https://devzone.nordicsemi.com/f/nordic-q-a/45211/incorrect-documentation-of-gpregretIn the latest version of the v15.3 nRF SDK, the documentation states bit 1 is used as the flag to enter DFU mode. See below: // &lt;q&gt; NRF_BL_DFU_ENTER_METHOD_GPREGRET - Enter DFU mode when bit 1 (0-indexed) is set in the NRF_POWER_GPREGRET register. en-USTelligent Community 13Mon, 25 Mar 2019 16:43:51 GMThttps://devzone.nordicsemi.com/thread/178183?ContentTypeID=1Mon, 25 Mar 2019 16:43:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:ee1a4053-3956-461d-9c9e-c59831571845tesc<p>Hi,</p> <p>Thank you for pointing out this documentation error. We appreciate that! It is now registered in our internal issue tracker and should be fixed for a future release.</p> <p>Regards,<br />Terje</p><div style="clear:both;"></div>