https://devzone.nordicsemi.com/f/nordic-q-a/92358/nrf52840-readback-protection-after-resetHi, Build an application without SD but with MBR. MBR is at address 0x0000 - 0x1000. Application is at 0x1000 - 0xF0000. At the beginning of the application is the ISR vector. Application is also working after programming. However after a reseten-USTelligent Community 13Tue, 27 Sep 2022 13:03:29 GMThttps://devzone.nordicsemi.com/thread/388152?ContentTypeID=1Tue, 27 Sep 2022 13:03:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:082dca75-48ee-4117-85a0-82d6de8758feLecram69<p>Seems like it is rev 3 nRF52840. Thanks!</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/388128?ContentTypeID=1Tue, 27 Sep 2022 12:00:09 GMT137ad170-7792-4731-bb38-c0d22fbe4515:54393ad3-7eba-4254-a0da-e7e065fe05e0Hung Bui<p>Hi Marcel,&nbsp;</p> <p>If you are using <a href="https://infocenter.nordicsemi.com/topic/comp_matrix_nrf52840/COMP/nrf52840/nRF52840_ic_revision_overview.html?cp=4_0_3_0">revision 3 of nRF52840 chip (Fx0)</a> the readback protection is enable by default after a reset if it&#39;s not disabled by the software. Please have a look <a href="https://infocenter.nordicsemi.com/topic/ps_nrf52840/dif.html?cp=4_0_0_3_7_1#concept_udr_mns_1s">here.</a></p> <p>So it&#39;s normal that the application goes into readback protection if you don&#39;t disable it in the software.&nbsp;</p> <p>If you want to disable APPROTECT, please follow the instruction in the documentation.&nbsp;</p><div style="clear:both;"></div>