When I flash an update of my code, does the stored flash data get erased?

[brianreinhold]

I am having problems writing to flash in an older version of s110 using the sd_flash_write() method. The question I have is when I update my code, make a new build, and download the new code to the nRF51822, does the data I have previously written to flash memory also get erased?

I am using Keil. I see that an erase is performed before the download but I don't know if that is just the code or if my previously written data gets erased as well. If the flash data I have written is NOT erased, how do I erase it? Is there a difference between the 'erase' option only and the 'download' option which also erases?

I am using flash to save bonding data. So I need to know the state of the flash when I make a new update (should I clear the bonding information on the central?).

Thanks.

[Hung Bui]

Hi Brian, 
It's depends on the option you selected in Keil Target setup. 

If you choose Erase Full chip, any application data will be erased. If you choose Erase Sectors only the sectors that your application occupies (the firmware) will be erased. 

So if you have stored bond information, and you select Erase Sectors, then bond info  will retain. 

[brianreinhold]

If I select 'Erase Full Chip' does that include SoftDevice as well? So there are three things

1. SoftDevice

2. Application

3. Data persistently stored by the application such as LTKs for bonding

Is that controlled by the programming algorithm? (It was never clear to me what 'programming algorithm' was.)

[Hung Bui]

Yes, correct. If you choose "erase full chip" the softdevice will be erased. 
The algorithm is the Jlink algorithm used by Keil to flash. 
This option is equal to calling nrfjprog.exe of --chiperase or --sectorerase when you do nrfjprog --program.

[brianreinhold]

Okay, How can I erase the stuff I write (my application and data associated with my application) but NOT SoftDevice?

[Hung Bui]

You would need to erase the pages you use manually using nrfjprog, it's because the programmer wouldn't know where your application data is. 
What we usually do is to do a full erase, then flash softdevice then flash application. You can create a .bat file to execute the tasks automatically.