S7-200 data retentivity

I have a s7-200 that I am using to gather some production data from a process. But if I make changes to the program I lose any gathered data (Real numbers and single letter strings that are set via a TD200C). Although all retentive counters in the program do retain their value.
The ranges are set to be retentive in the system block but I think this only applies to retentivity after a power loss.
So my question is, can I keep this data intact when I download a new modified project to the PLC...?

when you dounload new program do not dounload the data block because it will overwrite all user data

So simple when you know how....... Thankyou.
Is it just me, or is the Siemens website impossible to search and get what your looking for....? Lots on there, but a pain to navigate.
Thanks again for the info.

Gazzr said:

Is it just me, or is the Siemens website impossible to search and get what your looking for....? Lots on there, but a pain to navigate.

Click to expand...

Its not you, it takes some getting used to and even then sometimes you still cant find what you are looking for!

The other way to achieve what you want (and the way i prefer) is to create a DATA BLOCK from ram. It requires you stop the processor to upload, but at least you have the latest parameters stored.



I get into the habit of regularely doing this when commissioning, and find it's better to have a more up to date version of the offline & online files...

Hope this helps.

Rob

Thanks for the info...

Kidblue
Does this then mean that after I "Create data block from RAM" the data block on the PC will now display values stored within the PLC? I ask because this would be a quick way of capturing the current stored data that otherwise would have to be displayed in Status chart?