https://devzone.nordicsemi.com/f/nordic-q-a/41327/the-reset-value-of-pselreset-in-nrf52840-why-not-is-0xffffffff-but-0x0012-and-how-can-i-change-itHi, I want to use the p0.18 as a GPIO without being connected to nRESET function. So I removed &quot;CONFIG_GPIO_AS_PINRESET&quot; from the define option in Keil. And then i found that the reset value of PSELRESET was still been set as 0x0012 when I debugged theen-USTelligent Community 13Fri, 07 Dec 2018 13:58:52 GMThttps://devzone.nordicsemi.com/thread/160759?ContentTypeID=1Fri, 07 Dec 2018 13:58:52 GMT137ad170-7792-4731-bb38-c0d22fbe4515:92baf0a6-bbb7-49f3-a23f-2c33c671fe60Hung Bui<p>Hi,</p> <p></p> <p>You would need to erase the UICR&nbsp;to change the PSELRESET value to 0xFFFFFFFF. The write command can only change from bit 1 to bit 0.&nbsp;</p> <p>Make sure you back up other value in the UICR and re-write them back .&nbsp;</p><div style="clear:both;"></div>