https://devzone.nordicsemi.com/f/nordic-q-a/45940/bootloader-settings---current-bank-valueusing nRF52832, SDK 15.1, custom made units. My Obervations - (in bootloader settings) $nrfutil settings display ota46to47.hex when device is flashed &quot;Current bank&quot; value is 0 after first attempt of OTA, if it fails - &quot;Current bank&quot; value remainsen-USTelligent Community 13Tue, 09 Apr 2019 08:10:47 GMThttps://devzone.nordicsemi.com/thread/180930?ContentTypeID=1Tue, 09 Apr 2019 08:10:47 GMT137ad170-7792-4731-bb38-c0d22fbe4515:78ccac25-8edd-497b-815c-21c0ff4089cbAndy<p>I&#39;m not 100%&nbsp;sure about this, so take it with a grain of salt. You can test it by yourself.</p> <p>The bootloader uses the nrf_dfu_settings struct as a means to know whether a valid application is saved in bank 1. The bootloader then performs a soft-reset, and it checks whether there is a valid app in bank 1 (see&nbsp;nrf_bootloader_fw_activate() in nrf_bootloader_fw_activation.c). Then it proceeds to copy the firmware from bank 1 to bank 0.</p> <p>You can follow the code by yourself, maybe the official documentation is not great, but at least the code itself is pretty well self-documented.</p> <p>The trick to the bootloader is understanding that the applications are validated and copied <strong>on boot</strong>, not when the DFU transfer is done.</p><div style="clear:both;"></div>