the memory image settings in the saved file.

[PLCwannabe]

No messages in System log. I do sometimes read project from file instead of reading directly from plc, when prompted to do so by the start-up page.

I really have never used the memory image manager. I've always assumed that retentive memory locations will keep their values, even if program changes are made. Does the software perhaps at some point decide that too many changes have been made in the program, lets clear all memory locations to zero?

[franji1]

The Memory Image manager is not enabled by default.  Also, the Download (Write) to PLC dialog would show you whether you were updating Memory Image (along with the System Configuration, Program, and/or Documentation).

If you have any regions defined in your Memory Image, then you would see an option in the Download to PLC whether to write some/all of the regions to the PLC.  It is usually UNCHECKED by default, since even if you have regions defined, you may not want to always write them (e.g. Run Mode Edit).  See the first attachment.

The 2nd attachment shows what it looks like when you do enable the Write of the Memory values - you have the option to write specific regions.

Hence, it should be obvious whether you are overwriting memory with the MIM at download time.

[ATU]

Is your event log completely empty?

[PLCwannabe]

No, it is right full.

[ATU]

Have you looked at it directly after one of these memory wipe events?

[PLCwannabe]

No I have not.Next time it happens I'll try to check all those logs to narrow down what is actually going on. If I ever figure it out what is happening I'l post it here.