https://devzone.nordicsemi.com/f/nordic-q-a/6068/hardfault-with-s110Hi. I have received down the source of the example of experimental_ble_app_uart in my keil. I use register.(NRF_CLOCK-&gt;EVENTS_HFCLKSTARTED = 0;) but, Hardfault occurs. For example, main.c /**@brief Application main function. */ inten-USTelligent Community 13Tue, 17 Mar 2015 12:13:02 GMThttps://devzone.nordicsemi.com/thread/21253?ContentTypeID=1Tue, 17 Mar 2015 12:13:02 GMT137ad170-7792-4731-bb38-c0d22fbe4515:142b6018-4857-4253-980d-6b7fbb12e0f3H&#229;kon Alseth<p>Hi,</p> <p>NRF_CLOCK is a restricted peripheral when using the Softdevice. This means that you can only access it through the SoftDevice API. Please see the SoftDevice Specification for more details on which peripherals are OK to access directly.</p> <p>Use the API when the softdevice is enabled: <a href="http://developer.nordicsemi.com/nRF51_SDK/nRF51_SDK_v8.x.x/doc/8.0.0/s110/html/a01073.html#ga3e5afb495a1b0307c749cc268df94a74">developer.nordicsemi.com/.../a01073.html</a></p> <p>Cheers, Håkon</p><div style="clear:both;"></div>