RAM data is retained without power?

[maxx44]

SDK: 17.0.2

IDE: SES

nRF52832 module

Hi!

I have a nRF52832 based custom board operating on battery power.  I assigned a variable to the non_init section in SES and loaded a value.  I expected this would disappear if I disconnected power, so I unhooked the battery and powered off the connected nRF52 DK.  And I closed SES.  Then I powered up everything and ran the debugger to the point where I read my non_init variable from RAM.  It still had the data I wrote!  What gives?  Shouldn't this value have disappeared when powered down?

So I thought I would leave a few hours  go by in case there was a cap holding the RAM data active.  After something like 4 hours I still read the the value I wrote into the non_init RAM.

What I'd like to do is have some method to detect an initial power on reset state after connecting power and set some initial conditions for the application that will be used as long as power is on .... such as date and time.  Let me know if you can suggest a good way to do this.

Thanks!

Max

    

[maxx44]

Thanks!!!

I'm going to give this a try and see if I can work it in to my application.  May take a day or 2.  So far what you presented above compiles.  Some additions for the one time code and testing to follow.  I'll report back.

Yes, I am using the standard section placement file .... hopefully I'll be OK with that. 

Max

[maxx44]

I was able to verify this method works.  Good work and thanks again!

I was trying something very similar, but just placed a code in the .non_init variable versus reading the RTC device ID.  I wasn't able to step through with the debugger, but as you pointed out it works OK if you disconnect the J-Link and just run on the board cycling power.

I'll mark your post as the verified answer.