S7-300 Data Retention

Is there any other reason besides re-downloading that I would be losing my actual values and reverting to my initial values in my DB's with a power outage? Note: They are not Instance DB's. and my battery is good.

Marek

Perhaps you haven't specified the DB areas as memory retentive.

In the hardware setup screen, right click the CPU and select object properties, select the retentive memory tab, and here you can specify what DB area you want to be retentive.

Paul

That is why I specified that the battery was good. I believe that all non-Instance DB's are retentative if the battery is installed using an S7-300.

Marek Tenerowicz said:

I believe that all non-Instance DB's are retentative if the battery is installed using an S7-300.

Click to expand...

'fraid not Marek,

You have to specify what you want as retentive.
see the picture below for the 'default' settings

Paul

Doesn't this mean that I do not need to define the retentative areas in the Hardware config?

"Retentive Memory" Tab

Meaning of the tab for S7-300:
In the "Retentive Memory" tab, you can specify which memory areas are to be retained following power failure and after a transition from STOP to RUN, even without a battery backup (in the backup memory of
the CPU). If a backup battery is inserted, data blocks are always retentive.

Meaning of the tab for S7-400:
Requirement for retentivity is a backup battery being inserted. In the "Retentive Memory" tab you can set which addresses (bit memory, S7 timers, S7 counters) are to be retained following a warm restart; data blocks are always retentive. With a hot restart all address areas and data blocks are retentive.

The following items can be retentive:
Number of memory bytes from MB0
Number of S7 timers from T0 (not relevant for M7)
Number of S7 counters from C0 (not relevant for M7)

Only relevant for S7-300 (without battery backup):
Data areas of data blocks, so-called retentive areas.

Note
Edit Parameters

Marek

What you quoted does sound like you don't have to define the retentive memory areas for DB's, but unless you specify what you want as retentive in the hardware setup, then only the default areas (as shown in the picture I posted) are loaded into the system data for the CPU.

Paul

I'm with Marek on this one. I have never defined a retentive DB in an S7-300 but my values stay stable as long as my battery is good. That's typically why I have used DBs for config data.

Marek, are you using an external memory module with this processor? I recently had something similar to this happen on one of three S7-314 plcs. Ultimately I fixed it by loading in the program from one of the other supposedly identical plcs. This led me to believe, although I didn't check into it, that there is a system setting that will force a memory module load on processor start and I had inadvertently set this on one of the three machines.

Then again, if you don't use a memory module, I don't know what to tell you. Other than the one occurance I haven't come across this.

Keith

Keith

I might well stand corrected on this point, the last project I done with a 315-2 DP, without a memory module, I needed some DB data to be retentive (some counters and run timers), upon testing the program I did find that I lost my data until I specified the areas in the hardware configuration.

Paul

I will try it, but is there any way that I can save my current active values before I re-download the hardware config? At that point I will lose the ones I have.

I am using a 318-2 with a memory module. The Startup is set to warm restart. If anyone can find a system setting that may help me I would appreciate it. Untill then I will try to set the retentive area in the hardware config and hope it helps.