https://devzone.nordicsemi.com/f/nordic-q-a/72508/setting-uicr-in-nrf51822-and-s110What is the UICR setting in nrf51822,S110? Currently, when I develop with nrf51822,S110, the UICR area is 0xFF. I want to set the UICR as follows, is there any way to set it? 　I&#39;m using keil as my development environment. 　CLENR0 : 0x18000 　XTALFREQ en-USTelligent Community 13Tue, 09 Mar 2021 12:23:28 GMThttps://devzone.nordicsemi.com/thread/298694?ContentTypeID=1Tue, 09 Mar 2021 12:23:28 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6bbe76ba-0827-4ac2-b253-db2f9e7760bfVidar Berg<p>Hello,</p> <p>I&#39;m not sure why you are able to write the XTALFREQ setting in UICR, but not CLENR0. However, I would not recommend using CLENR0 if you are using DFU as it will prevent DFU to a larger Softdevice. From the bootloader documentation:</p> <p style="padding-left:30px;"><em>If the register UICR.<span>CLENR0</span> has a size value (for example 0x00016000) and you are updating the SoftDevice, the new SoftDevice must not be larger than the current SoftDevice.</em></p> <p>Also, note that we have PAN for the 32 MHz crystal. Please refer to PAN #78 here <span><a title="nRF51822 Product Anomaly Notification v3.3" href="https://infocenter.nordicsemi.com/pdf/nRF51822_pan_v3.3.pdf?cp=5_4_1_0">nRF51822 Product Anomaly Notification v3.3</a><span> for details.</span></span></p> <p><span><span>Best regards,</span></span></p> <p><span><span>Vidar</span></span></p><div style="clear:both;"></div>