https://devzone.nordicsemi.com/f/nordic-q-a/31273/bootloader-being-written-to-application-address-after-dfuThe nrfgprgret register is used from the application(custom) to trigger the system into dfu mode. The nrf 52 enters dfu mode and a zip file containing bootloder.bin/.dat and manifest is successfully transferred. But the bootloader(custom) is being writtenen-USTelligent Community 13Mon, 12 Mar 2018 14:45:08 GMThttps://devzone.nordicsemi.com/thread/123978?ContentTypeID=1Mon, 12 Mar 2018 14:45:08 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0affe1b2-c189-4cf5-bcb4-fd4afa981617Bj&#248;rn Kvaale<p>Hi Atharva,</p> <p>1) It is not possible to change the BOOTLOADER_START_ADDR unfortunately. This address is set in the UICR.NRFFW[0] register&nbsp;location &amp; remains static (<a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v14.2.0/lib_bootloader.html?cp=4_0_0_3_5_0_1#lib_bootloader_memory" target="_blank" rel="noopener noreferrer">see link</a>). The BOOTLOADER_START_ADDR is not changed during the DFU process. It is only defined&nbsp;when the chip is programmed during production.</p> <p>2) No changes are required.</p> <p>It might be useful for you to take a look at the <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v14.2.0/lib_bootloader_dfu_banks.html?cp=4_0_0_3_5_1_2" target="_blank" rel="noopener noreferrer">dual bank &amp; single bank update processes located here</a>. Also, what changes are you making to your custom bootloader compared with the regular bootloader (i.e. bootloader_secure_ble)?</p> <p>Kind Regards,</p> <p>Bjørn Kvaale</p><div style="clear:both;"></div>